Mar 23, 2019 | Updated: 12:48 PM EDT

A nasty new flu is bringing new rounds of illnesses

Mar 15, 2019 04:26 PM EDT

flu vaccine

The flu season this year has peaked and health officials are now monitoring a recent wave of illnesses from a flu strain that is nastier. Flu was reported to be widespread in 48 states last week, down from 49 the week before, the Centers for Disease Control and Prevention said Friday in its latest report on this winter's flu season. The federal agency's flu forecasters think there's a 90 percent chance the flu season has peaked.

But experts also are monitoring an increase in illnesses from a kind of flu virus that tends to cause more hospitalizations and deaths, especially in the elderly. It's not unusual for several flu strains to spread around the country at the same time, but one kind usually predominates.

This season, a milder strain has been the most common cause of flu illnesses. But for the last two weeks, more illnesses have been tied to a strain that tends to cause more deaths. Last week, about 60 percent of the flu virus samples tested were the more troublesome strain, known as Type A H3N2.

Uncertainty about what kind of H3N2 will be spreading later this year recently led the World Health Organization to postpone its decision on which strains should go into the flu vaccine for next season. Last season, an estimated 80,000 Americans died of flu and its complications, the disease's highest death toll in at least four decades. In recent years, flu-related deaths have ranged from about 12,000 to 56,000, according to the CDC.

CDC officials estimate there have been somewhere around 20,000 to 30,000 flu-related deaths so far this winter. They also think there have been around 300,000 flu-related hospitalizations and around 25 million flu illnesses.

Health officials are also encouraging the public to get their flu shots. To compare, the vaccine was reported to be 36 percent effective at this time last year.

The vaccine must be reformulated each year to match the most common flu strains. This year's vaccine was designed to attack four strains: H1N1, H3N2, Influenza A, and Influenza B. The predominate strain this year has been the H1N1 virus, with the H3N2 strain popping up more in southeastern states. Because this year's shot contains these strains, those who got vaccinated are well protected.

The vaccine not only prevents the flu but reduces the duration and severity of symptoms. The CDC encourages people who haven't gotten the shot to do so. Even if you already had the flu this year, it's worth getting vaccinated.

"Flu vaccines protect against more than one strain of the flu, and just because you were infected with one strain of the flu doesn't mean you won't get a second infection with another strain that's circulating," Dr. Amesh Adalja, an infectious disease specialist at the Johns Hopkins University Center for Health Security, told Healthline. Adalja is also a spokesperson for Theraflu.

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