Weekly all-cause mortality surveillance (week 8 report, up to week 4 2024 data)
Updated 25 April 2024
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This report includes details of the weeks in which all-cause observed deaths were higher than an expected 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 and requires further investigation.
This report covers the UK. Analysis is based on UK data, stratified by age and region in England, and all deaths combined in Northern Ireland, Scotland and Wales.
Main points
In week 4 of 2024, all-cause mortality by week of death occurence was statistically significantly above the EuroMOMO algorithm baseline for:
- those aged 5 to 14 years in England
- all ages combined in Northern Ireland
- all ages combined in Scotland
No signal of high mortality above the baseline was seen in England using all ages combined, or for those aged under 5 years, aged 15 to 64 years, and aged 65 years and over, or in any region.
No signal of high mortality above the baseline was seen in 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 signal.
Figure 1 shows the output for England using all ages combined and includes indication of the main circulating influenza subtypes and recent SARS-CoV-2 periods which align with high mortality signals.
In summer, heat is also a common reason for signals. In the most recent summer in England, heat-health alerts were issued for 9 to 13 June 2023 (weeks 23 to 24) and for 3 to 12 September 2023 (mainly week 36).
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 week 4 of 2024, nor in any region. By age group, a statistically significant mortality signal was seen in those aged 5 to 14 years only. Weeks since week 20 of 2023 where a signal was identified are shown in Tables 1 and 2.
In the devolved administrations, data are 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 Northern Ireland and Scotland in week 4 using EuroMOMO applied by week of death occurrence (Table 2). No signal of high all-cause mortality for all ages was observed in 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, 2017 to week 4 of 2024
Note: the recent weeks’ data are estimates which may be subject to registration delay corrections and therefore should be interpreted with caution. These estimates may differ in future reports as more deaths are registered.
Table 1. Weeks with a high mortality signal by age group, England [note 1]
| Age group (years) | Signal in week 4 2024 | Weeks with a signal since week 20 of 2023 |
|---|---|---|
| Under 5 | No | Weeks 41, 49 to 50 |
| 5 to 14 | Yes | Week 4 |
| 15 to 64 | No | None |
| 65 and over | No | None |
Table 2. Weeks with a high mortality signal by UK country, for all ages [note 1]
| Country | Signal in week 4 2024 | Weeks with a signal since week 20 of 2023 |
|---|---|---|
| England | No | None |
| Wales | No | None |
| Northern Ireland | Yes | Weeks 44, 4 |
| Scotland | Yes | Weeks 51 to 1, 3 to 4 |
[note 1]: Signal is defined as being above the 2 z-score threshold by the EuroMOMO algorithm.
Data interpretation and further 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 expected higher level 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.
The baseline shown in Figure 1 comes from the standardised EuroMOMO algorithm which aims to give expected mortality in the absence of an acute event that may increase mortality, such as 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.
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 is defined as a statistically significant (above the upper 2 z-score threshold) number of deaths reported over that expected for a given point in the year, allowing 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).
Other assessments of all-cause mortality
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 z-score data provided to the hub by each country. The hub produce a European wide aggregated output and results from 28 countries for comparison of signals across Europe using a standard method.
The provisional number of weekly deaths registered in England and Wales is published online by the Office for National Statistics (ONS). Estimates of excess mortality are also published by ONS using a method that uses recent mortality trends by week, age, region and sex.
The Office for Health Improvement and Disparities (OHID) also produce the excess mortality in England and English regions report, which uses ONS death registration data by week of registration and includes breakdowns by cause of death and place 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.
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.