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This year’s flu epidemic is sending thousands of elderly people into hospitals and has killed at least 26 children, federal health officials said Friday.

They issued a reminder to doctors to make quick use of antiviral drugs in people most at risk of serious flu complications – including the elderly, very young children, people in the hospital and patients with chronic conditions such as asthma.

"This year is shaping up to be a bad one," Centers for Disease Control and Prevention director Dr. Tom Frieden told reporters.

“Hospitalization rates are especially high among people 65 years and older,” the CDC added in a statement.

“Hospitalization rates are especially high among people 65 years and older."

It’s especially important for people to get treated for flu this year because the strain making most people sick is different from the strains included in this season’s vaccine. That means even if people were vaccinated, they might be protected against some of the flu that’s going around, but not all of it. Most of the influenza infecting people this year is a strain called H3N2, and about two-thirds of the H3N2 is a mutated variety that’s not included in the cocktail of strains in the flu shot.

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Flu usually makes the very young and the very old the sickest. Depending on the season, it kills anywhere between 4,000 and 50,000 people a year in the United States. When it’s an H3N2 strain, like this year, it hits the elderly hard.

"H3N2 is a nastier flu virus than the other flu viruses," Frieden said.

So the next best thing to having a good vaccine is taking antiviral drugs, and CDC says while there are three drugs on the market, they are not used often enough.

“All hospitalized patients and all high-risk patients (either hospitalized or outpatient) with suspected influenza should be treated as soon as possible with one of three available influenza antiviral medications,” CDC says in the advisory sent to doctors Friday.

“This should be done without waiting for confirmatory influenza testing. While antiviral drugs work best when given early, therapeutic benefit has been observed even when treatment is initiated later.”

“All hospitalized patients ... should be treated as soon as possible with one of three available influenza antiviral medications."

The three flu drugs on the market that still work against flu are oseltamivir, a pill sold under the brand name Tamiflu; zanamivir, an inhaled drug sold under the name Relenza; and peramivir, an injected drug sold under the name Rapivab.

"Treatment with anti-flu drugs is even more important than usual," Frieden said. "They work but they aren’t being used nearly enough," he added.

"If you have influenza and you get the medicine early, you may not have to be admitted to a hospital. Treatment with antivirals could even save you life."

CDC says the flu season likely has a ways to go yet – the average flu season runs for 13 weeks and the United States is about seven weeks into the season.