Research and analysis

Outbreaks under monitoring: week 21 (week ending 24 May 2026)

Updated 28 May 2026

The following relates to an ongoing outbreak, with data current to 27 May 2026

Disease or pathogen	Bundibugyo virus disease (BVD)
Location	Multi-country
Status	Update
Reporting date	15 to 27 May 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 16 May 2026, the WHO Director-General determined that the outbreak constitutes a public health emergency of international concern. As of 26 May 2026, 1,198 Bundibugyo virus cases (including 1,077 suspected and 121 confirmed) and 263 deaths (246 suspected and 17 confirmed) have been reported in the DRC. Confirmed cases have been reported in Ituri (110 cases), North Kivu (10 cases), and South Kivu (one case) provinces. In Uganda, as of 27 May 2026, 7 confirmed cases (including one death) have been reported. This is an increase of 5 confirmed cases since the last report. The US Centers for Disease Control and Prevention reported that the 5 new cases have clear links to the first 2 confirmed cases. On 22 May 2026, Charite University Hospital in Berlin reported that the citizen of the United States who was medically evacuated from the Democratic Republic of the Congo with Ebola disease, has tested positive for Bundibugyo virus upon confirmatory testing. The case is under observation and receiving treatment in the high-security area of the hospital’s specialised isolation unit. The case’s wife and children, who are classified as high-risk contacts, are currently asymptomatic and quarantined in a separate part of the unit. Initial Ebola PCR tests for the family members were negative. To control the spread of the outbreak, WHO has supported with the deployment of rapid response teams, the delivery of medical supplies and the strengthening of surveillance. Other response activities include infection prevention and control assessments, the set-up of safe treatment centres, and community engagement. On 21 May 2026, the United Kingdom announced that it has allocated up to £20 million in new aid funding to the response to the outbreak. This represents the 17th recorded outbreak of Ebola disease in the DRC since the virus was first identified in 1976, with the last reported outbreak ending in December 2025 in Kasai Province. 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. As of 27 May 2026, no imported cases associated with this outbreak have been reported in the UK. Previously in 2015, an imported case of Ebola virus disease was reported in the UK associated with the 2014 to 2016 West Africa outbreak. The WHO assesses the risk of this event as low at a global level, high at the regional level and very high at a national level. The risk of the current Ebola 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? Algorithm for the management of samples suspected of Ebola Virus Disease (in Spanish) NaTHNaC country information page: Democratic Republic of the Congo and Uganda

Disease or pathogen	Andes virus
Location	Multi-country
Status	Update
Reporting date	27 May 2026
Summary	On 2 May 2026, WHO was notified of a cluster of severe respiratory illness aboard a cruise ship carrying 147 passengers and crew from various countries. The cruise ship departed from Ushuaia, Argentina, on 1 April 2026, and travelled across the South Atlantic. On 2 May 2026, laboratory testing of samples taken from a case confirmed hantavirus infection. Further testing of samples from cases confirmed Andes virus infection. As of 27 May 2026, 13 cases (11 confirmed and 2 probable), including 3 deaths (2 confirmed and one probable) have been reported. The latest confirmed case was a passenger of the cruise ship and is quarantine in Spain. WHO currently assesses the risk of this event to the global population to be low. There is very low risk of hantavirus in the UK. Seoul hantavirus is the only species to have been identified in the UK and does not spread between people. It is possible that rare, travel-associated Andes virus infections may be seen in the UK in individuals returning from places where Andes virus is considered endemic, although none have been reported to date.
Further information	Andes hantavirus: epidemiology, outbreaks and guidance Hantaviruses: characteristics, diagnosis and epidemiology HAIRS risk assessment: hantavirus UKHSA blog: What is hantavirus? How is it transmitted and what are the symptoms? NaTHNaC Hantavirus and Hantavirus cruise ship outbreak NaTHNaC country information page: Argentina, Chile and Uruguay

Epidemiological week 21, 18 to 24 May 2026

Disease or pathogen	Mpox
Location	Taiwan
Status	New
Reporting date	19 May 2026
Summary	On 19 May 2026 (in Taiwanese), the Taiwan Centers for Disease Control reported the first confirmed case of clade Ib mpox in Taiwan. The case was reported to have engaged in high-risk sexual activity while abroad in Thailand. In the UK, cases of clade Ib and IIb mpox continue to be reported. Up to 20 April 2026, 48 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: Taiwan