Research and analysis
Outbreaks under monitoring: week 39 (week ending 28 September 2025)
Updated 2 October 2025
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| Disease or pathogen | Chikungunya |
|---|---|
| Location | France |
| Status | Situation update |
| Reporting date | 24 September 2025 |
| Summary | Between 1 May and 22 September 2025, 570 locally acquired cases of chikungunya were recorded in mainland France. This is an increase of 91 cases since the last report on 17 September 2025. There has been a continued decrease in newly reported cases following a peak on 27 August 2025. A majority of imported cases were associated with travel to Réunion (742 cases). In the United Kingdom (UK), an increase in travel-associated chikungunya cases has been reported in 2025. Most cases reported travel to Sri Lanka, India and Mauritius. No locally acquired cases of chikungunya have ever been reported in the UK. |
| Further information |
Chikungunya: transmission, epidemiology and guidance Chikungunya: epidemiology in England, Wales and Northern Ireland NaTHNaC country information page: France |
| Disease or pathogen | Ebola virus disease |
|---|---|
| Location | Democratic Republic of the Congo (DRC) |
| Status | Situation update |
| Reporting date | 4 to 24 September 2025 |
| Summary | On 4 September 2025, the DRC’s Ministry of Health reported an outbreak [in French] of Ebola virus disease (EVD) in Bulape health zone, Kasai Province. Media sources [in French] have since reported that 64 EVD cases (53 confirmed and 11 probable) and 42 deaths (31 confirmed and 11 probable) have been registered, as of 26 September 2025. On 24 September 2025, UNICEF reported that 45,000 doses of the Ebola vaccine are being transported to Kasai Province as part of response activities to the outbreak. This is in addition to a consignment of 20,000 vaccine doses already in Kasai Province being used to vaccinate healthcare workers and those individuals most at risk. On 22 September 2025, media reported that school activities in Mweka territory [in French] have resumed after being suspended in response to the EVD outbreak. The media report further stated that handwashing stations have been installed and there will be regular health briefings and establishment of a data collection centre to monitor the situation in schools. The World Health Organization (WHO) assesses the public health risk of this outbreak as high at the national level, moderate at the regional level and low at the global level. Imported cases of Ebola disease are very rare in the UK. Four confirmed cases, and no deaths, have been previously reported in the UK. The last reported confirmed case was in 2014 |
| Further information |
Ebola: overview, history, origins and transmission Ebola virus disease: clinical management and guidance Ebola and Marburg haemorrhagic fevers: outbreaks and case locations NaTHNaC country information page: Democratic Republic of the Congo. |
| Disease or pathogen | Legionella |
|---|---|
| Location | France |
| Status | New incident |
| Reporting date | 23 to 26 August 2025 |
| Summary | On 23 September 2025, the Auvergne-Rhone-Alpes Regional Health Agency reported a cluster of Legionnaires’ disease cases [in French] in Albertville, Savoie department, France. Between 16 and 26 September 2025, 46 confirmed cases [in French] and 2 deaths were reported. Investigations are ongoing to identify the source of exposure. In 2024, 14 Legionnaires’ disease cases were reported in Savoie department. Between 200 and 400 Legionnaires’ disease cases are reported in Auvergne-Rhone-Alpes annually. In the UK, Legionnaires’ disease cases follow a seasonal pattern, with a peak number typically reported between June and October. Between 2017 and 2023, 3,276 cases of Legionnaires’ disease were reported in the UK. In 2023, 212 of 604 confirmed Legionella exposures (35.1%) were related to travel abroad. |
| Further information |
Legionnaires’ disease: guidance, data and analysis NaTHNaC country information page: France |
| Disease or pathogen | Mpox (clade Ib) |
|---|---|
| Location | Senegal and Spain |
| Status | New incident |
| Reporting date | 24 to 26 September 2025 |
| Summary | In Senegal, the WHO reported the first confirmed case of clade Ib mpox. The case is an adult male with a travel history to Kenya. This case was first reported on 23 August 2025 by the Senegal Ministry of Health [in French], however the clade type was not confirmed at the time. On 26 September 2025, the WHO reported the first clade Ib mpox case in Spain. The case had travel history to Tanzania. Media [in Spanish] reported that the case was detected in Madrid and is a 32-year-old male who engaged in sexual activity during his stay in Tanzania. The WHO reports ongoing community transmission of clade Ib mpox in Kenya and Tanzania. In the UK, clade Ib and clade IIb mpox cases have been reported. As of 25 September 2025, 16 clade Ib mpox cases have been reported, all in England. Most of the cases have direct or indirect travel links to countries where clade Ib mpox is circulating. |
| Further information |
Mpox: guidance Mpox clade Ib and clade IIb outbreak: epidemiological overview NaTHNaC country information page: Senegal and Spain |
For more information on the background and methods used in this report, see Outbreaks under monitoring: background and methodology.