The World Health Organization has said another 50 suspected cases are being investigated – without naming any countries – and warned that more cases are likely to be reported.
The virus does not spread easily between people and the risk to the wider public is said to be very low.
In a statement on Friday, the WHO said that the recent outbreaks “are atypical, as they are occurring in non-endemic countries”.
It said it was “working with the affected countries and others to expand disease surveillance to find and support people who may be affected”.
The WHO also warned against stigmatising groups because of the disease.
“It can be a barrier to ending an outbreak as it may prevent people from seeking care, and lead to undetected spread,” it said.
WHO’s Europe regional director Hans Kluge warned that “as we enter the summer season… with mass gatherings, festivals and parties, I am concerned that transmission could accelerate”.
The first case of the disease in the UK was reported on 7 May. The patient had recently travelled to Nigeria, where they are believed to have caught the virus before travelling to England, the UK Health Security Agency said.
There are now 20 confirmed cases in the UK, Health Secretary Sajid Javid said on Friday.
Authorities in the UK said they had bought stocks of the smallpox vaccine and started offering it to those with “higher levels of exposure” to monkeypox.
Spanish health authorities have also reportedly purchased thousands of smallpox jabs to deal with the outbreak, according to Spanish newspaper El País.
Australia’s first case was detected in a man who fell ill after travelling to the UK, the Victorian Department of Health said.
In North America, health authorities in the US state of Massachusetts confirmed that a man has been infected after recently travelling to Canada. He was in “good condition” and “poses no risk to the public”, officials said.