Mpox Outbreak Spreads to the U.S.

Massachusetts on US map

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Key Takeaways

  • Small outbreaks of a viral infection called mpox are occurring around the world.
  • The United States has one confirmed case, with more expected.
  • According to the World Health Organization, mpox has a low fatality rate of 3-6%.
  • An approved vaccine for mpox is estimated to be 85% effective at preventing the virus.

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.

How Long Does Mpox Last?

Mpox lasts for two to four weeks and can be treated with antiviral drugs and drugs to bring down a fever and control pain. Once the blisters have scabbed over and dried, the person is no longer infectious.

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.

What This Means For You

Despite all the headlines about mpox, your risk of contracting the virus is still low. If you do get mpox, your symptoms will typically resolve after two to four weeks.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. 2022 United States monkeypox case.

  2. World Health Organization. Multi-country monkeypox outbreak in non-endemic countries.

  3. Food and Drug Administration. Jynneos.

  4. Centers for Disease Control and Prevention. Monkeypox and smallpox vaccine guidance.

By Valerie DeBenedette
Valerie DeBenedette has over 30 years' experience writing about health and medicine. She is the former managing editor of Drug Topics magazine.