Flu Season Got Off to a Slow Start. But Now It’s Widespread in Almost Half the Country

After a relatively slow start to flu season, influenza activity is now widespread in nearly half of U.S. states.

Twenty-four states and Guam were reporting widespread influenza activity — meaning the virus has spread to many parts of the state, regardless of severity — as of Dec. 29, the latest date included in the Centers for Disease Control and Prevention’s (CDC) weekly flu report. Meanwhile, 19 states and New York City were reporting high levels of influenza-like illness activity, meaning a much higher-than-average proportion of doctor’s visits could be attributed to the flu. Nationally, about 4% of outpatient appointments were related to the flu during the week ending Dec. 29.

Hospitalization rates associated with the flu remained relatively low, at 5.4 admissions per 100,000 people. Rates, however, were higher among young children and the elderly (14.5 and 11.9 hospitalizations per 100,000 people, respectively), as these populations are more susceptible to complications of the flu. Thirteen children have died from the flu so far this season.

Although flu cases are climbing, the numbers are still well behind those reported at this time last year, when the nation was in the midst of one of its most severe flu seasons on record. At this point in the 2017-2018 flu season, 46 states were reporting widespread flu activity, there were 13.7 flu hospitalizations per 100,000 people and almost 6% of doctor’s visits were related to the flu.

The severity of last year’s flu season, which killed an estimated 80,000 people, may be one of the reasons behind the slow start to the 2018-2019 season. Data suggests that more people got vaccinated earlier this year than they did last year, perhaps motivated by memories of the prior season.

The viruses circulating this year are another reason for the milder season. H3N2, the strain largely responsible for last year’s outbreak, has so far been less common than the H1N1 strain. Flu shots tend to work better against H1N1 than they do against H3N2, so higher early-season vaccination rates may mean that fewer people are getting sick. (In states where H3N2 has been circulating widely, namely in the southern half of the country, flu season has been more severe.)

With illness spreading and months of flu season left to go, experts still recommend getting a flu shot. While it’s best to get one early in the season, it’s never too late — and doing so may protect not only you, but also children, the elderly and other vulnerable populations, experts say.