On Saturday, the World Health Organization declared the outbreak, which has infected nearly 16,000 people in 72 countries, a global health emergency — the loudest alarm it can set.
Monkeypox, so named because it was first discovered in a monkey, is related to the deadly smallpox virus, which was eradicated in 1980, but is much less severe.
The strain currently circulating outside of Africa is the lightest of the two known versions. Monkey pox was first identified in 1970 in Zaire (now the Democratic Republic of the Congo) in a nine-year-old boy.
It becomes endemic to the tropical rainforests of Central and West Africa, where 11 countries have reported cases.
The virus is transmitted through close contact with infected animals, mostly rodents or humans.
In June 2003, the disease appeared in the United States – the first time it had been detected outside Africa.
It is believed that the disease spread after it became infected with prairie dogs imported by rodents from Ghana to the United States.
The US Centers for Disease Control and Prevention (CDC) has reported 87 cases but no deaths.
The year 2017 caused a major outbreak in Nigeria, with more than 200 confirmed cases and a mortality rate of about three percent, according to the World Health Organization.
Over the next five years, sporadic cases were reported worldwide for travelers from Nigeria, particularly in Britain, Israel, Singapore and the United States.
In May 2022, a wave of cases was detected in countries outside Africa, of people who had no travel links to the region. Most of those affected are gay men.
Europe is the epicenter of the new outbreak.
By May 20, Britain had recorded 20 cases, most of them among gay men.
On the same date, the World Health Organization counted 80 confirmed cases around the world, including Australia, Belgium, Canada, France, Germany, Italy, Portugal, Spain and Sweden.
On May 23, the United States said it was preparing to give smallpox vaccines, effective against monkeypox, to people who have been in close contact with monkeypox patients.
Three days later, the European Union said it was centralizing vaccine procurement, as it had done with Covid-19.
In early June, the head of the World Health Organization, Tedros Adhanom Ghebreyesus, said that more than 1,000 confirmed cases of monkeypox had been reported to the WHO from 29 countries where the virus is not normally found.
On June 21, Britain announced plans to offer vaccinations to gay and bisexual men with multiple sexual partners.
WHO experts meet on June 23 to discuss the threat but have determined that monkeypox does not constitute a global public health emergency.
On July 8, health authorities in France also launched preventive stings for people considered at risk, including gay, transgender and sex workers.
On July 14, the US Centers for Disease Control and Prevention reported more than 11,000 confirmed cases in about 60 countries where monkeypox is not usually found. Most cases are in Europe, the United States and Canada.
The number of infections in New York doubles in less than a week to several hundred. People are queuing to get their vaccines, which are in short supply.
On July 20, Tedros announced that nearly 14,000 confirmed cases of infection have been reported to the World Health Organization this year, from more than 70 countries, with five deaths, all in Africa.
He says six countries reported their first cases in the previous week, while some states have limited access to diagnostics and vaccines, making it difficult to track and stop the outbreak.
The World Health Organization is calling for a new expert meeting on July 21 to decide whether to declare a global health emergency.
On Saturday, Tedros declared the monkeypox outbreak a “public health emergency of international concern.”
Watch WHO declares monkeypox a global health emergency as infection rates soar