Flu season is off to a slow start this year.
Influenza activity in the U.S. remained relatively low from October through January — so low, in fact, that the current flu season is considered not to have officially begun until the first week of February, when hospitals reported a slight increase, according to a new report from the Centers for Disease Control and Prevention.
In the last 29 years, the only other flu season to start so late was 24 years ago, during the 1987-88 flu season, the report said.
"This pattern is unusual, but not unprecedented," Dr. Joseph Bresee, chief of the epidemiology and prevention branch at the CDC, said today (Feb. 24) at a news conference about the report.
The majority of flu viruses now in circulation are similar to the ones in this year's flu vaccine, according to the CDC.
"If you haven't gotten you flu vaccine yet, get your vaccine now— it's not too late," Bresee said. Flu vaccination is recommended for t those ages 6months and older in the United States.
Bresee said the late start may, in part, be due to increases in flu vaccination rates. As of November, more people had been vaccinated compared with November 2010, Bresee said. "As vaccine coverage increases, we ought to see less disease in the United States," he said.
In addition, the viruses circulating this year are similar to those of the 2010-2011season,so there may be higher rates of immunity to the viruses this season, Bresee said. However, these two factors are probably not the sole reasons for the late start.
Researchers cannot predict when flu season will peak or how long it will last. "We can only be certain that flu is inherently unpredictable," Bresee said.
Three children have died of influenza-related illness so far this flu season. Last year, 122 died during the entire flu season.
Since October, hospitalizations for flu have been highest among those younger than 4(2.2 per 100,000 people) and older than 64 (3.2 per 100,000 people).
Flu cases have been reported in all 50 states, but as of Feb. 11, just one of them, California, had reported widespread flu activity, meaning an increase in cases in at least half the regions in the state.
So far, no resistance to the antiviral drugs oseltamivir and zanamivirhas been seen in the strains currently in circulation, the report said.
The report is published today (Feb. 24) in the CDC's Morbidity and Mortality Weekly Report.
Pass it on:T his year's flu season has only just begun, the latest start in nearly a quarter-century, CDC says.
Editor's note: This article was updated on Feb. 24 to include comments from the CDC news conference.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.