(CNN) — Most US states are experiencing high or very high flu activity, and levels continue to increase nationwide.
“Flu season is just getting started, so I think it’s really hard to say exactly what it’s going to look like,” Dr. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told CNN on Tuesday. “What we’re seeing right now is a very rapid escalation of cases.”
The US Centers for Disease Control and Prevention estimates that there have been at least 7,500,000 illnesses, 81,000 hospitalizations and 3,100 deaths from flu this season, according to an update published Tuesday with data through December 20. At least eight children have died from flu this season.
Among the states with the highest levels of flu activity are Colorado, Louisiana, New Jersey, New York and South Carolina, according to the CDC.
Trends are increasing across key surveillance metrics: Laboratory testing, outpatient health care visits, hospitalizations and mortality are all higher than they were in the previous weekly update from the CDC.
One surveillance system shows that flu hospitalizations have doubled; more than 19,000 people were admitted to the hospital with flu during the most recent week, up from about 9,900 the week before.
The CDC says that “severity indicators remain low at this time, but influenza activity is expected to continue for several weeks.”
Staying ahead of ‘super flu’
Influenza A(H3N2) viruses are the most commonly reported, and additional genetic testing suggests that a new flu variant — called subclade K — appears to be behind the vast majority of cases in the US. After driving high case numbers in other parts of the world, subclade K got the nickname “super flu.”
“This is a strain that’s different than what we’ve seen in previous years,” Osterholm said. He wouldn’t call it a “super strain,” he said, but “I would say it surely does challenge our previous immunity, in terms of protecting us.”
This new variant wasn’t included in this year’s flu shots because it was identified after scientists had chosen the strains to include, but the vaccines contain related strains, and globally, they seem to be working pretty well against the variant.
The CDC recommends that everyone age 6 months and older get a flu vaccine each season, but vaccination rates have been decreasing in recent years. Only about 130 million flu vaccines have been distributed this season, CDC data shows, 13 million fewer doses than at this point last year. Additional data suggests that only about 17% of children and 23% of adults had gotten their seasonal flu vaccine by the end of November.
Osterholm encourages people who haven’t been vaccinated against flu to act quickly as the virus is “wiping through” the country.
“It’s not too late to get your flu shot,” he said. “It doesn’t guarantee you won’t get flu. It doesn’t guarantee that you still won’t get sick, but it surely is a big improvement on what the otherwise outcome could be, of either being seriously ill or dying.”