On Wednesday, the CDC confirmed a case of monkeypox in a Massachusetts man who recently traveled to Canada.

It wasn’t the first time the US had seen a case of monkeypox, a virus related to smallpox that causes flu-like symptoms and a rash and can sometimes be fatal. Occasionally, health authorities identify isolated cases in people who have recently returned from West or Central Africa, where the disease is more common.

What’s different — and worrying — about this Massachusetts case is that it’s occurring while other countries, where the virus is also rare, are seeing clusters of monkeypox infections.

Since the beginning of May, the UK Health Security Agency has detected a total of 9 cases of the infection and Portugal and Spain have reported 14 and 23 suspected cases respectively. (The numbers are changing rapidly; an Oxford University epidemiologist tweeted a link to a makeshift tracker where you can see the latest numbers.)

With so many monkeypox cases popping up in different countries at the same time, the immediate questions for health officials are whether the cases are related and whether monkeypox is spreading undetected to other communities.

“The concern of public health officials around the world is trying to understand how these are related and what the causes are,” said Agam Rao, an infectious disease specialist and smallpox virus expert at the CDC.

Just weeks after this outbreak, it is too early to say what exactly is going on and if this outbreak has epidemic potential. For now, Rao said, the general public needn’t worry too much. “The risk is still very low,” she said, and the monkeypox strain currently detected is relatively mild.

Two years on from a deeply divisive global pandemic, news of another pathogen spreading unchecked may have some people rushing straight into the sun.

But with monkeypox, the world faces a very different situation than in the early days of Covid-19. In contrast to SARS-CoV-2, monkeypox is a well-known phenomenon. We have more tools for prevention and treatment – far more than we had with Covid-19 at the beginning of the pandemic – and both public health and the general public have a lot of practice in taking measures to prevent the spread of infection. Still, the trajectory of the outbreak remains uncertain, and public health experts remain vigilant.

What is monkeypox?

Monkeypox viruses generally circulate among wild animals in Central and West Africa and are usually transmitted to humans when they eat or have other close contact with infected animals. The virus was first identified in laboratory animals at the CDC in the 1950s (hence its name “monkeypox”), and for a long time thereafter human infections have been sporadic, even in countries where many animals are infected.

That’s partly because monkeypox is related to the smallpox virus, and immunity to smallpox protects against monkeypox. But since 1980, smallpox has been eradicated from humans, and vaccination against smallpox has become rare — and cases of monkeypox in humans are on the rise. It’s still rare: According to the CDC, Nigeria has reported 450 cases since 2017, when health officials started seeing more cases in people.

Infection with the monkeypox virus usually causes a flu-like illness with fever, headache, muscle pain, swollen lymph nodes, and skin rash. Although monkeypox is not related to chickenpox, the characteristic rash of monkeypox looks very similar, starting with red patches on the mouth and face, then spreading to the arms and legs. After four to five days, the patches turn into small, fluid-filled blisters that are often tender to the touch, eventually becoming donut-shaped, and beginning to crust over two weeks.

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Studies have shown that the R0 of the virus — the number of people hypothetically contracting a communicable disease from a person infected with that disease — is relatively low, somewhere between one and two.

“It’s not as highly transmissible as something like smallpox or measles, or certainly not Covid,” said Anne Rimoin, an infectious disease epidemiologist at the University of California, Los Angeles with expertise in monkeypox and other emerging diseases.

Transmission can occur through close contact with an infected person’s bodily fluids, wounds, or objects that have touched fluids or sores (such as bedding); The virus can also spread via respiratory droplets or aerosols that remain in the air. But unlike Covid-19, where those infected can spread the disease before they get sick, Monkeypox is not considered contagious until humans develop symptoms.

There are two predominant strains of monkeypox: the “West African” version and the “Congo Basin” version. Of the two, the Congo Basin version has historically spread more easily from person to person and caused more deaths. The current outbreak affects the West African version.

Infection is not usually fatal in resource-rich countries like the United States because people living there generally have better access to the supportive care that resolves most monkeypox infections, Rimoin said. In 2003, at least 53 people in the Midwestern United States contracted the infection from pet prairie dogs that became infected while housed near rodents imported from Ghana; None of those infected died.

In rural parts of Africa, where access to hospital care is less, the infection has killed about 4 percent of people infected with the virus.

Several treatments approved for smallpox treatment could potentially be used to treat monkeypox infections if needed. However, most cases are relatively mild; It is unclear whether any of the currently affected patients required or received any of these drugs.

What’s different about the latest monkeypox cases?

The latest clusters of monkeypox cases differ in a number of ways from previous clusters.

First of all, the current cluster includes many infections occurring simultaneously outside of African countries where the disease is circulating in wildlife. “We’ve never had a situation where so many cases have been occurring at the same time outside of these countries,” Rao said.

What is also unusual about the recent cases is that many of them have so far occurred in men who have sex with men (monkeypox transmission has not previously been associated with sexual preference or intimate contact). Many of the cases have clusters of pimple-like spots in the genital area – an unusual area for the monkeypox rash to begin.

After doctors made the first few diagnoses in men who presented to sexual health clinics with unusual skin rashes, health officials began asking sexual health clinics to keep an eye out for cases of monkeypox. This does not mean that monkeypox only circulates among men who have sex with men, and some infections have been diagnosed in people who are not gay or bisexual men.

“We find what we’re looking for,” Maria Van Kerkhove, a World Health Organization expert on emerging diseases and zoonoses, said in an interview with STAT.

Linking this monkeypox outbreak to male sexual networks doesn’t necessarily mean it’s a sexually transmitted infection; it can simply be a question of who gets close enough to an infected person to infect themselves. Other germs spread from nearby – but not specifically sexually – Contact has previously resulted in clusters of infection among gay and bisexual men and college-age students, such as Meningitis, a disease transmitted by respiratory droplets in confined spaces.

How concerned should the general public be about this outbreak?

In addition to trying to understand the cause of the current outbreak and how it is transmitted, health authorities are working to sequence the viruses isolated from individual patients to better understand if they have changed in any way that makes them more or differently transmissible could. said Rao.

For now, however, there’s no reason to believe the virus has undergone a meaningful mutation, she said.

At this time, the general public need not be particularly concerned about the risk monkeypox poses to themselves and their loved ones. “It doesn’t spread easily from person to person, the risk to the general public is low,” Rimoin said. And with healthcare providers now on high alert for the infection, people who do contract it are more likely to be detected quickly and contained quickly, halting chains of transmission.

“We would need to see a significant accumulation of cases, events and ongoing transmission” before public health officials take full preventive action, Rimoin said.

Even a large monkeypox outbreak would likely be much easier to handle than the Covid-19 pandemic. For one, the fact that the virus isn’t considered contagious until people show symptoms could make it harder for people to spread it unknowingly. And in addition to treatments, we already have excellent vaccines to protect those at highest risk of infection – health authorities in the UK are currently vaccinating close contacts of cases to prevent further spread of the infection.

This isn’t a new disease – so if monkeypox becomes a much larger outbreak than it already is, public health officials are better equipped with tools to deal with it.

In fact, as a result of the Covid-19 pandemic, public health is in a relatively strong position to manage this outbreak.

“I think we’re in a good position to respond to monkeypox because most health departments have staff, laboratory networks and funding from Covid that can be used for emergency response,” said Jay Varma, a New York City-based physician and epidemiologist who was recently Senior Advisor to the Africa Centers for Disease Control and Prevention. “The real risk is what happens when that funding runs out in the next few years.”