Mpox (monkeypox) outbreak: epidemiological overview, 23 August 2023 (interim update)
Updated 12 December 2024
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This epidemiological overview provides an interim update to the number of confirmed and highly probable mpox cases in England, Northern Ireland, Scotland and Wales. This update, originally published on 23 August, is in addition to the usual monthly report.
On 6 September, revisions were made to correct 2 errors in the number of cases presented in Figure 1 and the UK totals in Table 1.
Mpox is a zoonotic infection, caused by the monkeypox virus, that occurs mostly in West and Central Africa. Prior to 2022, cases diagnosed in the UK had been either imported from countries where mpox is endemic or contacts with documented epidemiological links to imported cases. Between 2018 and 2021, there had been 7 cases of mpox in the UK. Of these, 4 were imported, 2 were cases in household contacts, and one was a case in a health care worker involved in the care of an imported case. There was no documented community transmission in previous outbreaks.
The UK strategy for mpox control is to eliminate person-to-person transmission of mpox in the UK. Disease elimination is defined by the World Health Organization (WHO) European Region as the absence of indigenously acquired cases for a period of at least 3 months, in the presence of a well-performing surveillance system.
Current epidemiological situation up to 21 August 2023
Detection of cases of mpox infection, acquired within the UK, were confirmed in England from 6 May 2022. The outbreak has mainly been in gay, bisexual, and other men who have sex with men without documented history of travel to endemic countries.
Suspected mpox samples that are positive using a mpox polymerase chain reaction (PCR) test are classified as confirmed cases. Samples which are positive using an orthopox PCR test are classified as highly probable cases. Orthopox is the group of viruses which includes mpox. The counts below combine both of these categories.
Up to 31 December 2022 there were 3,732 confirmed and highly probable mpox cases reported in the UK. Of these, 3,553 were in England, 34 were in Northern Ireland, 97 were in Scotland and 48 were in Wales.
In 2023 (up to 21 August 2023) there has been a total of 46 cases of mpox reported in the UK. Of these, 44 were in England (21 cases were presumed to have acquired mpox in the UK, 19 were acquired outside the UK and 4 awaiting classification), one was in Scotland (an imported case acquired outside the UK) and one was in Wales (an imported case acquired outside the UK).
Figure 1 shows the weekly number of cases in 2023, where there were between 0 and 5 cases a week, compared to the weekly high of 350 cases in July 2022. Most recent cases, among those seen from April 2023 onwards, have been focussed in London, with 2 cases reported from the North West of England (Greater Manchester).
Figure 1. Number of confirmed and highly probable mpox cases in England, by week in 2023
Table 1. Number of confirmed and highly probable mpox cases by UK nation of residence, 6 May 2022 to 21 August 2023*
| UK nation | Cases reported in 2022 ** | Cases presumed acquired in the UK in 2023 | Cases presumed acquired outside the UK (imported) in 2023 | Cases awaiting classification in 2023 | Total (2022 and 2023) |
|---|---|---|---|---|---|
| England | 3,553 | 21 | 19 | 4 | 3,597 |
| Northern Ireland | 34 | 0 | 0 | 0 | 34 |
| Scotland | 97 | 0 | 1 | 0 | 98 |
| Wales | 48 | 0 | 1 | 0 | 49 |
| Total | 3,732 | 21 | 21 | 4 | 3,778 |
*Based on data extracted on 21 August 2023.
**Figures for 2022 start from 6 May 2022 and combine UK acquired and imported cases.
Data sources
Mpox surveillance data in England is based on mpox and orthopox virus test results from the Rare and Imported Pathogens Laboratory (RIPL), which is the UK Health Security Agency (UKHSA) mpox reference laboratory, and other UK laboratories with mpox and orthopox testing.
Counts of confirmed cases in Wales, Northern Ireland, and Scotland are submitted to UKHSA by Public Health Wales, Public Health Agency Northern Ireland, and Public Health Scotland respectively.
Information about this publication
These figures are used for official reporting of mpox confirmed case counts in the UK.
England counts may differ from those published in the Notifications of infectious diseases (NOIDs) causative agents weekly report. This is due to differences in timings of when the data is compiled, and differences in processing of duplicate data (for example, if a person has tested more than once but insufficient information is provided to identify them).
As mpox continues to be a notifiable infection, please refer to UKHSA’s NOIDs reports for weekly updates (but not cumulative totals) on laboratory-notified mpox cases in England.
While data cleaning is carried out routinely, corrections can be applied between reports, such as updates to patient information and the removal of quality assurance samples from laboratory surveillance systems.
Additional resources
Mpox outbreak: technical briefings
Mpox contact tracing guidance: classification of contacts and advice for vaccination and follow-up