Official Statistics

30 day all-cause mortality following MRSA, MSSA and Gram-negative bacteraemia and C. difficile infections: 2022 to 2023 report

Updated 9 November 2023

Main findings

There has been a small increase in both the case fatality rate and mortality rate of all infections in financial year 2022 to 2023 compared to financial year 2021 to 2022, with the exception of meticillin resistant S. aureus (MRSA). These rates remain elevated to pre-COVID-19 pandemic levels observed in financial year 2018 to 2019. Notably, since the start of the surveillance, the overall case fatality rate has seen a 34.8% decline, while the overall mortality rate has also decreased, by 11.8%.

A slowly increasing trend has been observed in the mortality rate of community-onset (CO) Escherichia coli (E. coli) bacteraemia between April 2012 and March 2020, which declined in financial year 2021 to 2022 and increased again in financial year 2022 to 2023. The mortality rate of hospital-onset (HO) cases, on the other hand, has been relatively stable since April 2012, with the exception of financial year 2020 to 2021, when a slightly steeper rise was seen. Of note, mortality rate and case fatality rates (CFR) have returned to pre-pandemic levels, despite incidence remaining lower than pre-pandemic levels.

There has been a relatively stationary mortality rate in CO Klebsiella species (Klebsiella spp.) bacteraemia, since the start of surveillance in April 2017. This contrasts with the mortality rate of hospital-onset cases which was similarly stable until financial year 2020 to 2021, when a large increase was observed, coinciding with the start of the COVID-19 pandemic. Following this peak, the mortality rate for HO cases has continued to decline but remains above pre-pandemic levels for hospital-onset deaths.

Fluctuating mortality rates and CFR have been observed for Pseudomonas aeruginosa (P. aeruginosa) bacteraemia within a relatively consistent range, except for a peak in HO mortality rate and CFR in financial year 2020 to 2021.

A substantial decline in the mortality rate and case fatality rate of meticillin-resistant Staphylococcus aureus (MRSA) bacteraemia was observed over the surveillance period, affecting both hospital-onset and community-onset cases.

The mortality rate of meticillin-susceptible Staphylococcus aureus (MSSA) bacteraemia has increased in recent years, primarily driven by an increase in the mortality rate of community-onset cases, which reached a peak in financial year 2022 to 2023. Despite a sharp rise in case fatality rate during financial year 2020 to 2021, this declined in the following financial year. Case fatality rate for HO cases resumed a general downward trend, while remaining relatively stable for CO cases. Notably, the case fatality rate in both settings remained above pre-COVID-19 pandemic levels.

A substantial decline in the mortality rate of Clostridioides difficile infections (CDI), especially for HO cases, since the start of surveillance in April 2007, until financial year 2019 to 2020, after which year-on-year increases were observed, coinciding with a marked increase in incidence rates.

This report presents data on the 30-day all-cause mortality following MRSA, MSSA bacteraemia, E. coli bacteraemia, Klebsiella spp. bacteraemia and P. aeruginosa bacteraemia and CDI. All data tables associated with this report are included in an Open Document Spreadsheet. This also marks the final annual mortality report, as starting with the financial year 2022 to 2023 report, mortality data has been integrated into the annual epidemiological commentary.

Data in this report is presented as 30-day all-cause mortality rate and case fatality rates (CFR). Mortality rate is a widely used outcome for assessing risk of death. The mortality rate is the number of deaths divided by the population at risk. The CFR is the number of deaths as a percentage of all reported cases. This provides a measure for comparing survivability of different infections.

This report presents data on all-cause mortality, and therefore include deaths that may not be directly attributable to the infections.

Data throughout this report is presented in financial years, with the years starting in April and ending in March. Hereafter, the month names will be omitted and ‘financial year’ will be abbreviated to ‘FY’ for brevity purposes, such that the most recent financial year will be described as ‘FY 2022 to 2023’, rather than ‘financial year April 2022 to March 2023’.

Between the FY 2021 to 2022 and FY 2022 to 2023, with the exception of MRSA and MSSA bacteraemia, the CFR increased for all other data collections:

• E. coli bacteraemia increased from 15.0% to 15.9%
• Klebsiella spp. bacteraemia increased from 19.5% to 19.6%
• P. aeruginosa bacteraemia increased from 25.0% to 25.6%
• MRSA bacteraemia decreased from 26.2% to 22.5%
• MSSA bacteraemia decreased from 22.1% to 21.9%
• C. difficile infection increased from 13.7% to 13.8%

Comparing across FY 2021 to 2022 and FY 2022 to 2023, with the exception of MRSA bacteraemia, the mortality rate (expressed in deaths per 100,000 population per financial year) increased for all data collections:

• E. coli bacteraemia from 10.1 to 10.9
• Klebsiella spp. bacteraemia from 3.9 to 4.1
• P. aeruginosa bacteraemia from 1.9 to 2.0
• MRSA remained at 0.3
• MSSA bacteraemia increased from 4.8 to 5.1
• C. difficile infection increased from 3.5 to 3.8

Between March 2020 and March 2022, England experienced 3 major waves of COVID-19 infection. During the early part of the pandemic many elective procedures in hospitals were cancelled, leading to reduced hospital activity. During this decline in hospital activity, reductions were also observed in the number of Gram-negative and S. aureus bacteraemia and CDI reported during this period. A small increase in CFR was observed across all organisms in the first year of the COVID-19 pandemic followed by a decrease in FY 2021 to 2022. It is unclear how much of the increase in CFR during the first pandemic year could be attributed to COVID-19 but 21% of CDI cases had a positive COVID-19 test in the 4 weeks before or after CDI positive sample at this time, as described in the FY 2021 to 2022 version of this report.

Results for all mandatory surveillance infections

During FY 2022 to 2023, there were a total of 84,484 cases of E. coli, Klebsiella spp., P. aeruginosa, MRSA and MSSA bacteraemia, and CDI in England. This was an increase of 4.4% from the previous year’s total of 80,913 (FY 2021 to 2022). There were 83,299 (98.6%) cases that could be linked to NHS Spine data to obtain mortality information. There were 14,621 deaths within 30 days of taking a specimen (blood culture for bacteraemia, faecal sample for CDI), with highest number of deaths (6,087 deaths) associated with E. coli, which represented 41.6% of deaths covered by this report. The overall mortality rate was 26.2 deaths per 100,000 population, with a CFR of 17.6% (Table S1 of the supplementary data set and Figure 1).

The number of deaths has increased from FY 2021 to 2022 (13,574 deaths) to FY 2022 to 2023 (14,621 deaths). The mortality rate and CFR have increased by 1.7 deaths per 100,000 population and 0.5%, respectively.

Figure 1. 30-day all-cause case fatality rate by infection, FY 2007 to 2008 to FY 2022 to 2023

Escherichia coli bacteraemia

During FY 2022 to 2023, 38,757 E. coli bacteraemia cases were reported in England. Information on mortality was available for 98.6% (38,197) of these cases (Table S2 of the supplementary data set). There were 6,087 deaths within 30 days of an E. coli bacteraemia, indicating a mortality rate of 10.9 deaths per 100,000 population and a CFR of 15.9%.

There was an initial declining trend in CFR, starting from 16.8% in FY 2012 to 2013 reaching its lowest point of 13.9% in FY 2018 to 2019, after which the CFR increased to 16.0% by FY 2020 to 2021. The mortality rate increased between FY 2012 to 2013 and FY 2019 to 2020 from 9.7 to 11.0 deaths per 100,000 population; it then declined in the 2 subsequent years but returned to a level similar to the peak, at 10.9 deaths per 100,000 population in FY 2022 to 2023.

Variation by onset of bacteraemia

The mortality rate of HO cases increased from 4.8 deaths per 100,000 bed-days during FY 2019 to 2020 to 5.3 deaths per 100,000 bed-days during FY 2020 to 2021, coinciding with the COVID-19 pandemic. The HO mortality rate subsequently decreased to 4.7 deaths per 100,000 bed-days in FY 2021 to 2022, before increasing slightly in FY 2022 to 2023 to 4.9 deaths per 100,000 bed-days (Table S3 of the supplementary data set and Figure 2). The surveillance of CO mortality rate reached an initial peak of 7.7 deaths per 100,000 population during FY 2019 to 2020. It subsequently decreased to 7.1 in FY 2021 to 2022 and later returned to 7.7 in FY 2022 to 2023 (Table S3 of the supplementary data set and Figure 2).

The CFR of HO cases declined from 23.6% to 22.2% between FY 2012 to 2013 and FY 2022 to 2023. CO cases also showed a decline in CFR from 14.8% to 14.3% over the same period (Table S3 of the supplementary data set and Figure 3). However, these reductions were not constant throughout the period, with a peak of 22.9% for HO CFR, and a peak of 14.6% for CO CFR, in FY 2020 to 2021, which also coincided with the start of the COVID-19 pandemic; these increases came after the lowest CFR levels were observed, with 12.3% for HO CFR in FY 2018 to 2019, and 21.2% observed in FY 2016 to 2017 for CO CFR. In the most recent FY 2022 to 2023, CFR of CO cases increased from 13.3% in the previous year to 14.6%, while the CFR for HO cases decreased from 22.6% in the previous year to 22.2%.

Figure 2. 30-day all-cause mortality rate of hospital-onset and community-onset E. coli bacteraemia, FY 2012 to 2013 to FY 2022 to 2023

Figure 3. 30-day all-cause case fatality rate of E. coli bacteraemia by onset, FY 2012 to 2013 to FY 2022 to 2023

Variation by NHS commissioning region

During FY 2022 to 2023, regional mortality rate ranged from 8.3 deaths per 100,000 population in London to 13.8 deaths per 100,000 population in North East and Yorkshire, which corresponds to relatively high infection rates observed in the North East region (as reported in the annual epidemiological commentary). Over the same period, CFRs ranged from 13.8% in London to 17.2% in the Midlands (Table S4 of the supplementary data set).

Variation by age and sex

Mortality rate and CFR generally increased with age and was greater in male cases than female cases. However, for cases under the age of one year, the mortality rate was higher than those aged 45 to 64 years, and for female cases under the age of one, the CFR was higher compared to those aged 15 to 44 years. In previous years, male cases under the age of one also showed higher CFR compared to those aged 1 to 14 years (Table S5 of the supplementary data set, Figure 4 and Figure 5).

During FY 2022 to 2023, among male cases, the highest mortality rates were in those aged 85 years and over (200.5 deaths per 100,000 population) and those aged 75 to 84 years (70.4 per 100,000 population), which equated to CFRs of 24.7% and 18.6%, respectively. Additionally, the mortality rate increased between FY 2021 to 2022 and FY 2022 to 2023 in all age groups except in the 15 to 44 years group. However, numbers of deaths are very small in this age group so differences should be interpreted with caution.

During FY 2022 to 2023, among female cases, the highest mortality rates were seen in those aged 85 years and over at 105.4 per 100,000 population and in those aged 75 to 84 years at 40.3, with a CFR of 20.9% and 14.7% of cases, respectively. The mortality rate and CFR in those aged under the age of 1 increased from FY 2021 to 2022, with mortality rate for females increasing from 5.8 to 7.8 per 100,000 population and CFR increasing from 8.9% to 9.5% of cases. Mortality rates and CFRs also marginally increased in females aged between 1 to 14 years, although numbers of deaths are small in this group, so differences should be interpreted with caution.

Figure 4. 30-day all-cause mortality rate of E. coli bacteraemia by age and sex, FY 2012 to 2013 versus FY 2022 to 2023

Figure 5. 30-day all-cause case fatality rate of E. coli bacteraemia by age and sex, FY 2012 to 2013 versus FY 2022 to 2023

Klebsiella species bacteraemia

During FY 2022 to 2023, 11,823 Klebsiella spp. bacteraemia cases were reported in England. Information on mortality was available for 98.3% (11,617) of these cases (Table S6 of the supplementary data set). There were 2,281 deaths within 30 days of a Klebsiella spp. bacteraemia giving a mortality rate of 4.1 deaths per 100,000 population. The CFR was 19.6%.

Mandatory surveillance of Klebsiella spp. bacteraemia started during FY 2017 to 2018, meaning trends are not as established as those in data collections such as MRSA or E. coli bacteraemia. The mortality rate increased from 3.4 to 4.1 deaths per 100,000 population between FY 2017 to 2018 and FY 2022 to 2023. Conversely, the CFR decreased from 20.2% (1,896 deaths) to 19.6% (2,281 deaths) between FY 2017 to 2018 and FY 2022 to 2023. The observed decrease in CFR is due to an increase in incidence, despite the increase in the number of deaths.

A large increase in CFR was observed between FY 2018 to 2019 and FY 2020 to 2021, coinciding with the COVID-19 pandemic, increasing from 18.7% to 21.8%. The mortality rate also increased over the same period, from 3.5 to 4.3 deaths per 100,000 population.

Variation by onset of bacteraemia

The mortality rate of HO cases increased from 2.0 deaths per 100,000 bed-days (688 deaths) during FY 2017 to 2018 to 3.6 deaths per 100,000 bed-days (990 deaths) during FY 2020 to 2021. It subsequently declined to 2.6 deaths per 100,000 bed-days in FY 2022 to 2023, which still remains above the rate observed prior to the start of the COVID-19 pandemic (Figure 6). Over the same period, the mortality rate in CO cases has fluctuated between 2.2 to 2.4 deaths per 100,000 population in the period between FY 2017 to 2018 and FY 2022 to 2023, sitting at 2.4 in FY 2022 to 2023 (Table S7 of the supplementary data set and Figure 6).

Between FY 2017 to 2018 and FY 2022 to 2023, the CFR of HO cases decreased from 24.5% to 23.6% of cases, despite a peak of 27.1% in FY 2020 to 2021. Compared to the start of surveillance, the CFR in CO cases decreased from 18.3% to 17.7% (Table S7 of the supplementary data set and Figure 7).

Figure 6. 30-day all-cause mortality rate of hospital-onset and community-onset Klebsiella species bacteraemia, FY 2017 to 2018 to FY 2022 to 2023

Figure 7. 30-day all-cause case fatality rate of Klebsiella species bacteraemia by onset, FY 2017 to 2018 to FY 2022 to 2023

Variation by NHS commissioning region

During FY 2022 to 2023, regional mortality rates ranged from 3.1 deaths per 100,000 population in South West to 5.2 deaths per 100,000 population in North East and Yorkshire, which corresponds to relatively high infection rates observed in the North East region and lower infection rates observed in parts of the South West region (as reported in the annual epidemiological commentary). Over the same period, CFRs ranged from 18.1% in South West to 20.5% in North East and Yorkshire (Table S8 of the supplementary data set).

Most regions saw an increase in CFR in FY 2022 to 2023 compared to FY 2021 to 2022, with the exception of London and Midlands, where the CFR declined from 20.2% to 18.6% and 21.8 to 20.4%, respectively. Mortality rates increased for the East of England (3.1 to 3.7 deaths per 100,000 population), North East (4.6 to 5.2), North West (3.8 to 4.2) and South East (3.4 to 3.8); they remained the same for London (4.4), and decreased for the Midlands (3.8 to 3.6) and South West (3.3 to 3.1).

Variation by age and sex

During FY 2022 to 2023, the mortality rate and CFR increased with age, except among those under the age of one year. The mortality rate was greater in male cases while the CFR was greater in female cases in most age groups (Table S9 of the supplementary data set, Figure 8 and Figure 9).

Among male cases, the highest mortality rates were in those aged 85 and over (70.4 deaths per 100,000 population) and those aged 75 to 84 years (28.5 deaths per 100,000 population), and equated to CFRs of 27.5% and 20.8%, respectively. Both the mortality rates and the CFRs increased in these age groups compared to FY 2021 to 2022, where the mortality rate was 60.3 deaths per 100,000 population in those aged 85 and over and 24.2 deaths per 100,000 population in those aged 75 to 84 years; the CFR was 26.0% in those aged 85 and over and 19.6% in those aged 75 to 84 years.

In female cases, the mortality rates were 24.3 deaths per 100,000 population (85 years and over) and 12.3 deaths per 100,000 population (those aged 75 to 84 years). CFRs for these groups were 31.9% and 22.7%, respectively. Like trends seen in male cases, the mortality rate and CFR were higher than in the previous financial year, where the mortality rate was 21.3 deaths per 100,000 population and the CFR was 27.6% for females aged 85 years and over. An increase was also observed in females aged 75 to 84 years compared to the previous year, where the mortality rate was 11.2 deaths per 100,000 population and the CFR was 22.5%.

Figure 8. 30-day all-cause mortality rate of Klebsiella species bacteraemia by age and sex, FY 2017 to 2018 versus FY 2022 to 2023

Figure 9. 30-day all-cause case fatality rate of Klebsiella species bacteraemia by age and sex, FY 2017 to 2018 versus FY 2022 to 2023

Pseudomonas aeruginosa bacteraemia

During FY 2022 to 2023, 4,409 P. aeruginosa bacteraemia cases were reported in England. Information on mortality was available for 98.4% (4,339) of these cases (Table S10 of the supplementary data set). There were 1,111 deaths within 30 days of a P. aeruginosa bacteraemia, giving a mortality rate of 2.0 deaths per 100,000 population and a CFR of 25.6%.

Mandatory surveillance of P. aeruginosa bacteraemia started during FY 2017 to 2018, meaning trends are not as established as those in data collections such as MRSA or E. coli bacteraemia. The CFR decreased from 26.9% (1,121 deaths) during FY 2017 to 2018 to 25.6% (1,111 deaths) during FY 2022 to 2023. The mortality rate in FY 2022 to 2023 remained the same as in FY 2017 to 2018, at 2.0 deaths per 100,000 population, with some fluctuation in the intervening years.

The mortality rate and CFR of P. aeruginosa bacteraemia increased during surveillance in FY 2020 to 2021, compared to the previous year, subsequently, the CFR decreased from 27.7% during FY 2020 to 2021 to 25.0% during FY 2021 to 2022 before increasing in FY 2022 to 2023 to 25.6%.

Variation by onset of bacteraemia

During FY 2022 to 2023, the mortality rate of HO cases increased to 1.4 deaths per 100,000 bed-days (482 deaths) compared to 1.3 (430 deaths) in FY 2021 to 2022) (Table S11 of the supplementary data set and Figure 10). Over the same period, the mortality rate in CO cases remained stable at 1.1 deaths per 100,000 population (629 deaths and 631 deaths, respectively) (Figure 10).

Between the start of surveillance (FY 2017 to 2018) and FY 2022 to 2023, the CFR of HO cases decreased from 29.9% to 29.0%. During FY 2020 to 2021, the CFR or HO cases peaked at 33.9%, before declining to 27.0% the year after. While for CO cases we observed a decrease from 25.1% to 23.5% of cases, although the initial decrease was seen from FY 2018 to 2019, after which we see year-to-year fluctuations (Table S11 of the supplementary data set and Figure 11). Compared to the previous FY 2021 to 2022, CFR in HO cases increased from 27.0% to 29.0%, but declined slightly in CO cases, from 23.8% to 23.5%.

Figure 10. 30-day all-cause mortality rate of hospital-onset and community-onset Pseudomonas aeruginosa bacteraemia, FY 2017 to 2018 to FY 2022 to 2023

Figure 11. 30-day all-cause case fatality rate of Pseudomonas aeruginosa bacteraemia, FY 2017 to 2018 to FY 2022 to 2023

Variation by NHS commissioning region

During FY 2022 to 2023, regional mortality rate ranged from 1.8 deaths per 100,000 population in South West to 2.1 deaths per 100,000 population in North East and Yorkshire (Table S12 of the supplementary data set). Over the same period, CFRs ranged from 20.2% in London to 30.0% of cases in North West.

Variation by age and sex

During FY 2022 to 2023, mortality rate and CFR generally increased with age, except among those under the age of one year. Notably, male cases aged 45 to 64 years had a higher CFR compared to the 65 to 74 age group. The mortality rate was greater in male cases, while the CFR was greater in female cases in all age groups except for children under the age of one year (Table S13 of the supplementary data set, Figure 12 and Figure 13).

During FY 2022 to 2023, among male cases, the highest mortality rates were those aged 85 years and over (27.2 deaths per 100,000 population) and those aged 75 to 84 years (13.2 deaths per 100,000 population), which corresponded to CFRs of 27.4% and 26.0% of cases, respectively. The next highest CFR was in male children under the age of one year, at 25.0%.

In female cases of the same age groups, the mortality rates were far lower than their male counterparts; 13.6 deaths per 100,000 population (85 years and over) and 6.7 deaths per 100,000 population (75 to 84 years). These equated to CFRs of 45.8% and 37.8% of all cases in these age groups, which were higher than the CFRs of male cases of the corresponding age groups.

Among children aged less than one, the mortality rate in male cases was 2.9 deaths per 100,000 population (25.0% of cases) compared to 1.4 (19.0% of cases) in female cases. We also note an increase in CFR in the male 1 to 14 age group compared to FY 2017 to 2018. However, caution is required in interpreting this data, as the number of deaths was relatively small in both groups.

Figure 12. 30-day all-cause mortality rate of Pseudomonas aeruginosa bacteraemia by age and sex, FY 2017 to 2018 versus FY 2022 to 2023

Figure 13. 30-day all-cause fatality rate of Pseudomonas aeruginosa bacteraemia by age and sex, FY 2017 to 2018 versus FY 2022 to 2023

MRSA bacteraemia

During FY 2022 to 2023, 787 MRSA bacteraemia cases were reported in England. Information on mortality was available for 98.5% (775) of these cases (Table S14 of the supplementary data set). There were 174 deaths within 30 days of an MRSA bacteraemia which was a mortality rate of 0.3 deaths per 100,000 population. The CFR was 22.5% of cases.

The CFR has been on a declining trend since the start of surveillance (FY 2007 to 2008), declining from 38.9% to 22.5%. Similarly, the mortality rate decreased from 2.6 to 0.3 deaths per 100,000 population between FY 2007 to 2008 and FY 2018 to 2019. While there was a small increase to 0.4 deaths per 100,000 in FY 2020 to 2021, at the start of the COVID-19 pandemic, the mortality rate in recent years has stabilised at 0.3.

Variation by onset of bacteraemia

The mortality rate of HO cases increased from 0.2 deaths per 100,000 bed-days (73 deaths) during FY 2019 to 2020 to 0.3 deaths per 100,000 bed-days (93 deaths) during FY 2020 to 2021 (Figure 14), but later subsequently returning 0.2 deaths per 100,000 bed-days during FY 2021 to 2022 (68 deaths) and has since remained stable at this level. The mortality rate of CO cases has remained at 0.2 per 100,000 population since FY 2018 to 2019 (Table S15 of the supplementary data set and Figure 14).

The CFR of HO cases decreased from 42.4% to 29.2% between FY 2007 to 2008 and FY 2019 to 2020, while for CO it decreased from 33.1% to 24.0% over the same period (Table S15 of the supplementary data set and Figure 14). Between FY 2019 to 2020 and FY 2020 to 2021, there was an increase in CFR of HO cases, from 29.2% to 34.3%, followed by a decrease in CFR to 29.6% during FY 2022 to 2023. The CFR of CO cases was stable between FY 2019 to 2020 and FY 2021 to 2022 and then sharply declined in FY 2022 to 2023 to 18.2%, its lowest level throughout the surveillance period.

Figure 14. 30-day all-cause mortality rate of hospital-onset and community-onset MRSA bacteraemia, FY 2007 to 2008 to FY 2022 to 2023

Figure 15. 30-day case fatality rate of MRSA bacteraemia by onset, FY 2007 to 2008 to FY 2022 to 2023

Variation by NHS commissioning region

Like the national trend, the majority of the regional mortality rates and the CFRs declined between FY 2007 to 2008 and FY 2022 to 2023. Of note, in the previous year, the South East region saw an increase in CFR, rising from 35.7% at the start of surveillance to 39.5% in FY 2021 to 2022. However, in FY 2022 to 2023, this figure decreased to 18.0%.

In FY 2022 to 2023, regional mortality rates ranged from 0.2 deaths per 100,000 population in the Midlands, South East and South West to 0.5 deaths per 100,000 population in the East of England (Table S16 of the supplementary data set). Over the same period, CFRs ranged from 14.6% in the South West to 37.6% in East of England. In the East of England region, between FY 2020 to 2021 and FY 2022 to 2023, there was an increase in mortality rate from 0.3 deaths per 100,000 population to 0.5 and CFR from 27.6% to 37.6%. In the South East and North West regions, the number of deaths, mortality rate and CFR were at their lowest since the inception of surveillance during FY 2022 to 2023.

Variation by age and sex

During FY 2022 to 2023, mortality rates and CFRs increased with age. There were only 2 exceptions to this trend; female cases aged 1 to 14 years had a higher CFR (11.8%) compared to those aged 15 to 44 years (5.5%). Similarly, female cases aged 45 to 64 years had a higher CFR (24.5%) compared to those aged 65 to 74 years (21.6%). Over the same period, the mortality rate was greater in males, while CFR differences varied by age group (Table S17 of the supplementary data set, Figure 16 and Figure 17).

Among male cases, the highest mortality rate was in those aged 85 years and over (7.6 deaths per 100,000 population) and those aged 75 to 84 years (2.5 deaths per 100,000 population), with CFRs being 51.9% and 41.1%, respectively, but markedly reduced to the rates seen in FY 2007 to 2008.

In female cases, the mortality rates were also higher in the oldest age groups, with 2.3 deaths per 100,000 population among those aged 85 years and over and 1.0 deaths per 100,000 population among those in aged 75 to 84 years. The CFRs of these 2 groups were 46.5% and 35.8%, respectively.

During FY 2022 to 2023, there were no deaths following MRSA bacteraemia in cases aged under one year.

Figure 16. 30-day all-cause mortality rate of MRSA bacteraemia by age and sex, FY 2007 to 2008 versus FY 2022 to 2023

Figure 17. 30-day all-cause case fatality rate of MRSA bacteraemia by age and sex, FY 2007 to 2008 versus FY 2022 to 2023

MSSA bacteraemia

During FY 2022 to 2023, 13,125 MSSA bacteraemia cases were reported in England. Information on mortality was available for 98.7% (12,950) of these cases (Table S18 of the supplementary data set). There were 2,837 deaths within 30 days of an MSSA bacteraemia which gave a mortality rate of 5.1 deaths per 100,000 population. The CFR was 21.9%.

There was an initial declining trend in CFR, starting from 21.5% during FY 2011 to 2012 to 19.1% during FY 2018 to 2019; this was followed by an increase to 23.7% during FY 2020 to 2021 and a subsequent decrease to 21.9% during FY 2022 to 2023. The overall trend of mortality rate increased from 3.3 deaths per 100,000 population to 5.1 in between FY 2011 to 2012 and FY 2022 to 2023 (the highest mortality rate for MSSA bacteraemia since the start of mandatory surveillance).

Variation by onset of bacteraemia

The mortality rate of HO cases increased from 2.1 deaths per 100,000 bed-days (724 deaths) during FY 2011 to 2012 to 2.8 deaths per 100,000 bed-days (978 deaths) during FY 2022 to 2023 (Figure 18), which is still higher than pre-pandemic levels. The mortality rate of CO cases was 3.3 deaths per 100,000 population during FY 2022 to 2023, increasing from the start of surveillance in FY 2011 to 2012, from a rate of 2.0 (Table S19 of the supplementary data set and Figure 18).

The CFR of HO cases decreased from 26.7% during FY 2011 to 2012 to 25.4% during FY 2022 to 2023, while for CO cases, it increased from 18.9% to 20.4% between FY 2012 to 2013 and FY 2022 to 2023, respectively (Table S19 of the supplementary data set and Figure 19). The CFR in HO and CO cases has shown a slow decline between FY 2012 to 2013 and FY 2019 to 2020; this coincides with the start of the COVID-19 pandemic. Subsequently, the CFRs peaked in FY 2020 to 2021, reaching 28.2% and 21.8% for HO and CO cases, respectively. Since then, these CFRs have shown a reduction, but remain above pre-pandemic levels.

Figure 18. 30-day all-cause mortality rate of hospital-onset and community-onset MSSA bacteraemia, FY 2011 to 2012 to FY 2022 to 2023

Figure 19. 30-day all-cause case fatality rate of MSSA bacteraemia by onset, FY 2011 to 2012 to FY 2022 to 2023

Variation by NHS commissioning region

During FY 2022 to 2023, regional mortality rates ranged from 3.3 deaths per 100,000 population in London to 6.6 deaths per 100,000 population in the North East and Yorkshire. Over the same period, CFRs ranged from 17.1% in London to 25.5% in the Midlands (Table S20 of the supplementary data set).

In FY 2022 to 2023, the Midlands, East of England, North East and Yorkshire, as well as the South West regions, recorded their highest mortality rates since the inception of surveillance in FY 2012 to 2013, with rates of 5.4, 4.3, 6.6, and 5.7 deaths per 100,000, respectively; these regions, with the exception of North East and Yorkshire, also observed an increase in CFR since FY 2021 to 2022. The mortality rates for London and North West regions reduced marginally by 0.1 deaths per 100,000. At the start of the COVID-19 pandemic, in FY 2020 to 2021, an increase in mortality rate was observed in all regions. All these regions subsequently decreased during FY 2021 to 2022. The CFR also fell in every region between FY 2020 to 2021 and FY 2021 to 2022.

Variation by age and sex

During FY 2022 to 2023, the mortality rate and CFR increased with age, except among children under the age of one. Mortality rates were greater in male cases while CFRs were close to equal in both sexes (Table S21 of the supplementary data set, Figure 20 and Figure 21).

Among male cases, the highest mortality rates were in the 85 years and over (92.3 deaths per 100,000 population) and the 75 to 84 years (33.6 deaths per 100,000 population) while CFRs of these age groups were 45.2% and 30.9%, respectively. The mortality rate in 85 years and over males has been increasing over time and was the highest since the start of surveillance during FY 2022 to 2023. In female cases, the mortality rates were also higher in older age groups, 45.8 deaths per 100,000 population (85 year and over years) and 17.5 deaths per 100,000 population (75 to 84 years). These equated to CFR of 48.3% and 32.8% of all cases in those respective age groups.

Among children under the age of one year, the mortality rate in male cases was 3.6 deaths per 100,000 population (5.9% of cases) compared to 2.0 deaths per 100,000 population (4.5% of cases) in female cases, although the numbers of deaths in this group are small and data should be analysed with caution.

Figure 20. 30-day all-cause mortality rate of MSSA bacteraemia by age and sex, FY 2011 to 2012 versus FY 2022 to 2023

Figure 21. 30-day all-cause case fatality rate of MSSA bacteraemia by age and sex, FY 2011 to 2012 versus FY 2022 to 2023

Clostridioides difficile infection

During FY 2022 to 2023, 15,583 CDI cases were reported in England. Information on mortality was available for 99.0% (15,421) of these cases (Table S22 of the supplementary data set). There were 2,131 deaths within 30 days of a CDI case, giving a mortality rate of 3.8 deaths per 100,000 population and CFR of 13.8%. This marks a gradual year-on-year increase in mortality rates since FY 2019 to 2020.

There was a declining trend in CFR from 26.3% during FY 2007 to 2008 to 13.5% during FY 2019 to 2020, after which the CFR increased to 14.9% during FY 2020 to 2021 before decreasing to 13.8% during FY 2022 to 2023. The overall trend of mortality rate decreased from 27.1 deaths per 100,000 population during FY 2007 to 2008 to its lowest level of 2.9 deaths per 100,000 population in FY 2018 to 2019 before increasing each financial year since to 3.8 deaths per 100,000 population in FY 2022 to 2023. The differing trend between FY 2019 to 2020 and FY 2020 to 2021 is likely a consequence of the COVID-19 pandemic.  

Variation by onset of infection

The mortality rate of HO cases decreased from 26.0 deaths per 100,000 bed-days (9,747 deaths) at the start of surveillance (FY 2007 to 2008) to its lowest level of 2.5 deaths per 100,000 in FY 2018 to 2019 before increasing subsequently to 3.7 deaths per 100,000 bed-days (1,298 deaths) during FY 2022 to 2023 (Table S23 of the supplementary data set and Figure 23). The same trend is observed with the mortality rate of CO cases, which decreased from 8.2 deaths per 100,000 population (4,226 deaths) at the start of surveillance to its lowest level of 1.3 deaths per 100,000 in FY 2018 to 2019 before increasing subsequently to 1.5 deaths per 100,000 population (833 deaths) during FY 2022 to 2023 (Figure 22).

The CFR of HO cases decreased from 30.2% to 20.2% between FY 2007 to 2008 and FY 2022 to 2023. The CFR of CO cases also decreased from 20.2% to 9.3% between FY 2007 to 2008 and FY 2022 to 2023 (Table S23 of the supplementary data set and Figure 24). Though the CFR in HO and CO showed a slow decrease between FY 2007 to 2008 and FY 2021 to 2022, the decrease was only constant between FY 2007 to 2008 and FY 2019 to 2020, which coincides with the start of the COVID-19 pandemic. Between FY 2020 to 2021 and FY 2022 to 2023,  a small decline was observed in the CFR for HO and CO cases in FY 2021 to 2022. The CFR for both continues to remain at a similar level in FY 2022 to 2023 (20.0% vs 20.2%).

Variation by prior healthcare exposure

The mortality rate of hospital-onset healthcare-associated (HOHA) cases increased from 3.1 deaths per 100,000 bed days during FY 2019 to 2020 to 4.0 deaths per 100,000 bed days (1,420 deaths), the highest seen since the start of using these prior healthcare exposure definitions, during FY 2022 to 2023. The mortality rate of community-onset community-associated (COCA) cases has been increasing between FY 2018 to 2019 and FY 2022 to 2023, from 0.4 deaths per 100,000 population to 0.5 deaths per 100,000 population. The community-onset healthcare-associated (COHA) mortality rate increased from 0.4 to 0.5 deaths per 100,000 day admissions and bed days from FY 2017 to 2018 to FY 2019 to 2020 and has remained at this level since (Table S24 of the supplementary data set).

Figure 22. 30-day all-cause mortality rate of hospital-onset and community-onset CDI, FY 2007 to 2008 to FY 2022 to 2023

Figure 23. 30-day all-cause case fatality rate of CDI by onset, FY 2007 to 2008 to FY 2022 to 2023

Variation by NHS commissioning region

During FY 2022 to 2023, regional mortality rates ranged from 2.3 deaths per 100,000 population in London to 5.3 deaths per 100,000 population in the North West. Over the same period, CFRs ranged from 12.1% in London to 15.5% in the North East (Table S25 of the supplementary data set).

Variation by age and sex

CDI surveillance only covers cases over 2 years of age. The CFR following CDI infections increased with age. Mortality rate and CFR increased with age and was greater in male cases compared to female cases (Table S26 of the supplementary data set, Figure 24 and Figure 25).

Among male cases, the highest mortality rates were in the 85 year and older age group (70.2 deaths per 100,000 population) and the 75 to 84 years (23.5 deaths per 100,000 population), with a corresponding CFR of 27.0% and 17.8%, respectively, in FY 2022 to 2023.

In female cases, the mortality rates were also higher in older age groups, 50.9 deaths per 100,000 population (85 years and over age group) and 17.0 deaths per 100,000 population (75 to 84 years) during FY 2022 to 2023. These equated to CFRs of 19.7% and 13.0% of all cases in those respective age groups.

Figure 24. 30-day all-cause mortality rate of CDI by age and sex, FY 2007 to 2008 versus FY 2022 to 2023

Figure 25. 30-day all-cause case fatality rate of CDI by age and sex, FY 2007 to 2008 versus FY 2022 to 2023

Discussion

Trends in incidence and deaths associated with all infections covered in this report were impacted by the COVID-19 pandemic. In many cases trends have now returned to pre-pandemic levels. After an initial decline in incidence of bacteraemia and CDI observed from FY 2020 to 2021 to FY 2021 to 2022, the number of infections has since increased in the latest financial year, 2022 to 2023 as reported in the annual epidemiological commentary. This is coupled with an increase in the number of deaths within 30 days of being diagnosed with bacteraemia or CDI, from 13,574 deaths in the previous financial year, to 14,621 deaths in FY 2022 to 2023.

The previous year, FY 2021 to 2022 saw a decline in mortality rate and CFR, compared to the large spike observed at the start of the COVID-19 pandemic (FY 2020 to 2021). FY 2022 to 2023 saw an increase in both mortality rate and CFR compared to the previous year, where CFR increased from 17.1% to 17.6% and mortality rate increased from 25.3 to 26.2 deaths per 100,000 population. However, CFR remains lower than the FY 2020 to 2021 level of 18.6%, and as well as the start of surveillance (FY 2007 to 2008) when it was 27.0%. In contrast, the overall mortality rate which reached its lowest level in FY 2018 to 2019 in the recent period (FY 2017 to 2018 to FY 2022 to 2023) at 22.8 deaths per 100,000 population; it is now the highest rate observed since FY 2008 to 2009 and has been gradually increasing since then.

Differing trends in the most recent financial years are likely in some part a consequence of the COVID-19 pandemic. Fewer infections were observed than expected across many of the bacteraemia and CDI initially, in FY 2020 to 2021. However, increases were observed in the mortality rate of hospital-onset cases during FY 2020 to 2021, compared with FY 2021 to 2022 and FY 2019 to 2020. This may be due to a decrease in bed-days observed during FY 2020 to 2021, with a reduction in hospital activity, as well as reduced mixing due to lockdown events (coinciding with the COVID-19 pandemic). The effect of specific factors contributing to the changes in mortality rate has yet to be discerned and are under investigation. The increase in CFR in FY 2020 to 2021 may reflect poor outcomes in patients with both a bacteraemia or CDI and COVID-19, or a skew toward bacteraemia cases with a respiratory source during this period reported in a National Center for Biotechnology Information study.

During the COVID-19 pandemic, there was an increase in CFR in E. coli bacteraemia cases (14.3% to 16.0%) between FY 2019 to 2020 and FY 2020 to 2021. However, there was a decrease in mortality rate (11.0 to 10.4 deaths per 100,000 population) over the same period. The CFR of E. coli bacteraemia (15.9%) was relatively small compared with those for MRSA and P. aeruginosa bacteraemia in FY 2022 to 2023. However, its higher incidence of infection, and deaths following infection (mortality rate: 10.9 deaths per 100,000 population) compared with MRSA (mortality rate: 0.3 deaths per 100,000 population) and P. aeruginosa bacteraemia (mortality rate: 2.0 deaths per 100,000 population) highlights the public health burden of this infection.

The continued increase in mortality rates following E. coli bacteraemia is of particular concern. During FY 2022 to 2023, there were 6,087 deaths within 30 days of E. coli bacteraemia, its highest level since the start of surveillance, and in the context of lower infections compared to pre-pandemic. This is approximately 5 times the number of deaths following MRSA bacteraemia at the start of mandatory surveillance (FY 2007 to 2008, 1,354) when MRSA bacteraemia cases were at its highest levels. Of particular concern, there has been a gradual rise in MSSA bacteraemia mortality rate in recent years, coinciding with the increase in incidence. This increase is predominantly driven by community-onset deaths and reached its peak in FY 2022 to 2023, marking the highest level observed since surveillance began.

Until recently, both CDI and MRSA bacteraemia showed a consistent decline in mortality rates and CFRs, reflecting the change in their epidemiology over the years. The incidence of these infections had also been on the decline, shifting from primarily being hospital infections to more frequently originating in the community. Given that hospital-onset (a proxy for healthcare-acquired) cases typically have higher mortality and morbidity compared to community-onset cases, the reduction in hospital-acquired infections was likely contributing to an overall decrease in CFRs, as was observed in MRSA bacteraemia cases. However, since FY 2020 to 2021, there has been a noticeable divergence in these trends, with CDI now showing a gradual but concerning year-on-year increase in mortality rate, coupled also with increasing incidence, notably in hospital-onset cases. In contrast, MRSA bacteraemia has maintained a relatively stable mortality rate since FY 2018 to 2019, with a small increase observed at the start of the COVID-19 pandemic (Figure 14; Table S15 of the supplementary data set).

Limitations

The analyses presented here are based on infections reported to UKHSA that could be linked to the NHS Spine to obtain mortality information. While most of infection reports had complete NHS numbers (required for linkage), for some reports the NHS Spine was not able to return patient information. This was due to reasons such as the NHS number and date of birth not matching a record on the NHS Spine. Thus, there may be bias in the records with available mortality information, which may over- or under-estimate the number of deaths and associated CFRs, if the records without mortality information were for patients with a different likelihood of death. However, this effect on reported outcomes is likely to be low, since the linkage had a high degree of completeness, at around 97.5% of all cases.

Crude CFRs are presented and as such have not been adjusted for potential confounders such as age, sex or co-morbidities, which may affect comparisons over time, between regions and onset setting.

Finally, while analysis of 30-day all-cause mortality estimates the risk of death following an infection within a fixed time frame it does not provide insight into attributable mortality. However, it is difficult to ascertain attributable mortality in practice, due to clinical and diagnostic uncertainty encountered when trying to determine the exact cause of death in patients, particularly in those with multiple co-morbidities.

The ONS has historically published statistics on deaths involving MRSA and C. difficile. These statistics are not comparable with those presented here for the reasons highlighted in the methods.

Background information

Our statistical practice is regulated by the Office for Statistics Regulation (OSR). OSR sets the standards of trustworthiness, quality and value in the Code of Practice for Statistics that all producers of official statistics should adhere to. You are welcome to contact us directly by emailing mandatory.surveillance@ukhsa.gov.uk with any comments about how we meet these standards. Alternatively, you can contact OSR by emailing regulation@statistics.gov.uk or via the OSR website. 

The UKHSA is committed to ensuring that these statistics comply with the Code of Practice for Statistics. This means users can have confidence in the people who produce UKHSA statistics because our statistics are robust, reliable and accurate. Our statistics are regularly reviewed to ensure they support the needs of society for information. The suite of HCAI Official Statistics were last formally reviewed internally through spring and summer 2023. Following this review, an implementation plan was developed to continue to improve the trustworthiness, quality and value of the statistics. Actions implemented so far include:    

• improving completeness of Trust-level data following work carried out with NHS England
• more accurate data processing and quality checks – most manual analysis and data quality checks have been automated to reduce human error
• comprehensive documentation in place for all reproducible analytical pipelines
• improvements to spreadsheets and data visualisations to ensure that they are fully accessible

UK Health Security Agency (UKHSA) has undertaken mandatory surveillance of key healthcare-associated infections (HCAI) in England since 2001, when NHS acute trusts were mandated to report aggregate counts of S. aureus bacteraemia and the number that were MRSA. Case-level reporting was introduced for MRSA in 2005, and for CDI in patients, aged at least 2 years, since April 2007. The mandatory surveillance programme was expanded to include MSSA and E. coli bacteraemia in January and July 2011, respectively. In April 2017, Klebsiella spp. and P. aeruginosa bacteraemia were also added to the surveillance programme.

Over time, the dominance of HO MRSA, MSSA, Gram-negative bacteraemia and CDI has declined, with a corresponding increase in the proportion of CO cases. Since the composition of the patient population can vary in each setting, this publication reports mortality outcomes by onset of infection, and by prior healthcare exposure for CDI. Due to the impact of HCAI on patients’ morbidity and mortality, monitoring trends in mortality is an important part of HCAI surveillance.

This report presents an analysis of 30-day all-cause mortality among MRSA, MSSA, E. coli, Klebsiella spp. and P. aeruginosa bacteraemia, and CDI patients. A separate report presents an analysis of the incidence of all reported cases of these same infections.

Methods

Infection reports

Data on MRSA, MSSA, E. coli, Klebsiella spp. and P. aeruginosa bacteraemia, and CDI were extracted on 24 April 2022 from the HCAI Data Capture System (DCS). This data covers the period from the start of surveillance for each data collection (April 2007 for MRSA BSI and CDI; April 2011 for MSSA BSI; April 2012 for E. coli BSI; April 2017 for Klebsiella spp. and P. aeruginosa BSI) to March 2023, the disparate time periods reflect the first full financial year available for each of the infections. Reports of CDI from patients aged under 2 years at the time of specimen collection were excluded from all analyses because this data is not subject to mandatory surveillance, as carriage rates of C. difficile are high with little evidence for disease in this age group.

Mortality data

Mortality data were obtained by linking the HCAI DCS extract with the NHS spine, a central repository of patient demographic and medical information managed by the Health and Social Care Information Centre. Records were traced using the NHS number and date of birth (DOB). Only records that match on both the NHS number and the DOB can be successfully traced and have the potential for fatality information to be returned. These are referred to as ‘linked or traced reports’ in this document and the accompanying datasheet. Within the HCAI DCS, NHS number and DOB are mandatory fields for entering and saving a case onto the surveillance system. Users can enter ‘9’s in place of a valid NHS number if the NHS number is unknown, while 01/01/1900 is used for DOB if it is unknown. Only traced reports are considered when calculating CFR.

For infection reports with a death reported in the NHS Spine, the time in days between specimen date and date of death was calculated to identify whether it was within a 30-day window. Bacteraemia reports with a date of death 2 or more days prior to the specimen date were excluded from the analysis. In publications prior to September 2018, CDI cases with dates of death 3 or more days before the sample data were excluded. However, since then such cases have been included and are considered a 30-day all-cause death. On the HCAI DCS, MRSA, MSSA, E. coli, Klebsiella spp. and P. aeruginosa bacteraemia episode lengths are 14 days, and CDI is 28 days, therefore it is possible to have multiple cases within 30 days of a death. Where multiple records from the data collection (bacteraemia or CDI) had the same NHS number and date of birth within the 30-day mortality window, only the record with the specimen date closest to the date of death was used to calculate 30 day all cause CFR. This was done to prevent estimate bias by overestimating of the numbers of deaths. This deduplication algorithm was applied to both the 30-day mortality, traced and total number of reports to prevent an inflated count of deaths and reports.

Records between financial years 2007 to 2008 and 2014 to 2015 were originally traced on 4 July 2015. A secondary trace was conducted on all records between financial years 2013 to 2014 and 2016 to 2017 on 3 July 2017. Records after financial year 2016 to 2017 were traced in the same financial year they were published: for the latest data, this occurred on 22 June 2023.

Caveats

The number of infections and deaths presented here may differ from those in earlier publications due to late reports, inclusion of new reports since previous publications, or mortality re-tracing.

Data in this report are presented by financial year based on the date of sampling of the first positive specimen rather than the date of death. It is therefore possible that a death occurred in a different financial year from what is presented in this report. When the date of sampling was not known, the date when the sample was received in the laboratory was used as a proxy.

De-duplication algorithm

This report uses the same base data as UKHSA’s 2022 to 2023 Annual HCAI Epidemiological Commentary. Unlike the annual report, in this publication counts of infections and deaths within 30 days of specimen collection have been deduplicated by infection to a patient level. If a patient was positive for multiple types of infection within 30 days of their death, they will be counted for each infection. This ensures that a patient’s mortality outcome is reflected for each infection.

Blood (faecal for CDI) sample with the earliest specimen date before the patient’s date of death was considered the index sample. However, if there was a bacteraemia positive post-mortem sample within one day after a patient’s date of death, and no other case was reported within 30-day prior to the patient’s date of death, that post-mortem sample is taken as the index sample and considered a 30-day all-cause death. This short period of allowance is included to account for the possibility of late reports and data entry errors. Post-mortem bacteraemia samples after this period of allowance are excluded and not included in either the denominator (linked cases) or numerator (30-day all-cause deaths) of CFR analyses.

In contrast, CDI positive post-mortem samples are included in CFR where applicable since they are subject to mandatory surveillance. For the purpose of this report, patients with a post-mortem CDI faecal sample are assumed to have died to on the same date as their most recent sample. If no other CDI positive sample was reported within 30 days prior to the patient’s date of death, these CDI positive post-mortem samples are taken as index cases and considered 30-day all-cause deaths

For bacteraemia and CDI samples which could be linked to fatality records, the most recent sample was taken as an index sample. Bacteraemia and CDI positive samples with specimen dates before index samples but within a 30-day window period prior to the patient’s date of death are excluded as duplicates.

Deduplication is done at a data collection-level. This means that each data collection will have its own index sample if a patient tests positive for multiple infections covered in this report. Additionally, only duplicates of the same type of infection are excluded. For example, if a patient tests positive for MRSA, E. coli and CDI samples within 30-days of each other, they will be included in CFR calculation 3 times, once for each data collection.

Calculation of case fatality rates

Case fatality rates (CFR) indicate the risk of death per case of a particular infection. They were calculated as:

CFR equals 100 multiplied by (number of deaths from any cause occurring within 30 days of sampling date) divided by (number of cases)

Thus, if the ratio of deaths to cases remains constant over time, so will the CFR, even if there has been an overall increase or decrease in both the number of deaths and cases. By contrast, if the number of deaths increases but the number of cases remains constant, or if the number of deaths remains constant but the number of cases decreases, the CFR will increase. Thus, the CFR facilitates comparison between clinical outcomes of diseases with differing incidence.

Estimation of number of 30-day all-cause deaths

An estimate of the number of deaths that might be observed in each period if all infection reports could have been linked to mortality records was calculated.

Number of 30-day all-cause deaths equals (number of de-duplicated infection reports submitted to the HCAI DCS for a given financial year) divided by (30-day CFR expressed as a proportion)

This is rounded to the nearest whole number. Care should be taken with interpretation of this metric, as it assumes the risk of death for those cases that could and could not be linked are the same.

Calculation of mortality rates

Mortality rate is a measure of deaths in the population at risk. This contrasts with the CFR, which shows the percentage of people with an infection who die within 30 days. The Mortality rate for each infection is calculated as:

Mortality rate equals (number of deaths from any cause occurring within 30 days of sampling date) divided by (population estimate)

The population estimate is based on England’s mid-year estimates by ONS when calculating the Mortality rate among CO infection. For HO cases, the population estimate used were NHS overnight admissions. However, for COHA cases, NHS overnight and day admissions were used.

Comparability with previous ONS publications on mortality

The Office for National Statistics (ONS) previously published data on deaths in England involving MRSA and C. difficile. The ONS data on MRSA bacteraemia and CDI are not comparable to the data published here for several methodological reasons:

Pathogens

UKHSA outputs cover deaths relating to MRSA, MSSA, E. coli bacteraemia and C. difficile infection whereas ONS outputs cover deaths relating to MRSA bacteraemia and C. difficile, only.

Mortality data source and definition

UKHSA uses NHS spine reports of death from all causes, within 30 days of the date of a positive specimen, whereas ONS uses death certificates, only including deaths for which the pathogen was explicitly listed as a cause of death. All-cause mortality is a common epidemiological convention; while it is not known if the deaths were attributable to the HCAIs, the use of all-cause mortality provides a consistent methodology to determine the temporal trends and reduces the subjectivity of cause of death or changes in priorities for death certification.

Geography

UKHSA fatality outputs cover England only whereas ONS outputs cover England and Wales.

Time period covered

UKHSA outputs are timed by financial year whereas ONS outputs use the calendar year.

Denominator

UKHSA outputs use all traced reports of MRSA, MSSA, E. coli, P. aeruginosa and Klebsiella spp. bacteraemia or CDI in the given time period as the denominator whereas ONS use all deaths in the given time period and population in the given time period (2 different denominators used).

Revisions to data included are covered by a data-specific revisions and correction policy.

Citations

Citation to UK Health Security Agency (UKHSA), healthcare associated infections (HCAI) and antimicrobial resistance (AMR) division is required, if this data is used for publication elsewhere, using the content above.

Citation: UK Health Security Agency. MRSA, MSSA, Gram-negative bacteraemia and CDI: 30-day all-cause mortality, London: UK Health Security Agency, March 2023.