Still, at a public session on Monday, WHO officials described the outbreak as “containable” and cautioned against stigmatizing affected groups, saying the disease can infect anyone. The agency’s Europe director warned that festivals and parties could accelerate spread. agency said the outbreak is “a highly unusual event” and said the fact that cases are being seen in so many different countries suggests the virus may have been silently spreading for some time. Heymann chaired an urgent meeting of WHO’s advisory group on infectious disease threats on Friday to assess the outbreak and said there was no evidence to suggest that monkeypox had mutated into a more infectious form. In recent years, the illness has been fatal in up to 6% of infections. Vaccines against smallpox, a related disease, are effective in preventing monkeypox and some antiviral drugs are being developed.