Mpox Outbreak Spreads to the U.S.

Cases of mpox (formerly known as monkeypox)—a viral disease that causes fever, swollen glands, and a painful, blistering rash—have been identified in the United States.

The Centers for Disease Control and Prevention (CDC) has confirmed a case in Massachusetts and is investigating possible cases in New York City, Florida, and Utah. Outbreaks are also occurring in Canada, the United Kingdom, Australia, and several countries in Europe.

However, your risk of contracting mpox is still low.

“Monkeypox has never caused a sustained outbreak in the United States,” Robert Amler, MD, former chief medical officer at the CDC’s Agency for Toxic Substances and Disease Registry, told Verywell via email. “It is most prevalent in Western and Central Africa, and mostly spread by animal contact, scratches, and bites—most commonly from rodents and occasionally from close contact with an infected human or by handling bushmeat.”

What Is Mpox?

Mpox is caused by a virus that is a close—but milder—cousin of smallpox. According to the CDC, it was first identified in 1958 in Africa in monkeys being used for research, and was first diagnosed in a human in 1970.

Most outbreaks since then have occurred in Africa. Cases outside of Africa are usually identified in people who have been traveling internationally or have been in contact with imported animals.

It is unlikely that mpox would go unrecognized by physicians or other healthcare workers in the U.S., Amler said.

“The blistering rash and swollen lymph nodes are quite pronounced and unlikely to be missed,” he explained.

Why Is Mpox Spreading Now?

Because there isn’t usually much person-to-person transmission, outbreaks of mpox are generally easy to stop, Hannah Newman, MPH, director of infection control at Lenox Hill Hospital in New York, told Verywell.

However, outbreaks in Europe and Australia may involve more person-to-person transmission, which can occur through touching or other close contact with bodily fluids, she noted.

“This time around, we’re seeing a bit more evidence of transmission by sexual encounters,” she said. “There has been more evidence of person-to-person transmission, but it’s nothing close to what we see with illnesses like flu, COVID-19, or measles.”

The CDC says that cases in Europe and North America have included men who say they have had sex with men. But it’s important to note mpox is not a sexually transmitted infection—it’s just spread through prolonged close contact, including through respiratory droplets from sneezes or coughs.

Is There an Mpox Vaccine?

In 2019, the Food and Drug Administration (FDA) approved a vaccine called Jynneos for preventing both smallpox and mpox. The vaccine, which is up to 85% effective at preventing mpox, requires two injections four weeks apart.

Right now, the vaccine is only approved for us in people age 18 and older who are determined to be at high risk for smallpox or mpox. But the CDC's Advisory Committee on Immunization Practices (ACIP) is currently evaluating who else may benefit from the shot.

Jynneos is also an option for treating mpox. The CDC says that if the vaccine is administered within four days of exposure, it can help prevent the onset of mpox.

CNN reports the Strategic National Stockpile is fielding a request to release the Jynneos vaccine. Over 1,000 doses are currently available.