15 states seeing 'high' or 'very high' levels of respiratory illness: CDC

Respiratory illness activity is elevated or increasing across most areas of the United States, according to data from the Centers for Disease Control and Prevention (CDC).

In total, 15 states plus New York City are experiencing "high" or "very high" levels of respiratory illness activity, defined as people going to the doctor with symptoms from any respiratory disease including flu, COVID, RSV and the common cold.

COVID-19 and flu hospitalizations appear to be trending upward while RSV hospitalizations appear to be to be stable, the data shows.

Weekly COVID-19 hospitalizations have reached levels not seen since the end of February with 22,513 recorded the week ending Dec. 2. However, they remain lower than rates seen at the same time last year.

COVID-19 hospitalization rates are elevated for infants and young children and highest among senior citizens, meaning serious illness is mainly affecting the oldest and youngest Americans.

COVID-19 deaths are currently stable, but experts have previously warned that because deaths are a lagging indicator, the number of fatalities due to the virus could rise over the next few weeks.

The CDC is actively tracking a rising variant known as JN.1, a descendant of the BA.2.86 omicron subvariant, according to an update posted by the federal agency on Friday.

Currently, JN.1 makes up an estimated 21% of cases. While some scientists believe it may be more transmissible due to its continued growth, there is currently no evidence it is more severe than previous variants.

Meanwhile, flu activity continues to increase with the southeast and south-central areas of the U.S. reporting the highest levels of activity, according to the CDC. Modeling from the federal health agency estimates flu infections are growing or likely growing in 34 states, declining or likely decline in one state, and stable or uncertain in four states.

Flu hospitalizations are also increasing, yet the number of new admissions remains low at 5,753 admitted the week ending Dec. 2, an increase from 4,268 the previous week, data shows.

The CDC estimates that there have been at least 2.6 million illnesses, 26,000 hospitalizations, and 1,600 deaths from flu so far this season.

Meanwhile, RSV weekly hospitalization rates have very slightly declined to 2.4 per 100,000 for the week ending Dec. 2 from 2.5 per 100,000 the previous week. RSV hospitalizations remain elevated among young children under 4 and are increasing in older adults over 65.

It comes as the White House urged the makers of RSV immunizations this week that protect infants and toddlers to speed up production to increase access.

The monoclonal antibody shots, which are a bit different than a vaccine but still provide protection, have been in high demand and short supply.

Meanwhile, hospitals in some areas of the U.S., such as in Washington state, are reinstating masking.

At Northwest Healthcare Response Network in western Washington, officials said RSV cases hit a threshold required updating rules on masking throughout its partner hospitals, according to local ABC News affiliate KOMO News.

Additionally, Mary Bridge Children's Hospital in Tacoma reached the RSV threshold earlier this week and the flu threshold on Thursday, officials told KOMO News.

When it comes to vaccinations, data showed much higher uptake for the flu vaccine than for the COVID-19 or RSV vaccine.

As of Dec. 2, 40.8% of adults and 41.6% of children have received the annual flu shot, CDC data shows. Comparatively, 17.2% of adults and 7.7% of children have received the updated COVID-19 vaccine and just 15.9% of adults aged 60 and older have received the new RSV vaccine.

Dr. Philip Huang, director of Dallas County Health and Human Services, advised people to follow the same mitigation measures they have for previous seasons.

"Everything that we're hearing about it is not any new virus or new pathogen, it is the common things that we see every season that perhaps coming together," he said. "The preventive things are all the same, you know, stay home if you're sick, wash your hands, cough into your sleeve, don't rub your eyes, nose and mouth, get up to date on the vaccinations."

Huang said he might advise wearing a mask if you're around someone who is at a higher risk of severe illness or if you're in a crowded area with poor ventilation.