Research and analysis

Outbreaks under monitoring: week 37 (week ending 13 September 2026)

Updated 17 September 2026

Epidemiological week 37, 7 to 13 September 2026

Disease or pathogen	Bundibugyo virus disease (BVD)
Location	Multi-country
Status	Update
Reporting date	15 May to 13 September 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 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 13 September 2026, 7,258 confirmed cases and 3,510 confirmed deaths have been reported in the DRC. This is an increase of 501 confirmed cases and 243 deaths since the last Outbreaks Under Monitoring report. Cases have been reported in 62 health zones across 7 provinces (Ituri, North Kivu, South Kivu, South-Ubangi, Haut-Uele, Bas-Uele and Tshopo). Although most cases have been reported in Ituri (5,659 cases, including 2,583 deaths), a decrease in the number of newly reported cases has been observed since August 2026, while an increase has been reported in North Kivu. This has become the largest recorded BVD outbreak and is the second largest Ebola disease outbreak to date. On 27 August 2026, WHO and the Africa Centres for Disease Control and Prevention declared the end of the outbreak in Uganda following no new cases since the last case was discharged from care on 16 July 2026. A total of 20 confirmed cases (including 2 deaths) were reported in Uganda. Of the confirmed cases, 15 were imported from the DRC and five 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 countries with land borders adjoining the DRC, and low for the remaining countries in the African region, and globally. As of 13 September 2026, no imported cases associated with this outbreak have been reported in the UK. Previous experience from the 2014–2016 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

Disease or pathogen	Crimean-Congo haemorrhagic fever (CCHF)
Location	Mauritania and Senegal
Status	New and update
Reporting date	30 August 2026
Summary	On 30 August 2026, Africa Centres for Disease Control and Prevention reported 2 new confirmed CCHF cases in Mauritania and Senegal. On 27 August 2026, Mauritania’s MoH reported a new outbreak of CCHF in Rosso district, Traza region, following the confirmation of a case in a 50-year-old woman who presented with symptoms of fever, headache, myalgia and bloody diarrhoea on 24 August 2026. The case had reported no tick bites, but had exposure to cattle, sheep and goats. Cases of CCHF have been reported in Mauritania previously, with the last confirmed human case detected in 2023. In the week ending 30 August 2026, Senegal’s MoH reported one confirmed case of CCHF in Keur Massar region. This brings the total number of cases reported in 2026 to 7, across 6 regions. In 2025, a total of 8 CCHF cases were reported in Senegal. CCHF is not present in the UK, nor are there any identified established populations of Hyalomma ticks, the principal vectors of CCHF virus. Confirmed CCHF cases have been imported into the UK, including one fatal case in 2012 and one in 2014.
Further information	Crimean-Congo haemorrhagic fever: origins, reservoirs, transmission and guidelines HAIRS risk assessment: Crimean-Congo haemorrhagic fever NaTHNaC country information page: Mauritania and Senegal

Disease or pathogen	Dengue
Location	Italy and the United States of America
Status	New
Reporting date	30 August to 8 September 2026
Summary	Between 30 August and 5 September 2026, the Florida Department of Health, United States of America, reported 38 cases of locally acquired dengue, bringing the total for 2026 to 111. The highest number of cases has been seen in Hillsborough County (95). Dengue serotype 2 and serotype 3 have been identified among the cases. In 2025, 62 locally acquired dengue cases were reported in Florida. On 1 September 2026, the first locally acquired dengue cases in Italy for 2026 were reported by the Italian National Institute of Health. By 8 September 2026, a total of 24 confirmed locally acquired cases were reported from Livorno province in Tuscany (20 cases), and Lecce Province in Puglia (4 cases). In 2025, a total of 4 locally acquired dengue cases were reported in Italy. There is currently no evidence of local dengue transmission in the UK, or of established populations of the mosquito that transmit the virus. Cases reported in the UK have been related to travel abroad.
Further information	Dengue fever: guidance, data and analysis Travel-associated infections reports HAIRS risk assessment: Dengue NaTHNaC country information page: Italy and the United States of America

Disease or pathogen	Mpox
Location	Ukraine
Status	New
Reporting date	3 September 2026
Summary	On 3 September 2026, the Center for Public Health of the Ministry of Health of Ukraine reported a confirmed case of clade Ib mpox in Vinnytsia. The case is an individual who had travelled to a country in the European region with a history of clade Ib mpox detections. In response, health authorities carried out contact tracing and found no evidence of onwards transmission. This is the first reported case of clade Ib mpox in Ukraine. Clade II mpox has been reported in Ukraine previously. In the UK, cases of clade Ib and IIb mpox continue to be reported. Up to 31 August 2026, 168 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: Ukraine