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Monkeypox appears to have exploded out of nowhere in the past two weeks, spreading across Europe, the Americas, and other regions. But warning signs appear to have gone unheeded.

An unusual and long-running outbreak in Nigeria should have served as notice that it was only a matter of time before this orthopoxvirus pushed its way to the center of the infectious diseases stage, experts say.


After decades without cases, Nigeria experienced a large monkeypox outbreak starting in 2017 that continues to this day. Prior to this year, that outbreak spread beyond Nigeria’s borders eight times, with infected people traveling to the United States, the United Kingdom, Israel, and Singapore.

Chikwe Ihekweazu, the former director general of the Nigeria Centre for Disease Control, said his country sought help to try to decipher what was going on with monkeypox. But the requests didn’t get much traction.

As such, some critical questions about monkeypox — including the true case fatality of the West African clade of the virus, the one circulating now, as well as how many people, on average, each infected person transmits to — remain unclear.


“There wasn’t a lot of interest to support that work until now — sadly,” said Ihekweazu, who was recently named to head the World Health Organization’s new Berlin-based hub for pandemic and epidemic intelligence. “It never really received the interest it needed to answer some of these questions.”

Nigeria has detected 558 suspected cases — 241 of them confirmed — since the current outbreak began in 2017.

Nigerian CDC
Nigerian CDC

“When we saw this emerge suddenly in Nigeria in 2017 out of the blue literally, we were all very surprised,” he told STAT. “In a way, it’s similar to the surprise around the world right now, because it’s a similar scenario. Suddenly from nowhere, we had a lot of cases in the Niger Delta part of Nigeria in the south.”

Further investigation revealed cases around the country, Ihekweazu said. “So very interesting that a virus that we hadn’t seen for about 40 years at the time in Nigeria suddenly appears and appears in multiple places at the same time.”

The Nigerian CDC tried — to date without success — to figure out how people were being infected with the virus. Some small mammals are believed to be the host species of the virus, but efforts to find the virus in the wild have so far failed.

The rest of the world appears to be rapidly catching up with Nigeria. There have been over 300 suspected cases detected since the United Kingdom reported in mid-May that it has diagnosed cases of monkeypox in people who had not traveled to one of the countries in West or Central Africa where the virus is endemic. Of the cases outside of Africa, 219 have been confirmed, the European Centre for Disease Prevention and Control said Wednesday.

Ihekweazu said before the Covid-19 pandemic he tried to raise awareness of the problem monkeypox could pose. In 2019, the London-based think tank Chatham House convened a meeting to discuss the risks, said David Heymann, a professor of infectious diseases epidemiology at the London School of Hygiene and Tropical Medicine, who chaired the meeting. Among them was the possibility of sexual transmission of monkeypox because some people who contracted the virus developed lesions on their genitals or in their genital region.

The current outbreak appears to have taken off when the virus began to transmit among men who have sex with men.

The virus is not transmitted through sex per se; there’s no evidence, for example, that it is passed through semen or vaginal fluids. But the skin-to-skin contact experienced during sex can lead to transmission, if one of the partners has monkeypox lesions.

Anne Rimoin, an infectious diseases epidemiologist at the University of California, Los Angeles, who has studied monkeypox since 2002, agreed with Ihekweazu that people who study poxviruses knew spread of monkeypox was a possibility. The eradication of smallpox in 1980 and the cessation of use of smallpox vaccine — which offers some protection against monkeypox — created an ecological void experts feared another poxvirus might fill.

“There have been a million tabletop exercises and other things, looking at the dissemination of monkeypox, of smallpox, of other poxviruses. This is not a completely unanticipated situation here,” Rimoin said. “We knew all along, as population immunity waned and potentially individual immunity waned for those who were vaccinated, we would potentially see cases of monkeypox or other poxviruses spreading.”

From 2018 onward, there were sporadic instances where travelers infected in Nigeria brought the virus to countries where monkeypox is not found. Ihekweazu said each exportation put recipient countries on high alert to try to prevent domestic spread, with cases treated in high containment facilities while they were infectious. But help to stop the virus from spreading at its source didn’t follow.

“So basically you pull out the army whenever there’s a single case exported. But there’s no interest in working together with the country from which the cases are coming to try and understand it a little bit more,” he said.

He suggested in the aftermath of the Covid pandemic, the world may be more open to understanding the need to nip infectious disease in the bud. “This was all pre-Covid. So … hopefully people’s general sense of these things have changed a little bit that we do pay a little bit more attention.”

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