Not since the 2009 H1N1 swine flu pandemic has there been so much flu, a metric the CDC uses to assess the severity of a season based on laboratory-confirmed cases, doctor visits, hospitalizations and deaths.
“It’s unusual, but we’re coming off an unusual Covid pandemic that has really affected influenza and other respiratory viruses that are circulating,” said epidemiologist Lynnette Brammer, head of the CDC’s Domestic Influenza Surveillance Team.
Activity is high in the southern and southeastern United States and is beginning to move up the Atlantic coast.
CDC uses a variety of measures to track the flu, including estimating the percentage of physician visits for flu-like illnesses. But the laboratory data leaves no doubt that similar symptoms may include people seeking treatment for covid-19 or RSV, another respiratory virus with similar symptoms.
“The data is ominous,” said William Schaffner. is the medical director of the nonprofit National Foundation for Infectious Diseases and a professor of infectious diseases at Vanderbilt University School of Medicine. “Influenza is not only early, but it looks very bad. This is not just a preview of the attractions to come. We have already started watching this movie. I would call it a scary movie.
Adding to his concerns, he said, the flu shot is usually too late at this point in the season. About 128 million flu vaccine doses have been distributed so far, compared with 139 million at this time last year and 154 million the year before that, according to the CDC.
“It makes me doubly anxious.” Schaffner said The flu burden “certainly looks like the start of what could be the worst flu season in 13 years.”
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This season’s flu cases are already one-eighth of last season’s total estimated 8 to 13 million cases.
The latest flu data comes as the nation’s strained public health system grapples with multiple viral threats. As the country moves into colder weather and more people gather indoors, the number of coronavirus cases is expected to rise. New covid-19 subtypes that are more capable of evading immune defenses now account for 27 percent of cases, up from 17 percent a week ago. Children’s hospitals are overflowing with a record number of children infected with RSV.
The flu vaccine’s effectiveness in preventing a doctor’s visit, hospitalization or death varies from year to year, and in past years has hovered between 40 and 60 percent, according to the CDC. But Brammer and others say this season’s vaccine is better suited to circulating strains. It gives “a little ray” to what could be a dark winter, Schaffner said.
Nationally, the dominant virus — a particularly nasty strain, H3N2 — is causing the worst outbreaks of the two Two types of influenza A virus and influenza B virus circulate in humans. Seasons in which H3N2 dominates typically cause more complications, especially for 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 generated by the virus increases the rate of heart attacks, wreaking havoc for another four to six weeks in middle-aged and older people. And strokes, Schaffner said.
Influenza has not been a serious problem in the past two years, experts and health officials have said, because of masks, social distancing and other measures people have taken to protect themselves against COVID-19.
A flu season is officially considered underway after several consecutive weeks of flu activity in several surveillance systems, including a significant percentage of physician office visits for flu-like illnesses, according to health officials. Those doctor visits had increased for three consecutive weeks as of Oct. 22, a month earlier than in previous periods, the CDC’s Brammer said.
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Flu is difficult to predict. It is difficult to know how long the season will last, how severe it may be, and whether different parts of the country may experience different levels of respiratory disease at different times. Last season, flu activity peaked in January, “then dropped like a rock, smoldering below the epidemic threshold beyond March into April, May and June,” Schaffner said. That “long smoking tail was very unusual.”
“A quick start doesn’t always mean drastic,” Brammer said.
In the Southern Hemisphere, the flu season has also varied greatly, Brammer said. In Australia, she said, there was a “really sharp, very rapid rise and then a very quick fall”. In Argentina, peak flu activity occurred during that country’s summer.
“Things are not back to normal,” Brammer said.
According to a CDC report this week, Chile got ahead of its worst flu season, which started months earlier than a normal season, by rapidly vaccinating 88 percent of its high-risk population before peak influenza activity. The flu vaccine used in Chile, which included a match for the dominant H3N2 virus, was about 50 percent effective in preventing hospitalizations. The vaccine used in the Northern Hemisphere contains the same virus composition as the Southern Hemisphere vaccine, so experts hope the formulation will be equally effective in preventing severe influenza illness.
The latest CDC data shows that 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. In the Houston Methodist Hospital system, 20 laboratory-confirmed influenza cases rose to 975 as of Oct. 20, up from 561 a week earlier, officials said.
Officials were bracing for a stronger flu season this fall and winter as many people have abandoned Covid-19 precautions and are reluctant to get vaccinated.
“This was something we expected because we are a hub and a lot of people travel here,” said Cesar Arias, the hospital system’s chief of infectious diseases. But, he said, “I didn’t expect to see that much [flu] That was before.”
Conversations about flu shots are intertwined with ambivalence about coronavirus vaccines, Arias said. Conversations in Texas, “As you can imagine, [are] Stronger and at least more vocal,” he said. “We’re struggling with that, trying to get the message across to get vaccinated.”
People must get a new flu shot each year to be protected, and it takes up to two weeks for protection to kick in and for the vaccine to take effect. The flu is contagious before symptoms begin. The CDC recommends that everyone age 6 and older get a flu shot by the end of October.