Monkeypox is named for the animals in which it was discovered, but the WHO intends to rename it after scientists deemed the current one “discriminatory and stigmatizing.” The disease cropped up in 1958 among monkeys kept for research, according to the CDC — more than a decade before a human case was identified in the Democratic Republic of Congo. Mass vaccination against smallpox “presumably” curbed monkeypox infections for a time among humans, researchers wrote in a 2005 article. But cases resurged, partly because of a lack of immunity in later generations, they say. More than 450 cases have been reported in Nigeria since 2017, according to the CDC. Monkeypox infections typically last two to four weeks, the CDC says, and begin with flu-like symptoms and swelling of the lymph nodes. Eventually fluid-filled bumps — or “pox” — spread across the skin. Health officials have noted that the latest monkeypox cases often involve genital rashes that can be confused for syphilis or herpes. The disease can spread through contact with animals, infected people and materials used by infected people, health authorities say. Examples listed by the CDC include contact with bodily fluids, contact with monkeypox sores and infection through “respiratory droplets” in a “close setting” such as a shared household. CDC officials say lesions are the most significant source of spread, such as skin-to-skin contact with a person with rashes or sharing bedding or clothing exposed to lesions, and that respiratory spread happens during prolonged face-to-face contact when a person has lesions in their mouth or throat. Monkeypox can be deadly, but two major strains of the virus pose different risks. About 1 in 10 people infected with a Congo Basin strain have been found to die, according to the WHO, while a West African strain appeared to be fatal for about 1 in 100 people infected. That milder strain is the one infecting people who were hospitalized in Britain, health authorities said.

How worried should we be? How does this compare to coronavirus?

Experts stress that monkeypox is different from the coronavirus that has infected millions. Monkeypox is highly visible, making contact tracing and isolation easier. An existing smallpox vaccine could help protect the public if needed, Katzourakis said. And “we don’t have the potential for something spreading through the globe at anything like the kind of rate that we saw with covid,” he said, because monkeypox transmits less easily between humans. Still, the latest spate of cases stands out, Katzourakis said. The longer it continues, the more chance the virus has to mutate and improve its transmissibility. “It’s either a lot of bad luck or something quite unusual happening here,” Katzourakis said. Outbreaks of monkeypox have typically been small, with cases in the single digits, said Inglesby, of the Johns Hopkins Center for Health Security. “So I think the risk to the general public at this point, from the information we have, is very, very low.” But he agreed recent cases raise many questions. “We don’t really have the sense yet of what’s driving it. … There isn’t a travel link that’s identified that brings these cases all together,” he said. Monkeypox is known to spread through human contact with animals such as rodents or primates, but the virus has spread further this year through human-to-human transmission than previously reported. Health officials have noted recent cases among men who have sex with other men — a pattern that is crucial to understand, Inglesby said, as officials have not previously considered sexual orientation to be a risk factor for monkeypox. The risk to the public remains low, authorities say. The WHO is developing new guidance and has a theory that the spread appears to be driven by sexual contact, David Heymann, chair of the agency’s Strategic and Technical Advisory Group on Infectious Hazards with Pandemic and Epidemic Potential, told Reuters in May.

Is the smallpox vaccine effective against monkeypox? should I get it?

Data suggests that the smallpox vaccine is about 85 percent effective against monkeypox, according to the CDC . Although the smallpox vaccine stopped being administered to the U.S. general public in the 1970s — years after the disease was eliminated in North America — a supply was kept on hand. A new vaccine, ACAM2000 , replaced the old one in the mid-2000s. In 2019, JYNNEOS was approved to prevent smallpox and monkeypox in high-risk adults 18 and older. Federal officials say that the United States has enough vaccine doses and that the CDC is working on guidance for administering them. The vaccines are available for people at risk for occupational exposure, such as those working in laboratories, or who may come into contact with orthopoxviruses. (Orthopox is the genus of virus to which monkeypox belongs.) People in the general population who have been exposed to the monkeypox should get one of the vaccines, said Ruth Karron, a professor and director of the Johns Hopkins Vaccine Initiative at the Bloomberg School of Public Health. And, she said, because the incubation period for monkeypox is long — up to two weeks — some data suggests that people who get vaccinated after exposure or infection may be able to avoid illness or experience a milder case. The CDC recommends that people get vaccinated within four days of exposure to prevent infection, but there may still be benefits up to 14 days. People in this situation should contact their doctor for guidance. As for people who received the smallpox vaccine decades ago, health experts say they may still have some protection against monkeypox, but probably not enough. According to the CDC, those who have not had a smallpox vaccine within the past three years should consider getting one if they are exposed to monkeypox. “We should also bear in mind that we are still trying to figure out what’s going on with monkeypox because this pattern of infection is not one we’ve seen before,” Karron told The Post. “But still, we have very, very, very few cases, and I don’t think we are going to see a large outbreak.” The WHO is discouraging mass vaccination for the virus, which can be treated with antiviral medicines and vaccines stockpiled in the event of a smallpox outbreak, because there is limited clinical data and an insufficient global supply. The U.N. health agency is developing a plan to make vaccines and treatments more accessible. “The global outbreak of monkeypox is clearly unusual and concerning,” WHO Director General Tedros Adhanom Ghebreyesus said Tuesday.

Had monkeypox made it to the United States before?

Monkeypox made its way to the United States — and the Western Hemisphere — for the first time in 2003, researchers say . More than 70 cases were reported in the Midwest, mostly among people who were exposed to prairie dogs apparently infected by rodents from Ghana, according to the CDC . Two children fell seriously ill and recovered, the CDC said. The infection reported May 18 in Massachusetts was the first case of monkeypox identified in the United States this year, health officials said. Several states have reported cases since. Texas and Maryland reported one infection each last year in “people with recent travel to Nigeria,” the Massachusetts Department of Public Health said.

The CDC is working with counterparts in other countries to compile information that can answer experts’ many questions. It’s so rare, Johns Hopkins’ Inglesby said, that “most clinicians in America will never see a case in their lifetimes” — so communication about monkeypox will be important in ensuring doctors are watching for symptoms.

Because of global trade and travel, poxviruses are able to spread farther, experts said. The eradication of smallpox in 1980 has helped remaining poxviruses slip past waning protections, said Anne Rimoin, an epidemiologist at the University of California at Los Angeles who has studied monkeypox for two decades. “No good deed goes unpunished,” Rimoin said in May. “You declare that you can eradicate a pathogen, but you might leave space for another to emerge.” Agam Rao, a CDC medical officer, said that although researchers have found a rise in monkeypox prevalence since the end of the smallpox vaccine campaign, other factors have been linked to the infections, including climate change and other environmental shifts that have led to more human and animal interactions. “We’re at a point right now where we just really need to figure out why this is happening before we can start proposing solutions, like vaccinations,” Rao said in May. “This is just unexpected. It’s not something we would have recommended if you had asked me two weeks ago, because the risk to the general population is extremely rare.” Ana Herrero and Seung Min Kim contributed to this report.

What is monkeypox, the rare virus now confirmed in the U.S. and Europe?

By Meryl Kornfield

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Updated June 15, 2022 at 8:27 p.m. EDT|Published May 18, 2022 at 10:56 p.m. EDT

As monkeypox cases rise in Europe and other parts of the globe, health authorities are expressing concern about the unusual uptick. (Video: Alexa Juliana Ard, Meryl Kornfield/The Washington Post)

As monkeypox cases rise in Europe and other parts of the globe, health authorities are expressing concern about the unusual uptick but also pointing out that the virus is far less transmissible than the coronavirus that upended the world.

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This year, more than 1,600 monkeypox cases have been confirmed and nearly 1,500 more are suspected, according to data that 39 countries — including Canada, several European nations and the United States — sent to the World Health Organization. Most of those, 32, had not previously reported infections, raising concern among the global health community that the virus is not behaving as it normally had.

Last week, the White House said that there were at least 45 cases identified in 15 states and D.C. The number of infections is expected to surpass that of a 2003 outbreak, which would make it the biggest outbreak the United States has faced.

The Centers for Disease Control and Prevention issued an alert last month, urging doctors and state health departments to be vigilant.

Days later, President Biden said that the United States had sufficient vaccines to fight a serious outbreak, and that quarantine would not be necessary to contain the spread.

“I just don’t think it rises to the level of the kind of concern that existed with covid-19, and the smallpox vaccine works for it,” Biden said at a news conference.

The fact that cases are emerging in several countries at once — with signs of “sustained” transmission in people — is striking, said Aris Katzourakis, a professor of evolution and genomics at the University of Oxford. However, epidemiologists note that monkeypox doesn’t spread easily: Outbreaks are generally small, and an existing smallpox vaccine could help protect people if needed.

The general risk to the public is considered “very, very low,” said Tom Inglesby, director of the Johns Hopkins Center for Health Security.