U.S. health experts are struggling to determine why flu-like illness is increasing among younger people in a change from previous seasons, while also trying to quell fears that young and healthy people are dying of the flu at a higher rate than normal.
“We’re not seeing alarming numbers of deaths and hospitalizations in otherwise healthy or normal people,” Dr. Anthony Fauci, director of the National Institutes on Allergy and Infectious Disease, told The Washington Times.
Statistics on the current flu season in the U.S. are tracking close to those of the 2014-2015 season, which also had Influenza A (H3N2) as the dominant strain of the virus. In that season, 34 million people in the U.S. contracted flu-like illness, 710,000 were hospitalized and 56,000 died.
This year, the statistics are diverging in surprising categories. People older than 65 years old still account for the highest hospitalization rate for the flu, but now people between 50 and 64 have the second-highest rate for hospitalization. Children 4 years old and younger usually have the second-highest hospitalization rate for the flu.
“For some strange reason, 50- to 64-year-olds have bumped out the kids from the second worst and the kids are the third worst,” Dr. Fauci said. “So there’s something more vulnerable about the people from 50 to 64 compared to those who are 65 and older.”
In 2014-2015, people 65 and older were hospitalized at a rate of 198.4 per 100,000; their current hospitalization rate is slightly lower, at 183 per 100,000.
This year, people between 50 and 64 are being hospitalized at a rate of 44.2 per 100,000, while the hospitalization rate for children is much lower, at 27 per 100,000.
What’s more, people between 18 and 49 account for a higher percentage of flu hospitalizations this year (14.3 percent) than in the 2014-2015 season (12.3 percent).
“We don’t know the reason, that’s point No. 1,” Dr. Fauci said. “Point No. 2, given the fact that different age cohorts sometimes have an influence on their severity on any given year, based on what they were ’imprinted’ with when they were kids is a reasonable explanation why.”
“Imprinting” theory suggests that the type of disease people are exposed to when they are children better protects them from that strain or a similar illness when they’re older.
At least 37 children have died of flu or pneumonia this season, according to the Centers for Disease Control and Prevention, and 9.1 percent of U.S. adult deaths between October and January were related to the flu.
Dr. Fauci said that stories of perfectly healthy people dying from the flu within a few days are statistical outliers and do not indicate a wider health crisis.
Flu deaths range from year to year, due to the virus’ unpredictable and changing nature, yet deaths are most likely to occur in people with underlying health issues.
Adults 65 years old and older, and children 4 years old and younger, typically are most vulnerable to infection, as are people with chronic heart disease, diabetes, obesity, pregnancy and immune system deficiencies, according to the CDC. In addition, higher rates of flu complications are found in American Indians and Alaska Natives.
A 2010 CDC report sought to quantify the average death rates over a three-decade period. Of the 22 flu seasons in which H3N2 was the predominant strain, the death rate was 2.7 times higher than the nine seasons it wasn’t.
People over 65 accounted for the highest percentage of deaths each season. Over the 30-year period examined by CDC researchers, 87.9 percent of flu-related deaths occurred in adults 65 and older. Adults 19 to 64 years old accounted for 10.6 percent of flu deaths, and people younger than 19 years old accounted for 1.5 percent of those deaths.
Health officials encourage people to get flu shots, even though the vaccine has been shown to be about only 30 perfect effective against the H3N2 strain.
The CDC estimates that 80 to 85 percent of pediatric flu-related deaths occur in children who weren’t vaccinated.
At least 40.1 percent of 50- to 64-year-olds received the flu vaccination as of early November, compared to about 57 percent for those age 65 and older.
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