"This is not a disease that the general population should be worried about, it's not like Covid-19 or other rapidly spreading diseases," WHO Director of Emergency Preparedness Sylvie Briand told reporters.

The official admitted that this is "an unusual situation", with contagions outside the nine African countries where the smallpox family virus is endemic, and that "the number may increase in the coming days, because this event is at the very beginning".

For now, there is no certainty about what could be causing the outbreak: the hypotheses under study are a change in the virus, which seems unlikely given the analyses of infected people already carried out, or a change in human behaviour, which is more likely but is yet to be established, said Sylvie Briand.

Assuming "the uncertainty about the future of the disease", she said she expected the outbreak to be "self-contained", as is the case in countries where the virus is endemic, indicating that the real extent of the contagion is unknown, since surveillance methods are different.

"Usually, we don't have cases or there are very sporadic cases exported to non-endemic countries, but more and more cases are appearing", she pointed out.