The disease, which is endemic in parts of Africa, has been identified in Australia and several European and North American countries.
French health authorities said on Friday that monkeypox was found in a 29-year-old man in the Ile-de-France region, which includes Paris, who had not recently returned from a country where the virus is endemic.
Separately, the German Armed Forces’ Institute of Microbiology said it had confirmed the virus in a patient who developed skin lesions — a symptom of the disease.
In Belgium, microbiologist Emmanuel Andre confirmed in a tweet that a laboratory at the University of Leuven had confirmed the second of two cases in the country, a man from the Flemish province of Brabant.
With more cases detected in several European countries, Germany’s health agency, the Robert Koch Institute, is urging people returning from West Africa to see a doctor as soon as possible if they notice any changes in their skin.
Usually not fatal
The rare disease — which is usually not fatal — typically presents with fever, muscle pain, swollen lymph nodes, chills, exhaustion, and a chickenpox-like rash on the hands and face.
The virus can be spread through contact with skin lesions and droplets from a contaminated person, as well as through shared items such as bedding and towels.
The World Health Organization (WHO) said it was watching the issue closely, especially as some cases in the UK appear to be spreading within the gay community.
Cases of monkeypox have also been detected in Italy, Portugal, Spain and Sweden, as well as in Australia, the United States and Canada, leading to concerns that the disease, which is usually concentrated in Central and West Africa, may be spreading.
According to the World Health Organization, monkeypox usually clears up after two to four weeks.