Europe is scrambling to deal with a potential surge in mpox cases over the coming weeks after the first diagnosed case was announced in Sweden this week.

Europe’s top health agency has sparked concern after raising its risk alert level for mpox on Friday.

The European Centre for Disease Prevention and Control (ECDC) now sees a “moderate” risk of mpox, compared to “low” earlier, for the general population in Europe. It said it was “highly likely” that more cases would emerge in the coming weeks.

Meanwhile, health experts in the UK believe that the mutant strain of mpox, Clade 1b, may already be in the UK.

It is thought that there could be as many as “hundreds or even thousands of cases” in the country since the virus may be spreading asymptomatically, according to an expert. The deadly strain, which has a death rate of around five percent in adults and ten percent in children, can spread simply through close contact with infected individuals.

Paul Hunter, a professor of medicine at the University of East Anglia, told The Telegraph that it was “likely that we’ve got infections already in Britain”.

Health experts, who have seen the virus spread rapidly in the Democratic Republic of Congo (DRC), have warned there is a significant lag between infection and visual symptoms.

Dr Leandre Murhula Masirkika, who researched the variant in the DRC, said lesions appear two weeks after infections and that before that “symptoms can be as subtle as a headache and fever, so they might be walking around with it and be infectious”.

Professor Trudie Lang, a professor of global health research at the University of Oxford, echoed the fear of an undetected spread in the UK. She said: “People with a milder infection (such as small lesions on their genitalia) could be walking around with it because they don’t know they’re infected. They might get on a plane with it, without knowing and spread it further.”

The ECDC has urged those travelling to parts of Africa affected by the outbreak to consider getting vaccinated against the virus. This covers five Central African states: Burundi, Central African Republic, Congo, Rwanda, Uganda and Kenya.

Several European countries, including the Netherlands, Czechia, Spain, Italy and Ireland, have scrambled to stockpile hundreds of thousands of vaccines in case the cases worsen

Dr Tedros Adhanom Ghebreyesus, director general of the World Health Organization, stressed that the outbreak is “something that should concern us all”. On Wednesday, he announced the agency’s eighth public health emergency of international concern – the same step the UN health agency took for COVID-19, shortly before it became a global pandemic in 2020.