This report includes details of the weeks in which observed deaths from all causes were higher than a threshold, which is calculated using a European-wide algorithm called EuroMOMO. It can be used to identify weeks when factors such as infectious disease activity or extreme temperature may have caused higher mortality rates than expected.

This report covers the UK. Analysis is stratified by age and region in England, and by all deaths combined in Northern Ireland, Scotland and Wales.

Main points

The main messages of this report are:

• in week 52 of 2024, no signal of high mortality above the baseline was seen in England using all ages combined

• no signal of high mortality above the baseline was seen in England in those aged under 5 years, aged 5 to 14 years, aged 15 to 64 years, and aged 65 years and over

• a signal of high mortality above the baseline was seen in England in the North East using all ages combined

• a signal of high mortality above the baseline was seen in Scotland using all ages combined

• no signal of high mortality above the baseline was seen in Northern Ireland or Wales using all ages combined

Identifying signals of high all-cause mortality in subpopulations, UK

This analysis uses all-cause deaths by week of death occurrence with a correction for delays from death to registration using the standardised EuroMOMO algorithm. The algorithm used also produces a baseline estimate and z-score thresholds, with results above 2 z-scores regarded as a high mortality signal.

Figure 1 shows the number of deaths for England using all ages combined and demonstrates the main circulating influenza subtypes and recent SARS-CoV-2 periods which align with high death rates. Last season was a mixed A/H1N1pdm09 and A/H3N2 season. The figure includes death estimates to week 3 of 2025 but the most recent 3 weeks (in the grey area) have very high uncertainty and are not assessed in this report for the purpose of identifying high mortality signals.

In England, aggregated death registrations are provided to UK Health Security Agency (UKHSA) by the General Register Office (GRO). Mortality by week of death occurrence above the 2 z-score threshold was not seen overall in the week ending 29 December 2024 (week 52). It was not seen in any age group or region, except the North East. The weeks where a high mortality signal was identified (since week 20 of 2024) are shown in tables 1 to 3.

In the devolved administrations, data is based on GRO data for Wales, National Records of Scotland (NRS) data for Scotland, and Northern Ireland Statistics and Research Agency (NISRA) data for Northern Ireland. A signal of high all-cause mortality above the baseline for all ages was observed in Scotland in the week ending 29 December 2024 (week 52) applied by week of death occurrence (Table 3).

No signal of high all-cause mortality above the baseline for all ages was observed in Northen Ireland and Wales.

Note that the data is provisional because of the time delay in registration, so numbers may vary from week to week. Data presented in this week’s report supersedes data presented in reports from previous weeks.

Figure 1. Weekly observed and expected number of all-cause deaths in all ages, with the dominant circulating respiratory virus, England, week 40 2019 to week 52 of 2024 (solid black line), also showing to week 3 of 2025 (dotted black line)

Note: The most recent weeks’ estimates can have large changes in future reports, particularly those in the grey area. This is because large corrections are applied to allow for delays to registration. It is important to note that corrections are also based on historic delays which may not reflect more recent delays. In recent months, the corrected deaths in the most recent weeks have been underestimating the final numbers as indicated on the graph by the drop in the grey area.

Table 1. Weeks with a high mortality signal by age group, England [note 1]

Age group (years)	Signal in week 52 2024?	Weeks with a signal since week 20 2024
Under 5	No	None
5 to 14	No	None
15 to 64	No	None
65 and over	No	None

Note 1: ‘signal’ is defined as being above the 2 z-score threshold by the EuroMOMO algorithm. A signal for a given week may change in future reports as the estimate of deaths occurring in that week is updated.

Table 2. Weeks with a high mortality signal by region, England for all ages [note 1]

Region	Signal in week 52 2024?	Weeks with a signal since week 20 2024
East Midlands	No	None
East of England	No	None
London	No	None
North East	Yes	Week 52
North West	No	None
South East	No	None
South West	No	None
West Midlands	No	None
Yorkshire and Humber	No	None

Note 1: ‘signal’ is defined as being above the 2 z-score threshold by the EuroMOMO algorithm. A signal for a given week may change in future reports as the estimate of deaths occurring in that week is updated.

Table 3. Weeks with a high mortality signal by UK country, for all ages [note 1]

Country	Signal in week 52 2024?	Weeks with a signal since week 20 2024
England	No	None
Wales	No	Weeks 31, 51
Northern Ireland	No	None
Scotland	Yes	Week 52

Note 1: ‘signal’ is defined as being above the 2 z-score threshold by the EuroMOMO algorithm. A signal for a given week may change in future reports as the estimate of deaths occurring in that week is updated.

Glossary

Z-score

A z-score is a statistical measure of how many standard deviations above the baseline threshold the number of deaths was. For example, a z-score of 2 means that the number of deaths was 2 standard deviations above the baseline threshold. Chance signals using a 2 z-score threshold are expected about 2.5% of the time.

Data sources and methodology

The baseline shown in Figure 1 comes from the standardised EuroMOMO algorithm which aims to show expected mortality in the absence of a serious event that may increase mortality. Such events include when influenza circulation is high, or extreme temperatures. The algorithm uses 5 baseline years and incorporates a trend and seasonality. Note that the COVID-19 pandemic period from March 2020 to March 2022 is excluded from the baseline calculation. The algorithm also corrects the recent observed deaths in each week to allow for delays to registration based on historic delays. For example, if historically 90% of deaths in a given age group or region are estimated to have been registered within 4 weeks of registration, allowing for bank holidays and the observed number of deaths to date, then the corrected estimate from 4 weeks ago is obtained by dividing the observed deaths by 0.9.

This weekly mortality surveillance aims to provide timely detection and reporting of signals that mortality is above baseline seasonal levels. These signals support public health risk assessment, which may include investigation of possible causes.

High mortality for a given week is reported when the number of deaths occurring is above the expected number of deaths for that week of the year by an amount that exceeds the upper 2 z-score threshold. This definition allows for weekly variation in the number of deaths.

The aim is not to assess general mortality trends or estimate the deaths attributable to different factors. Attribution of above-baseline mortality is done using more detailed analyses, incorporating information on possible causes such as temperature and influenza rates (for example, annual influenza surveillance and heat mortality monitoring reports).

Background information

Seasonal variation in mortality is seen each year, with a higher number of deaths in winter months compared with the summer. Additionally, peaks of mortality above this threshold typically occur in winter, most commonly the result of factors such as cold snaps and increased circulation of respiratory viruses, in particular influenza. In summer, peaks can arise because of heatwaves.

Related statistics

A graphical z-score-only version of the EuroMOMO output is available for England, Scotland, Wales, Northern Ireland and across Europe from the EuroMOMO hub using data provided to the hub by each country. The hub produces a Europe-wide aggregated output and results from 28 countries for comparison of signals across Europe using a standard method.

Other assessments of all-cause mortality include the provisional number of weekly deaths registered in England and Wales, which is published online by the Office for National Statistics (ONS). Estimates of excess mortality are also published by the ONS using a method that compares deaths by week of registration to a baseline calculated using multi-year trends in the mortality rate, stratified by week, age, region and sex.

The Office for Health Improvement and Disparities (OHID) also produces the Excess mortality within England report, which provides estimates of expected deaths by month of registration for population subgroups and by cause of death.

The different methods used in the UK for mortality assessment, and their varied purposes, are discussed in more detail in Measuring excess mortality: a guide to the main reports.

Further information and contact details

Feedback and contact information

To provide feedback on this report, please email immunisation.resp_viruses@ukhsa.gov.uk

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