This month, the World Health Organization declared mpox a global health emergency. The virus, formerly known as monkeypox, is spreading rapidly in parts of Africa, particularly the Democratic Republic of Congo. The outbreak there has been fueled by a fresh version of the virus that has also been discovered in Sweden and Thailand.
The rapidly evolving situation has stirred concern and confusion about who is at risk and how the virus spreads. “I understand why there’s concern,” said Dr. Taimur Khan, associate director of medical research at Fenway Health, a medical center in Boston. But he added, “We’re not surprised in the same way that we were with Covid-19. This is a virus that we’re familiar with, to some extent, and we have the tools.”
We asked Dr. Khan and other experts to answer common questions about the virus.
What do we learn about how mpox spreads?
As the virus has evolved, our understanding of how it circulates has also evolved, said Dr. Rosamund Lewis, technical lead for the World Health Organization’s global mpox response team.
In the 2022 outbreak, many cases were caused by sexual contact. The newer version of the virus still spreads through sex, but experts say it circulates in other ways as well. These could potentially include skin-to-skin contact, contact with infected animals, and touching contaminated surfaces, objects, or fabrics, such as bedding and clothing. Scientists are working to understand how the virus might spread through respiratory droplets and prolonged face-to-face interactions.
“We don’t always know exactly what the mode of transmission was in a given situation,” Dr. Lewis said.
Scientists are still investigating when people are contagious. Some people can spread mpox for days before they feel ill. So far, there is no evidence to suggest that people who never develop symptoms can spread the virus, according to Centers for Disease Control and Prevention.
Who is most at risk?
The greatest risk is in Central and East African countries, especially the Democratic Republic of the Congo and bordering countries.
“Right now, the risk to Americans is extremely low,” said Dr. Carlos del Rio, an infectious disease specialist at Emory University.
Healthcare workers and people in the same household as someone with MPox are susceptible to infection. Because the virus spreads so effectively through intimate contact, people with multiple sexual partners are at greater risk of contracting the virus.
Why is the disease more severe in some people than in others?
Mpox can cause painful rashes, fever, headaches, muscle pain, swollen lymph nodes and other symptoms. Most people recover from Mpox within a month, but the virus can be deadly. The version currently spreading in Africa appears to cause more severe disease and be more deadly than the version that spread in 2022.
Babies and children are more likely to become seriously ill, partly because their immune systems are still developing. “Children get ill much more severely and much more quickly,” said Dr. Lewis. Most of the deaths in the Democratic Republic of Congo have been among children under 15.
People with weakened immune systems, especially those with untreated HIV, are also at greater risk of becoming seriously ill because their immune systems cannot effectively fight the virus. Getting the virus during pregnancy can lead to complications, including miscarriage.
What is the situation in the United States?
The newer version of mpox that is spreading in Africa has not yet been detected in the United States. But people are still catching the version that spread widely in 2022. While the number of cases in America is lower now than during that outbreak, there have been more than 1,700 cases nationwide this year — more than twice number at this time last year.
“People are still getting ill, and they’re less likely to talk about their experiences of being ill because it’s no longer common,” said Joseph Osmundson, an assistant clinical professor of biology at Up-to-date York University.
Who should get vaccinated? How long does the vaccine protect?
Global health officials have raised concerns about gaps in vaccine access: Although the Democratic Republic of Congo is the epicenter of the current outbreak, for example, there are no vaccines there. Vaccines are more widely available in wealthy Western countries.
“Honestly, our most essential task right now is to try to limit the epidemic to Africa and send vaccines there,” Dr. del Rio said.
But the renewed attention to mpox could also encourage eligible people in the United States to get vaccinated. The Centers for Disease Control and Prevention recommends that some men who have sex with men, transgender people, and nonbinary people get vaccinated, including those who have multiple sexual partners or who have had sexually transmitted diseases. People who know or suspect they have been exposed to someone with mpox should also get vaccinated.
Experts said some other groups may also want to get vaccinated, including women who have sex with bisexual men. “If you’re in queer sexual networks, regardless of your identity, you can get vaccinated,” Dr. Osmundson said.
The CDC has online catalog people can employ to find mpox vaccines near me. People should receive two doses, at least 28 days apart; if someone has only received one dose, it is never too slow to get a second. Studies have shown that two doses of the vaccine can reduce the risk of infection by 66 to 88 percent.
Scientists are now studying how long that protection lasts. “We can’t promise that the vaccine will be effective forever,” said Dr. Kelly Johnson, an infectious disease specialist at the University of California, San Francisco. People can get mpox even if they’ve been vaccinated, she said, but those cases tend to be milder. She compared mpox vaccines to Covid shots.
“There’s a very good chance that if you get Covid and you’re vaccinated, you’re not going to be one of those people who gets very seriously ill,” she said. “I think that’s a very similar message with mpox.”