Flu reaches highest level in the U.S. in 25 years

Doctor visits for flu symptoms have reached their highest level since the 1997-98 flu season, new CDC data show. (SimpleImages/Moment RF/Getty Images via CNN Newsource)

Flu continues to bring misery across the U.S., with all but four states showing high or very high levels of activity as a new virus strain called subclade K continues to spread.

By another measure – visits to the doctor for fever plus a cough or sore throat, which are common flu symptoms – the US is at its highest level of respiratory illness since at least the 1997-98 flu season, according to data published Monday by the U.S. Centers for Disease Control and Prevention.

“This is definitely a banner year,” said Dr. Caitlin Rivers, an epidemiologist and senior scholar at Johns Hopkins Center for Health Security. “It’s the worst we’ve had in at least 20 years. We’re seeing a majority of the country is experiencing very high levels of activity, and we’re still in the thick of it.”

It’s striking to see such an intense season coming off last year’s bad flu season, she noted, as bad years don’t typically occur back to back.

Nationally, about 8.2 per cent of doctor visits were for flu-like symptoms during the last week of the year. At the same point last season, which was also brisk, that number was 6.7 per cent.

In Massachusetts, which is reporting very high levels of flu activity, health officials urged people to get vaccinated.

“This is a moment for clarity, urgency, and action,” Public Health Commissioner Dr. Robbie Goldstein said in a news release. “These viruses are serious, dangerous, and life-threatening. We are seeing children who are seriously ill, families grieving devastating losses, and hospitals under capacity strain.

“There is a simple, effective, and available way to address these concerns: vaccines,” he added. “They can prevent serious illness and hospitalization. And they save lives. If you have not yet been vaccinated against flu or COVID-19 this season, now is the time. It is not too late. Choosing vaccination is choosing to protect yourself, your family, your friends, your colleagues, and your community.”

Nearly all U.S. states were at high or very high levels of flu activity in the latest data. Montana and Vermont reported low levels of activity, while South Dakota and West Virginia reported moderate levels. Nevada didn’t report flu data this week but showed high levels of flu activity in last week’s report.

In terms of severity – how many people have been hospitalized by the flu – this season is not a standout yet. The cumulative hospitalization rate is the third highest by this point in the season since 2010-11, but that could change as more people are infected.

“In the next 48 hours, if you haven’t been vaccinated, get vaccinated. Don’t wait,” said Dr. Michael Osterholm who directs the Center for Infectious Disease Research and Policy at the University of Minnesota. “You know, you may still be able to protect yourself from the the last parts of the seasonal epidemic, but you know, it takes us, seven to 10 days to develop some immunity relative to the vaccine, and so you don’t have a lot of time to waste,” he added.

The CDC estimates that at least 11 million people have had the flu this season, 120,000 have been hospitalized with it and 5,000 people have died.

The agency also received another report of a child’s death, bringing the total number of children who’ve died of influenza this season to nine.

Flu vaccinations have been dropping in children, from a high of 53 per cent over the 2019-20 flu season to 42 per cent at the same point this season.

The new flu data came the same day the U.S. Department of Health and Human services announced a plan to modify the childhood vaccine schedule. The changes would recommend that kids get flu vaccines after a consultation with a health care provider, a provision called shared clinical decision-making, which could make the shots harder for people to access.

“To back off on a flu recommendation in the midst of a pretty severe flu year seems to me to be pretty tone-deaf, and that’s coming off an influenza year where we had the most childhood deaths from influenza in many years,” said Dr. Sean O’Leary, chair of the American Academy of Pediatrics’ Committee on Infectious Diseases.

Shots are also down in adults, from nearly 61 million in 2019-20 to roughly 48 million this year, CDC data shows.

Rivers said she didn’t think the lagging vaccination rates were playing a role in the high volume of cases this year.

“The vaccine is not really expected to protect against infection and therefore transmission. It’s really just about preventing severe illness,” she said.

Instead, she says, the new flu strain – subclade K, which represents most viruses analyzed by labs – seems to be the reason for the intensity.

She said that strain is just different enough from the flu viruses people have been exposed to in the past to get around our immune defenses.

Subclade K began to spread after strains were chosen for this year’s flu shots, which means the vaccines probably offer only partial protection against it.

“I think that this virus, like we saw in Australia and Japan and to some degree in the United Kingdom, has some legs to it,” Osterholm said. “I think you’re going to continue to see activity in communities for at least another three to four weeks of some real, substantial nature.”

By Brenda Goodman, CNN

CNN’s Jen Christensen contributed to this report.