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How contagious is monkeypox? Who's at risk?

Over 3,400 cases of monkeypox have been reported in 45 states. Here's how the virus is transmitted and who's most at risk.

The ongoing monkeypox outbreak was recently declared a public health emergency of international concern by the World Health Organization, the highest alert that the United Nations agency can issue. Almost 18,000 cases of the virus, which normally only circulates in West and Central Africa, have been reported in 69 countries where the disease is not endemic.

In the U.S., 45 states, along with the District of Columbia and Puerto Rico, have reported cases of monkeypox, totaling more than 3,400 cases across the country, according to the Centers for Disease Control and Prevention.

Related: Monkeypox outbreak now in 45 states: These pictures can help identify symptoms

A recent study found that the outbreak is primarily being driven by sex between men. That said, monkeypox isn't considered a sexually transmitted infection, and anyone can get monkeypox, regardless of sexual orientation, according to the CDC. It's also unlikely that the outbreak will stay within the community of men who have sex with men, a WHO spokesperson told CNBC earlier this week.

Here's what you need to about how monkeypox spreads.

How is monkeypox transmitted?

Monkeypox is transmitted through close contact with a human or animal infected with monkeypox, or through a material contaminated with the virus, according to the CDC. The 2003 monkeypox outbreak in the U.S. occurred in people who'd had contact with infected prairie dogs imported from Ghana.

Human-to-human transmission of monkeypox can occur through:

  • Direct contact with a monkeypox rash, or the scabs or bodily fluids of an infected person
  • Respiratory droplets of an infected person from prolonged face-to-face contact, including kissing, cuddling or sex
  • Touching clothing, linens or other items that have come in contact with a monkeypox rash or bodily fluids of an infected person

Pregnant individuals can spread the virus to the fetus, and infected animals can spread monkeypox through scratches or bites, or if a person prepares or eats meat or uses products from an infected animal.

How contagious is monkeypox?

"Monkeypox does not spread easily between people," the European Centre for Disease Prevention and Control, an agency of the European Union, noted. The U.S. CDC also stated, "In the current monkeypox outbreak, we know that those with disease generally describe close, sustained physical contact with other people who are infected with the virus."

Unlike COVID-19, monkeypox isn't believed to have airborne transmission, meaning it doesn't appear to spread through aerosols of an infected person, which linger in the air. Transmission from large respiratory droplets that quickly fall to the ground has been reported, but prolonged face-to-face contact is usually necessary. "Monkeypox is not known to linger in the air and is not transmitted during short periods of shared airspace," according to the CDC.

“It’s not a situation where if you’re passing someone in the grocery store, you’re going to be at risk for monkeypox,” Dr. Jennifer McQuiston, deputy director of CDC’s Division of High Consequence Pathogens and Pathology, said a May CDC media briefing.

NBC News medical correspondent Dr. Natalie Azar said on TODAY that the virus that causes COVID, SARS-CoV-2, is more contagious than monkeypox, as one infected individual can easily give it to a dozen other people.

Another major difference from COVID-19: People infected with monkeypox cannot spread the virus unless their symptoms have started, according to the CDC, whereas a person can be infected with COVID but have no symptoms and still spread it.

“That’s a huge relief, of course, to all of us,” Azar said.

A person with monkeypox is no longer contagious once their rash has healed and a new layer of skin has formed, which usually takes two to four weeks. (Other symptoms, which have historically preceded the rash, include fever, headache, muscle ache and fatigue. But in the current outbreak, not every patient has reported such symptoms.)

Who is at risk of monkeypox infection?

While the CDC has urged the LGBTQ community to be on alert, the greatest risk is to anyone who has had close, physical contact with someone who has monkeypox, such as family members, someone living in the same household or health care workers treating an infection, according to McQuiston.

“Infectious diseases don’t care about borders or social networks. Some groups may have a greater chance of exposure right now, but by no means is the current risk of exposure to monkeypox exclusive to the gay and bisexual community,” added Dr. John Brooks, an epidemiologist in the CDC’s Division of HIV/AIDS Prevention, during the May media briefing. “Anyone can develop and spread monkeypox infection.”

The CDC is recommending vaccination against monkeypox for people who have been exposed to monkeypox and people with a greater risk of being exposed, such as lab workers who test viral samples. The CDC also recommends vaccination for people with presumed cases of monkeypox, such as those who've had multiple sexual partners in the past two weeks in an area where monkeypox is spreading, or those who had sex with someone with monkeypox.

Where is monkeypox being investigated in the U.S.?

Monkeypox has spread to 45 states, the District of Columbia, which has the highest per capita case rate in the country, and Puerto Rico. New York City is considered the epicenter of the U.S. outbreak. New York state has the most monkeypox cases in the country with 990, followed by California's 356 and 344 in Illinois.

If you're worried you're experiencing monkeypox symptoms, see your health care provider right away, especially if they include a new or unexplained rash. You should also remind your provider that monkeypox is circulating and avoid close contact with other humans or animals until you've seen a health care provider, per the CDC. Follow the same precautions until you receive your test results and, if it's positive, until your rash heals.