The global outbreak of monkeypox has been declared a public health emergency of international concern by the World Health Organization (WHO) - the strongest call the agency can make for action.

This marks the seventh time such a statement has been made since 2009, the last of which was for Covid-19. A public health emergency of international concern is defined by WHO's international health regulations as "an extraordinary event which poses a public health risk to other States through the nationwide spread of disease and potentially requires a coordinated international response."

The UN health agency said the term means the situation is serious, unexpected, unusual or has a risk to public health across national borders and may require immediate international attention.

"In short, we have an outbreak that has spread rapidly around the world through new modes of transmission that we understand very little about and that meets the criteria in international health regulations," said Dr. Tedros Adhanom Ghebreyesus, director-general of the WHO. "For all these reasons I have decided that the global outbreak of monkeypox represents a global health emergency of international concern."

Globally, there have so far been more than 16,016 cases of monkeypox – 4,132 of which were reported last week, according to WHO data. The disease has now been reported in 75 countries and territories and has caused five deaths. The Europe region has the highest number of cases in total, with 11,865, and the highest increase in the past seven days, with 2,705.

Dr. Rosamund Lews, technical lead for monkeypox in the WHO's health emergencies programme, said: "There is a lot of work to be done." She added that action must be taken to determine what causes the risk and to reduce the situations that can put people at risk so they can protect themselves. "That's how we're going to get to the bottom of this outbreak," she said.

Monkeypox is a viral infection commonly found in animals in central and western Africa, although it can cause infections in humans. Cases have been identified from time to time in countries where the virus is not endemic, but the latest outbreak has been unprecedented.