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Are vomiting or diarrhea signs of monkeypox? What to know about less common symptoms

Does monkeypox cause gastrointestinal symptoms such as vomiting and diarrhea? Experts explain what we know so far.
/ Source: TODAY

Monkeypox can cause a variety of symptoms, especially in the early stage before the characteristic rash appears. Some of these early signs may look similar to other illnesses including influenza or COVID-19, experts told TODAY. But what about gastrointestinal symptoms? Are vomiting or diarrhea symptoms of monkeypox?

Monkeypox is a rare viral disease caused by the monkeypox virus, from the same family as the virus that causes smallpox, according to the U.S. Centers for Disease Control and Prevention. It's been spreading around the globe at least since May, with roughly 31,400 cases across 82 countries that haven't historically reported cases of the virus, endemic to Central and West Africa.

As of Aug. 10, there have been 10,393 monkeypox cases in the U.S. in 49 states, according to the CDC.

The virus can spread from animals to humans or between humans. The latter occurs predominantly through close, prolonged skin-to-skin contact, and the virus can spread from an infected person’s lesions, scabs, bodily fluids, respiratory secretions, or contaminated materials, TODAY previously reported.

Up until now, monkeypox outbreaks have been smaller and self-limiting, so the level of human-to-human spread occurring recently unusual, Dr. Stuart Isaacs, infectious disease specialist and associate professor of medicine at the Perelman School of Medicine at the University of Pennsylvania, told TODAY.

How long does it take to show symptoms of monkeypox?

A person who is infected with monkeypox will typically develop symptoms one to two weeks after exposure, but the full incubation period can last up to 21 days, said Dr. Scott Roberts, associate medical director of infection prevention for the Yale School of Medicine, told TODAY. 

What are the first signs of monkeypox?

A textbook case of monkeypox starts out with a set of early flu-like symptoms called a “prodromal” illness, which include a fever, headache, muscle aches, chills, or fatigue Roberts said. 

Swollen lymph nodes, also referred to as lymphadenopathy, is another main symptom of monkeypox, Dr. Paul Adamson, infectious disease physician and assistant clinical professor of medicine at the David Geffen School of Medicine at University of California, Los Angeles, told TODAY. And some patients have been reporting a sore throat and other respiratory symptoms, Adamson added. 

Patients may experience all of these early flu-like symptoms or only a few, according to the CDC, and some people will develop a rash without any prodromal illness at all. 

If one does experience these early flu-like symptoms, the rash will usually appear within five days, but some people experience the prodromal symptoms at the same time as the rash, Roberts noted. In this current outbreak, patients have also reported experiencing prodromal symptoms, such as fever, after the rash appeared, NBC News previously reported.

The rash typically starts out as a flat, red discoloration of the skin which turns into a firm raised bump that becomes filled with pus or fluid, which may be itchy or painful. The lesions eventually scab over and fall off, which can take up to four weeks, Adamson said. 

The lesions typically start out on the face or mouth before spreading to other parts of the body, but they can also remain isolated in the area where contact with an infected person occurred, Roberts said, such as the genital region if monkeypox was transmitted during sexual contact.

How long do monkeypox symptoms last?

Monkeypox symptoms usually last two to four weeks, according to the CDC. The person is no longer infectious once the rash has healed, or when the scabs have fallen off and a new later of skin has formed.

Can monkeypox cause vomiting? Can monkeypox cause diarrhea?

In short: probably not, but it's possible. According to experts and data available from monkeypox patients so far, these are not common symptoms. “I haven’t personally seen vomiting and diarrhea during (the) prodrome or rash stage,” said Roberts.

In a recent observational study of 181 confirmed monkeypox patients in Spain published in The Lancet on Aug. 8, vomiting and diarrhea were not seen in any of the participants, Roberts added. 

However, this does not mean it's impossible for a monkeypox patient to experience vomiting or diarrhea during their illness.

In another study published in the New England Journal of Medicine looking at 528 monkeypox patients diagnosed between April 27 and June 24, 2022, 61 people reported lesions involving the anal mucosa, which was associated with diarrhea, as well as anorectal pain and other symptoms. Nausea and vomiting were not symptoms mentioned in this recent NEJM study, Isaacs pointed out. 

According to an Aug. 10 monkeypox surveillance bulletin from the European Centre for Disease Prevention and Control and the World Health Organization, out of more than 10,000 people diagnosed with monkeypox reporting at least one symptom, just 72 (0.7%) reported experiencing vomiting or diarrhea.

“I don’t know that I have heard those (gastrointestinal) symptoms as a major part of what anyone is experiencing,” Dr. Andrew Goodman, medical director of Callen-Lorde Community Health Center in New York City, told TODAY. “But it’s not the kind of thing where if someone was telling me those are the symptoms they’re experiencing, I would say, therefore, there’s no way (monkeypox) is what you’re dealing with.”

So vomiting or diarrhea wouldn't rule out a monkeypox diagnosis in the early days, but they wouldn’t necessarily point to a diagnosis — especially in the absence of the classic monkeypox symptoms.

“We know a lot of these viral illnesses cause gastrointestinal symptoms for some folks, but not for other folks … but again, there’s just a lot we don’t know,” said Goodman.  

According to WHO, “vomiting and diarrhea leading to severe dehydration, electrolyte abnormalities, and shock” is an uncommon but potentially life-threatening complication of monkeypox. 

Vomiting and diarrhea could also cause severe pain and discomfort for a monkeypox patient with lesions inside their throat, mouth, or rectum. “We worry a lot about genital or anorectal sores causing scarring and problems with urinating, defecating … but so far I haven’t heard that’s been a widespread issue,” Goodman said.

Like COVID-19, what we know now about monkeypox symptoms could evolve as more cases are reported and data is collected.