Monkeypox cases have been detected in Europe, US, Canada and Australia as the World Health Organization warns countries to be on alert.
France, Belgium and Germany have reported their first cases of monkeypox, joining several other European and North American nations in detecting the disease, endemic in parts of Africa.
Monkeypox was identified 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 circulating, France's health authorities said on Friday.
Separately, the German armed forces' microbiology institute said it has confirmed the virus in a patient who developed skin lesions - a symptom of the disease.
And in Belgium, microbiologist Emmanuel Andre confirmed in a tweet that the University of Leuven's lab had confirmed a second of two cases in the country, in a man from the Flemish Brabant.
With the growing number of detected cases in several European countries, Germany's health agency Robert Koch Institute has urged people returning from West Africa, and in particular gay men, to see their doctors quickly if they notice any chances on their skin.
The rare disease - which is not usually fatal - often manifests itself through fever, muscle aches, swollen lymph nodes, chills, exhaustion and a chickenpox-like rash on the hands and face.
The virus can be transmitted through contact with skin lesions and droplets of a contaminated person, as well as through shared items such as bedding and towels.
The World Health Organization (WHO) has said it was looking closely at the issue and in particular that some of the cases in the UK appeared to have been transmitted within the gay community.
Cases of monkeypox have also been detected in Italy, Portugal, Spain and Sweden as well as in the United States and Canada, leading to fears that the disease - normally concentrated in Central and West Africa - may be spreading.
Monkeypox usually clears up after two to four weeks, according to the WHO.