A highly contagious digestive virus is surging across the U.S., experts warn.

Rotavirus, a double-stranded RNA virus, causes acute gastroenteritis — inflammation of the stomach and intestines — which can lead to severe diarrhea, vomiting, fever and stomach pain.

The virus primarily affects infants and young children, but there have also been outbreaks in elderly populations, such as nursing homes.

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Data from the Centers for Disease Control and Prevention shows that in the week ending April 4, out of 2,329 rotavirus tests, 7.3% were positive for the infection. Last year’s highest infection rate was 6.77% as of the week ending April 19.

“We’re seeing a lot of rotavirus in the wastewater right now,” Dr. Marc Siegel, Fox News senior medical analyst, confirmed to Fox News Digital. “Testing for rotavirus is way down, but the percentage of positive tests is up.”

While the virus typically peaks in the spring, it is not currently slowing down, he noted.

Why cases may be rising

Patricia Pinto-Garcia, M.D., a medical editor at GoodRx who is based in California, said there are several possible reasons for the rotavirus spike.

“Vaccine rates are down overall among young children, as they decreased during COVID,” she told Fox News Digital. “This means there’s a growing number of infants and young children who are vulnerable to infection.”

The rotavirus vaccine series must be completed by the time a child is 8 months old, she noted.

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As a result of the declining vaccinations, herd immunity isn’t protecting vulnerable children, according to Pinto-Garcia. “Children who haven’t finished the vaccine series yet, are too young to get vaccinated, or can’t get the vaccine due to medical illness are more likely to get exposed to the illness because other children aren’t vaccinated,” she said.

Siegel noted that before the vaccine became available, rotavirus resulted in 55,000 to 70,000 in the U.S. per year.

“I am concerned that the vaccination rate has been declining over the past seven years and is continuing to decline in the current climate of vaccine skepticism,” he said.

Surveillance methods are also much better than they used to be, Pinto-Garcia noted, which means public health experts are able to pick up and track cases better than ever before.

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“But we see that rotavirus-related healthcare visits are also up, so improved detection is not the only reason we are seeing this spike,” she said.

The COVID pandemic also disrupted the pattern of infections, according to Pinto-Garcia, so it’s “tricky” to compare the current levels against older cycles.

“It’s possible that what we are seeing is still some post-pandemic rebound, but it’s unlikely that this year’s pattern is fully explained by just this factor,” she added.

Transmission and risk

Dr. Zachary Hoy, a pediatric infectious disease specialist at Pediatrix Medical Group based in Nashville, Tennessee, often sees young patients with rotavirus.

“Rotavirus is spread via the fecal-oral route, meaning that a person comes into contact with virus droplets from contact with other children or adults, or from contact with objects such as toys that have been contaminated with the virus from someone who is sick,” he told Fox News Digital. “This can lead to outbreaks, especially at schools where many young children share the same toys.”

“It’s possible that what we are seeing is still some post-pandemic rebound, but it’s unlikely that this year’s pattern is fully explained by just this factor.”

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Rotavirus is associated with many dehydration cases in the hospital due to the degree of diarrhea, according to Hoy.

In some severe cases, the virus can lead to seizures due to electrolyte imbalances from dehydration and loss of electrolytes in the stool.

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“Younger children do not have the reserves that older children and adults have, so they can become more dehydrated quicker and develop more severe electrolyte imbalances, leading to more severe infections,” Hoy said.

“Patients with problems with their immune systems or on medications that can decrease their immune systems can have more severe and prolonged infections, too.”

Treatment and care

Because rotavirus is a viral infection, antibiotics are not effective against it. There is no specific antiviral treatment for the condition, with doctors typically recommending supportive care.

“The mainstay of treatment is hospitalization for rehydration via intravenous (IV) fluids,” Hoy told Fox News Digital. “Sometimes it can take up to two to three days of IV fluids to help get patients rehydrated.”

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Blood draws are often necessary to evaluate patients’ electrolyte levels, such as sodium, potassium, calcium and magnesium, according to the doctor.

“If these electrolyte levels are significantly low, sometimes patients need special IV solutions or individual electrolyte medications,” he added.

Dr. Daniel Park, medical director of the Pediatric Emergency Department at UNC Health in Chapel Hill, North Carolina, noted that most children recover with supportive care, but parents should seek medical attention if a child shows signs of dehydration. Those include decreased urination, lethargy or inability to keep fluids down.

“While rare, rotavirus can be life-threatening in vulnerable populations, especially very young infants or children with underlying medical conditions,” Park told Fox News Digital.

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Prevention strategies

Given the lack of antiviral medications for rotavirus, doctors emphasize the importance of prevention, primarily the vaccine.

There are two rotavirus vaccines – Rotateq (a three-dose series) and Rotarix (a two-dose series). They are given starting at age 2 months as oral drops, not injections, according to Hoy.

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“It’s important to get the rotavirus vaccines on schedule, because these younger infants are at greatest risk if they get rotavirus,” he advised.

Other recommended prevention methods include handwashing with soap and water.