(CNN) — Dr. Mandy Cohen, director of the US Centers for Disease Control and Prevention, updated a congressional subcommittee Thursday about cases of respiratory illness in the US due to three viruses: flu, the coronavirus and respiratory syncytial virus, or RSV.

“RSV season is in full swing,” Cohen told the House Energy and Commerce Subcommittee on Oversight and Investigations.

“Flu season is just beginning across most of the country, though accelerating fast, and while we’re seeing relatively low levels of Covid, Covid is still the primary cause of new respiratory hospitalizations and deaths, with about 15,000 hospitalizations and about 1,000 deaths every single week,” she said.

“We are seeing a lot of RSV, particularly in the southern part of the country, so we’re near peak is what I would say for RSV,” Cohen said.

“We are also at the beginning of flu season,” she said. “We’re actually having a pretty, what I would say, typical flu season. We do expect to see a lot more flu cases over the course of December and January.”

Covid is also rising again and continues to be the biggest threat of the three, she said.

“Covid is still the respiratory virus that is putting the most number of folks in the hospital and taking their lives,” she said.

Cohen added that it remains important for Americans to get vaccinated, since there are now vaccines against all three of these respiratory illnesses. Should a person get sick, it’s also critical to be tested and get treatment, as most antiviral drugs are most effective when given early in an infection.

More than a third of adults and children have gotten their flu shot this year, according to the latest data from the CDC. But only about 16% of adults and 6% of children have gotten the new Covid-19 vaccine, rates that the CDC has said are lower than it would like to see. About 15% of older adults 60 and up have gotten the new RSV vaccine.

Respiratory virus activity is especially high in the Southern and Western US. Warren County in Ohio said this week that it’s experiencing an “outbreak” of pediatric pneumonia cases, with a large uptick in the number at one time. The pathogens involved include adenovirus, Streptococcus pnuemoniae and Mycoplasma pneumoniae, bacteria that have been linked to a rising number of respiratory infections in China. Mycoplasma commonly causes mild respiratory infections, typically in crowded settings like schools, college residence halls and long

Respiratory virus season is especially affecting children. In the week ending November 18, more than 10% of doctor’s visits among children younger than 5 in the US were for influenza-like illnesses – about three times higher than the average for all ages and well above the national baseline, according to data from the US Centers for Disease Control and Prevention.

Pediatric hospital beds are filling up, too. About three-quarters of pediatric hospital beds are in use nationwide, federal data shows, and capacity hasn’t been this strained since mid-December 2022.

Hospitalizations for respiratory viruses – including Covid-19, flu and RSV – have been on the rise for months. Although Covid-19 represents the vast majority of respiratory virus hospitalizations overall, RSV is the most common culprit among children, with weekly admission rates rising 69% since the first week of October.