The 2022 flu season started a month earlier, the severity is the highest in 13 years

Not since the 2009 H1N1 swine flu pandemic has there been such a high burden of influenza, a metric the CDC uses to gauge the severity of a season based on laboratory-confirmed cases, doctor visits, hospitalizations and deaths.

“It’s unusual, but we’re coming out of an unusual covid pandemic that really affected influenza and other circulating respiratory viruses,” said Lynnette Brammer, an epidemiologist who leads the CDC’s domestic influenza surveillance team.

Activity is high in the south and southeast of the US, and is beginning to move along the Atlantic coast.

The CDC uses a number of measures to track flu, including estimating the percentage of doctor visits due to flu-like illnesses. But given the similar symptoms that could include people seeking care for covid-19 or RSV, another respiratory virus with similar symptoms, the lab data leaves little doubt.

“The data is ominous,” said William Schaffner, medical director of the nonprofit National Foundation for Infectious Diseases and professor of infectious diseases at Vanderbilt University School of Medicine. “Not only does the flu hurt, but it looks very serious. This is not just a preview of upcoming attractions. We are already starting to watch this movie. I would call it a scary movie.”

Adding to his concern, he said, is that flu vaccine uptake is lagging behind what it usually is at this point in the season. “That makes me doubly worried,” he said. The high flu burden “certainly looks like the start of what could be the worst flu season in 13 years.”

The number of flu cases this season is already one eighth of last season’s total estimate of 8 to 13 million cases.

So far, flu vaccination rates in the United States are lower than they have been at this point in the season in recent years. About 128 million doses of flu vaccine have been distributed so far, compared with 139 million at this time last year and 154 million the year before, according to the CDC.

The latest flu data comes as the nation’s strained health care system grapples with multiple viral threats. The coronavirus Cases are expected to increase as the country enters colder weather and more people gather indoors. Children’s hospitals are filled with a record number of children infected with RSV.

The flu vaccine’s effectiveness in preventing doctor visits, hospitalizations or death is uneven from year to year, and in past years has ranged between 40 and 60 percent, according to the CDC. But Brammer and others say this season’s vaccine is well-matched to circulating strains. That offers “a little ray of sunshine” for what could be a bleak winter, Schaffner said.

Nationally, the prevailing virus — a particularly dangerous strain, H3N2 — is causing the worst outbreaks of the two influenza type A and two influenza B viruses that circulate among humans. Seasons where H3N2 dominates tend to result in the highest number of complications, especially in the very young, the elderly and people with certain chronic health conditions, experts say.

What many people don’t realize is that even after someone recovers from the flu, the inflammatory response triggered by the virus continues to wreak havoc for another four to six weeks in those who are middle-aged and older, increasing the rate of heart attacks and strokes, Schaffner said.

The flu has not been a serious problem for the past two years, experts and health officials say, because of masks, social distancing and other measures people have taken to protect themselves from Covid-19.

Health officials typically consider flu season officially underway after consecutive weeks of flu activity from several surveillance systems, including a significant percentage of doctor visits due to flu-like illnesses. Those doctor visits have increased for three straight weeks since Oct. 22, more than a month earlier than in previous seasons, the CDC’s Brammer said.

The flu is notoriously difficult to predict. It is difficult to know how long the season will last, how severe it might be, and whether different parts of the country will experience different levels of respiratory illness at different times. Last season, flu activity peaked in January, “then it dropped like a rock and then smoldered just below the epidemic threshold after March into April, May and June,” Schaffner said. That “long smoldering tail was very unusual.”

“Early start doesn’t always mean serious,” Brammer said.

In the southern hemisphere, the flu season was also vastly different, Brammer said. In Australia, there was a “really sharp, very quick increase and then a very quick decline”, she said. In Argentina, the peak of flu activity occurred during what could be summer in that country.

“Things have not returned to a normal pattern,” Brammer said.

Chile weathered its bad flu season, which started months earlier than the usual season, by quickly vaccinating 88 percent of its high-risk population before flu activity peaked, according to CDC report this week. The flu vaccine used in Chile, which included a match to the dominant H3N2 virus, was about 50 percent effective in preventing hospitalization. The vaccine used in the northern hemisphere contains the same viral composition as the vaccine for the southern hemisphere, so experts hope that the formulation could be just as effective in preventing severe flu illnesses.

The latest CDC data shows overall respiratory disease activity is “very high” in South Carolina and Washington, DC and “high” in 11 states: Alabama, Georgia, Louisiana, Maryland, Mississippi, New Jersey, New York City, North Carolina , Tennessee , Texas and Virginia.

Texas was among the first states to see flu activity in late September. At the Houston Methodist Hospital System, the number of laboratory-confirmed flu cases rose to 975 as of Oct. 20, up from 561 the week before, officials said.

Officials have been bracing for a stronger flu season this fall and winter because so many people have abandoned covid protection measures and are reluctant to get vaccinated.

“This is something we expected because we are a hub and a lot of people travel here,” said Cesar Arias, the hospital system’s head of infectious diseases. “I didn’t expect to see so much [flu] so early.”

Arias said that flu vaccination talks have become tied to the hesitancy over the coronavirus vaccine. Conversations in Texas, “as you can imagine, [are] stronger and at least louder,” he said. “We are fighting it, trying to send a message to vaccinate.”

People need to get a new flu shot every year to be protected, and it takes up to two weeks for the protection to kick in and for the vaccine to start working. The flu is contagious before symptoms appear. The CDC recommends that everyone 6 months and older get a flu shot, ideally by the end of October.