Pediatric hospital beds are filling up as RSV spreads across the US. Here are the symptoms to look out for and who's most at risk of getting seriously ill.

• Difficulty breathing and dehydration could be signs that a child is sick with RSV.
• Confirmed RSV cases in the US have increased in recent weeks.

Difficulty breathing and dehydration are among the signs of respiratory syncytial virus that parents should look out for, doctors say, as pediatric hospital beds fill up across the country amid an unusual outbreak of the illness.

RSV typically causes mild, flu-like symptoms that get better within weeks without treatment, according to the Centers for Disease Control and Prevention. However, it can be serious, especially for infants and older people, with the potential to cause pneumonia and inflammation of the small airways called bronchiolitis, which can lead to respiratory failure and death.

The CDC estimates that around 58,000 children younger than 5 years are hospitalized with the virus each year.

"RSV can be super dangerous for some young infants and younger kids, particularly those that are less than 2 years of age," Dr. Priya Soni, an assistant professor of pediatric infectious diseases at Cedars Sinai Medical Center, told CNN.

CDC data shows that confirmed cases in the US have increased in recent weeks, and doctors across the country have reported high numbers of kids sick with RSV, as well as other illnesses.

Dr. Jesse Hackell, chair on the committee on practice and ambulatory medicine for the American Academy of Pediatrics, told The Washington Post that it was "very hard to find a bed in a children's hospital — specifically an intensive care unit bed for a kid with bad pneumonia or bad RSV because they are so full."

Dr. Juan Salazar, physician in chief of Connecticut Children's Medical Center, told The Hill RSV cases are expected to rise in fall, but they started spiking in early September and have risen exponentially since, which he hadn't seen before.

Hospitals in more than 24 states around the country, including Rhode Island, Washington, Colorado, Texas, Ohio, Louisiana, New Jersey, Massachusetts as well as the District of Columbia, told ABC News they are struggling with more pediatric cases than normal of infections other than COVID.

"We're seeing RSV infections going rampant all throughout the country," Mora, a volunteer medical spokesperson for the American Lung Association, told CNN.

Seek medical help if your child is having difficulty breathing or seems dehydrated

According to the CDC, early symptoms of RSV include: a runny nose, a cough, which may progress to wheezing, and decreased appetite.

Infants younger than 6 months may have one symptom like: irritability, decreased activity, decreased appetite, or pauses while breathing. RSV may not always cause a fever, according to the CDC.

Doctors told CNN that parents should seek medical attention if a child has any signs of labored breathing or dehydration including: breathing harder or faster, the belly moving up and down, nasal flaring, and diapers that are less wet than usual.

Infants who are premature, aged six months and younger, have birth lung or heart defects, or neuromuscular disorders that make it difficult to clear secretions are most at risk of getting sick, according to the CDC. Most kids younger than 2 years of age will catch it without getting seriously unwell.

Adults with compromised immune systems and older adults, particularly those with underlying heart or lung diseases, are also at higher risk of getting seriously ill from RSV.

RSV can spread when an infected person coughs or sneezes

A person can catch RSV when virus droplets from an infected person's cough or sneeze gets into their eyes, nose, or mouth.

Adults can catch it from kids, for example from kissing their face

Dr. Elizabeth Mack, division chief of Pediatric Critical Care at the MUSC Children's Health, said in a press release that babies often get RSV from someone in the household: "It's common that the older sibling goes to day care, went to the store, went to a party, came home, had a runny nose and then the infant got really sick."

Covering your nose and mouth when you sneeze can help prevent RSV from spreading

People can help to prevent RSV by: covering coughs and sneezes with a tissue or a sleeve, and regularly washing hands for at least 20 seconds.

Mack said that it was a "good idea" to wash your hands before interacting with a newborn, "regardless of whether you're symptomatic or have been around anybody who's sick."

"If somebody's sick, avoid close contact, avoid sharing utensils or food. Frequently touched surfaces should be cleaned if somebody in the household is sick," she said.

Parents can treat RSV at home with pain killers

There is no specific treatment for RSV. For many, it is a mild illness that can be treated at home. Parents can give their kids non-aspirin pain killers, like ibuprofen, ensure they drink enough, and speak with a healthcare provider before using non-prescription cold remedies, according to the CDC.

Babies under the age of 6 months or older people may need hospital treatment if they become dehydrated or have trouble breathing.

In severe cases, a patient may need to be given oxygen, a breathing tube, or be put on a ventilator to help them breathe, which usually lasts a few days, the CDC website states.

There isn't yet a widely available vaccine for RSV, but scientists are working on it.

"The unfortunate thing is that there is a vaccine against RSV, but it's only available to babies with high-risk conditions. Vaccinations begin in October, but the surge hit early," Mack said.