Research and analysis

Outbreaks under monitoring: week 34 (week ending 23 August 2026)

Updated 27 August 2026

The following signal relates to an ongoing outbreak, with data as of 24 August 2026

Disease or pathogen	Bundibugyo virus disease (BVD)
Location	Multi-country
Status	Update
Reporting date	15 May to 24 August 2026
Summary	On 15 May 2026, an outbreak of Ebola disease caused by Bundibugyo virus was declared in the Democratic Republic of the Congo (DRC) and Uganda. On 17 May 2026, the World Health Organization (WHO) Director-General determined that the outbreak constitutes a public health emergency of international concern. The outbreak in DRC remains a public health emergency of international concern as of the latest WHO Emergency Committee meeting, held on 18 August 2026. As of 24 August 2026, 5,656 confirmed cases and 2,715 confirmed deaths have been reported in the DRC. This is an increase of 635 confirmed cases, 337 deaths, and one new reporting province (Bas-Uele) since the last Outbreaks under monitoring report. Cases have been reported in 58 health zones across 6 provinces (Ituri, North Kivu, South Kivu, Haut-Uele, Bas-Uele and Tshopo). The highest number of cases continues to be reported in Ituri (4,716 cases, including 2,119 deaths). This has become the largest recorded BVD outbreak and is the second largest Ebola disease outbreak. On 16 July 2026, Uganda began a 42-day countdown to declaring its outbreak over, after health authorities discharged the last recovered patient. A total of 20 confirmed cases (including 2 deaths) have been reported in Uganda. The last case was reported on 21 June 2026. Of the confirmed cases, 15 were imported from the DRC and 5 were secondary cases among contacts. This is the 17th recorded Ebola disease outbreak in the DRC since the virus was first identified in 1976. The last reported outbreak, in Kasai Province, ended in December 2025. Bundibugyo virus was first identified in 2007 in Bundibugyo district, western Uganda. A second outbreak caused by Bundibugyo virus was reported in DRC in 2012. WHO continues to assess the risk of this event as very high in the DRC, high for Uganda due to cross-border transmission through imported cases and ongoing epidemiological links to the DRC, high for countries with land borders adjoining countries with documented Bundibugyo virus detection, and low for the remaining countries in the African region, and globally. As of 24 August 2026, no imported cases associated with this outbreak have been reported in the UK. Previous experience from the 2014 to 2016 West Africa outbreak suggests a limited importation risk, with only one travel-related case reaching the UK outside of medical evacuations. The risk of the current outbreak to the UK population is assessed as low.
Further information	Ebola: overview, history, origins and transmission Ebola virus disease: clinical management and guidance Ebola and Marburg haemorrhagic fevers: outbreaks and case locations UKHSA blog: What is Ebola and how does it spread? NaTHNaC country information page: Democratic Republic of the Congo and Uganda

Epidemiological week 34, 17 to 23 August 2026

Disease or pathogen	Mpox
Location	Puerto Rico
Status	New
Reporting date	18 August 2026
Summary	On 18 August 2026, media (in Spanish) reported 2 cases of clade I mpox in Puerto Rico. One case reported exposure while travelling abroad to an unspecified country, while the second case reported sexual contact with an individual who had travelled. These cases are not epidemiologically linked and represent the first reported cases of clade I mpox in Puerto Rico. Clade II mpox has been reported in Puerto Rico previously, with 15 cases recorded in 2025. In the UK, cases of clade Ib and IIb mpox continue to be reported. Up to 31 July 2026, 119 clade Ib mpox cases have been reported, most of which 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: Puerto Rico

Disease or pathogen	Swine influenza A(H1N2)v
Location	United States
Status	Update
Reporting date	21 August 2026
Summary	On 21 August 2026, the United States Centers for Disease Control and Prevention reported a second human case of influenza A(H1N2)v infection in Michigan, associated with an agricultural fair. The first case was reported by the Michigan Department of Health and Human Services on 14 August 2026. Both cases are aged under 18 years old and sought medical care during the week ending 15 August 2026. Neither case was hospitalised and both are recovering. One case received influenza antiviral treatment. Epidemiological investigations found that the cases did not have contact with one another and attended the same agricultural fair where ill swine were present. No additional cases associated with these cases or the fair have been identified. In the UK, one human case of influenza A(H1N2)v was reported in 2023. This was the first detection of this variant in a human in the UK and was detected as a part of routine national influenza surveillance. The case experienced mild illness and recovered. The general population has a very low risk of exposure to influenza A(H1N2)v in pigs in the UK. Those directly exposed to pigs regularly (for example, through occupation) may have a higher risk of exposure.
Further information	Influenza A(H1N2)v: guidance for affected members of the public Influenza A(H1N2)v: rapid technical assessment Influenza (avian and other zoonotic) NaTHNaC country information page: United States

Disease or pathogen	West Nile virus (WNV)
Location	European Region
Status	New
Reporting date	21 August 2026
Summary	In 2026, up to 21 August, 625 locally acquired human cases of WNV have been reported across 12 countries in the European Region. Notably, this includes the first 2 locally acquired cases in the Netherlands since 2020, and a higher number of cases in Greece, North Macedonia and Spain when compared to 2025. As of 21 August 2026, 157 locally acquired cases have been reported in Greece in 2026. This represents an increase in cases when compared to the total number of cases recorded in 2025 (96 cases). On 21 August 2026, the Greek National Public Health Organisation (in Greek) published an alert regarding the circulation of WNV in the 2026 transmission period. The alert highlights the region of Attica which has recorded a higher number of cases when compared to previous years. A peak in WNV cases is reported annually between mid-August and early September in Greece, therefore additional cases should be expected in the coming weeks. Additionally, as of 21 August 2026, 37 locally acquired cases have been reported in North Macedonia in 2026. This is a higher number of cases when compared to all of 2025 (2 cases). Similarly, during this time period, 63 locally acquired cases have been reported in Spain, surpassing the total number of cases reported in 2025 (36 cases). In 2025, the European Centre for Disease Prevention and Control reported that Europe is experiencing longer and more intense transmission seasons for mosquito-borne diseases, including West Nile virus. This shift is driven by climatic and environmental factors such as rising temperatures, longer summer seasons, milder winters and changes in rainfall patterns which create favourable conditions for mosquitoes to thrive and transmit viruses. In 2025, a total of 1,112 locally acquired human cases of WNV were reported across 14 countries in the European Region, of which most cases were reported in Italy (779 cases). No known locally acquired human WNV cases have been reported in the UK. However, there is an existing risk to UK residents who travel to endemic areas abroad. Between 2000 and June 2025, 7 confirmed WNV cases were recorded in UK residents, all acquired through travel. The probability of human infection with WNV in the general UK population is currently considered, at most, very low. For higher risk groups including individuals living, working or visiting areas with active human-biting mosquito vectors co-located with infected birds, the probability of infection would be considered low.
Further information	HAIRS risk assessment: West Nile virus West Nile virus: epidemiology, diagnosis and prevention Surveillance and updates for West Nile virus infection NaTHNaC country information page: Greece, Netherlands, North Macedonia and Spain