A new, more contagious strain of the mpox virus, known as Clade Ib, has started appearing in Europe. Switzerland is the latest country to report an infection. This strain was first identified in the Democratic Republic of the Congo (DRC) in 2023 and has already caused thousands of cases in Central Africa.
What is Clade Ib?
Mpox comes in two main types: Clade II and Clade I. Clade II is more common in West Africa and was responsible for the 2022 global outbreak. Clade I is found mainly in Central Africa and is known to cause more severe infections, with a higher risk of death. Clade Ib, a sublineage of Clade I, is more easily spread and seems to affect children more severely.
How Mpox Spreads
Mpox spreads through close skin-to-skin contact. It can cause a range of symptoms, including rashes, fever, headaches, swollen lymph nodes, and respiratory issues. Although the current risk in Europe remains low, the World Health Organization (WHO) declared the outbreak in Africa a global emergency in August 2024.
How the New Mpox Strain is Spreading in Europe
Several European countries have now reported cases of Clade Ib, with Switzerland being the latest.
Switzerland: The First Case in April 2025
Switzerland confirmed its first Clade Ib case in April 2025. The patient had recently returned from Uganda. After diagnosis, the patient immediately isolated, and authorities assured the public that there was no wider risk.
United Kingdom: 11 Cases So Far
The United Kingdom has reported 11 cases of Clade Ib. Most of these cases are linked to travel, but there has been one recent case with no known travel history. In response, the UK government secured 150,000 vaccine doses and opened new vaccination sites across England.
Germany: Household Spread Detected
Germany has reported eight cases between October 2024 and February 2025. Several of these infections spread within households, including to children. However, no cases have been detected in the wider community.
Belgium: Infections Spread Over Several Months
Belgium identified five cases, with the first two infections occurring in December 2024. These involved an international traveler and a child. Additional cases were reported in January and February 2025.
France: Cases Linked to Travel
In France, cases were confirmed in January and February 2025. Most of these were linked to individuals who had contact with travelers from Central Africa. Authorities have warned that new cases are still possible.
Sweden: The First European Case in August 2024
Sweden was the first non-African country to report a Clade Ib case in August 2024. The patient, who was in Stockholm, had traveled to Africa. No further cases have been reported in Sweden.
Global Concern Over Mpox Clade Ib’s Spread
Beyond Europe, Clade Ib infections have also been found in the United States, Canada, Brazil, China, India, Thailand, Oman, Pakistan, Qatar, and the UAE. Health experts are closely monitoring the virus’s spread and its impact.
Despite the increasing number of cases, experts emphasize that the public health risk remains low. Rapid detection and isolation efforts, along with expanded vaccination campaigns, are helping control the situation.
What’s Being Done to Control the Outbreak?
Health authorities around the world are taking steps to control the spread of Clade Ib. These efforts include:
- Increased vaccination campaigns.
- Improved tracking and reporting of new cases.
- Strong isolation protocols for infected individuals.
While the virus remains a concern, authorities are confident that these measures will help keep the outbreak under control.
