Research and analysis

Outbreaks under monitoring: week 4 (week ending 25 January 2026)

Updated 5 February 2026

Disease or pathogen	Mpox (clade Ib)
Location	Comoros, Czechia, Madagascar, Nepal and Reunion (overseas department of France)
Status	New
Reporting date	17 December 2025 to 24 January 2026
Summary	The first case of clade Ib mpox in Czechia was reported to the World Health Organization (WHO) on 17 January 2026. The case, who identifies as a man who has sex with men, reported no recent travel history to countries where clade Ib mpox is currently circulating. Investigations are ongoing to determine exposure history, the source of infection and to identify contacts. On 31 December 2025, health authorities in Madagascar declared an outbreak of mpox (in Malagasy) following the country’s first detection on 17 December 2025. Clade Ib mpox infection was confirmed amongst cases by Institut Pasteur de Madagascar on 13 January 2026. As of 24 January 2026, 495 mpox cases have been reported across 20 regions, including 182 confirmed cases. Most cases have been reported in Boeny (267 cases, of which 142 are confirmed). This is an increase in 205 cases, including 104 confirmed cases, since 15 January 2026. On 23 January 2026, the Regional Health Agency of Reunion (in French) reported a travel-associated case of mpox in an individual who had recently travelled to Madagascar. This represents Reunion’s first detection of mpox (clade type is not stated in the report). A travel-associated case of clade Ib mpox from Madagascar has also been reported in Mayotte (in French). On 23 January 2026, the first mpox cases were reported in Comoros. According to the Minister of Health, 4 confirmed mpox cases have been reported, with travel histories to Madagascar.  The clade type is not stated in the report. On 23 January 2025, WHO reported the first case of clade Ib mpox in Nepal. The case recently travelled to the United Arab Emirates , where they initially sought healthcare before returning to Nepal on 7 December 2025. Upon return the case made multiple health facility visits, and mpox was confirmed on 19 December 2025. Case investigation and contact tracing have been initiated. On 22 January 2026, the Africa Centres for Disease Control and Prevention de-escalated the mpox Public Health Emergency of Continental Security. In the UK, clade Ib and clade IIb mpox cases have been reported. Up to 31 December 2025, 21 clade Ib mpox cases have been reported. Most of the cases reported 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: Comoros, Czech Republic, Madagascar, Nepal and Reunion.

Disease or pathogen	Hantavirus
Location	Argentina
Status	New
Reporting date	19 January 2026
Summary	Between 30 June 2025 and 10 January 2026, the Argentinian Ministry of Health (MoH) (in Spanish) reported at least 58  confirmed cases of hantavirus infection, including 20 deaths. This represents a case fatality rate of 34.5% which is the highest reported within the preceding 7 years. According to the Argentinian MoH, there has been a change in the distribution of hantavirus cases at the regional level with cases in the 2025 to 2026 season concentrated in the Central region. Health authorities in the Central region of Argentina, which includes Buenos Aires, Entre Ríos, and Santa Fe, have reported an exceedance in reported cases (56 cases) since a previous peak observed in 2019 (50 cases).
Further information	Hantaviruses: characteristics, diagnosis and epidemiology HAIRS risk assessment: hantavirus NaTHNaC country information page: Argentina