"By that measure we're about halfway there for this season," Jernigan explained. "That means we have several more weeks of flu to go."

Flu activity has been elevated for nine consecutive weeks this season, Jernigan told reporters Friday. Typically, it lasts for about 16 weeks, with the longest being 20, he said.

"While flu activity is beginning to go down in some parts of the country, it remains high for most of the U.S., with some areas still rising," said Dr. Dan Jernigan, director of the Influenza Division at the Centers for Disease Control and Prevention's National Center for Immunization and Respiratory Diseases.

Flu activity in the U.S. remains high, and there are still several weeks to go, public health officials said Friday, noting overall this season most resembles 2014-2015, considered highly severe.

Two things are different about this flu season, Jernigan said. First, most of the country is experiencing widespread flu simultaneously. Second, the next most-affected group after those older than 65 are baby boomers: people between ages 50 and 64. Normally it's kids under 4 that see the second-highest level of hospitalizations from flu, Jernigan said.

"Baby boomers have higher rates than their grandchildren right now," he said.

That may be because of the strains in circulation, he explained. While most of this year's severity is due to the predominant H3N2 strain, a particularly nasty one not well protected by the flu shot, the H1N1 strain is also sending baby boomers to the hospital.

"Those folks really would benefit from having higher vaccination coverage," Jernigan said. "These are folks at the peak of their careers, managing businesses" — so missing work, as public health officials universally recommend people do when they have flu-like symptoms — affects not just them but those in the businesses they work for.

Hospitalization rates are similar to those in the 2014-2015 season, which saw a total of 710,000, Jernigan said. By a measure of influenza-like illness measured by outpatient visits, this season is the worst since the 2009 swine flu pandemic.

The CDC reported an additional seven deaths among children for the week ending Jan. 20, bringing the total for the season to 37. Jernigan said, though, that those numbers may underestimate reality.

"Sometimes, tragically, children will die outside of the hospital, and you have to have a coroner report or medical exam report" for the death to reach the CDC, Jernigan said. "It may even be twice the number we have."

Jernigan said there are spot shortages of some antiviral drugs for flu, specifically oseltamivir suspension and generic oseltamivir capsules. Oseltamivir is the generic name for Tamiflu.

"This is happening in areas where there is high influenza activity," Jernigan told reporters. "The CDC is working to address any gaps in the market."

The CDC still recommends people get a flu shot if they haven't already, as it could still provide protection in the weeks left in flu season. Jernigan suggested calling pharmacies or doctors' offices in advance to check on availability of shots or antiviral medicines.