Officials say that this flu season is shaping up to be one of the worst in recent years.
The rate of flu hospitalizations — the number of people hospitalized with influenza per 100,000 — rose sharply last week compared with the previous week. In mid-January it was 22.7 per 100,000 people; earlier that month, the rate was 13.7.

At the peak of the 2014-15 season, one of the two most severe seasons in the last 15 years or so, 29.9 people out of every 100,000 were hospitalized with the flu.

The most recent data suggests the season may be peaking right now, according to the director of Centers for Disease Control and Prevention (“CDC”), Dr. Brenda Fitzgerald. But she warned that many more people will be infected before the season is over.

There’s a difference between an active flu season — when a large number of people get sick — and a severe season, when the numbers of people hospitalized for flu or who die from the infection are unusually high. It can be hard to tell in real-time where a flu season will fall on the severity scale, because sometimes reports of influenza hospitalizations and deaths — especially deaths among children — lag.

That said, this year is starting to look like a severe season, and may be more severe than last year, said Dr. Dan Jernigan, head of the CDC’s influenza division.

The Influenza A virus H3N2 has caused the majority of the illnesses in most parts of the United States this year. But recently, there’s been an uptick in activity by another Influenza A virus, H1N1, Jernigan said. In addition, Jernigan warned that even if the season appears to have peaked, flu viruses will circulate for weeks to come and people should continue to take precautions against getting infected.

Jernigan said that people over the age of 65 are being hospitalized for flu this season more than any other population. People age 50 to 64 are also being hospitalized in high numbers.

The flu often hits the ends of the age spectrum more than the middle, and that’s the case this year as well. The CDC reported 7 more children have died from the flu, bringing the season total to 20 as of January. While tragic, that number is low in comparison with other years — 110 last year, 92 in 2015-2016. But if other seasons are a gauge, that grim tally may continue to rise in the coming weeks.

Officials feared that the flu vaccine would not work particularly well this season, but it appears to be faring slightly better than expected.

Preliminary testing by the CDC suggests the vaccine is probably more protective than it was in Australia during its 2017 winter. The Australian interim estimate suggested the H3N2 component of the vaccine, which was the main virus there during their most recent winter, was only about 10 percent effective. That means if 100 people got the flu shot and all were exposed to H3N2 viruses, only 10 would have been protected.