Just how bad a flu season are we having? Without a crystal ball, it’s impossible to predict the final toll. But just about any way you crunch the numbers, the prognosis is grim.
“Most people with influenza are being infected with the H3N2 influenza virus. And in seasons where H3N2 is the main cause of influenza, we see more cases, more visits to the doctor, more hospitalizations, and more deaths, especially among older people,” said Daniel B. Jernigan, MD, MPH, Director of the Influenza Division at the Centers for Disease Control and Prevention.
The rate of hospitalizations—41.9 per 100,000 for the week ending January 20—resembles that of the 2014–2015 flu season, which put an estimated 710,000 flu patients in the hospital, Dr. Jernigan said at a CDC briefing. An estimated 34 million people came down with the flu in that season; about 16 million had to visit a doctor’s office or emergency room.
In years where H3N2 dominates, the death toll has tended to reach about 56,000. Deaths certificates that list pneumonia and influenza rose sharply to 9.1% for the week ending January 20 and have been elevated for three consecutive weeks; the CDC fears that the rate may not have peaked. While no total is available for deaths overall this flu season, the agency does track pediatric mortality. Seven more pediatric deaths were reported during the week, bringing the seasonal total to 37 (with H1N1 accounting for 65% of the deaths blamed on influenza A subtypes). By the end of the 2014–2015 season, pediatric mortality reached 148.
Of course, no one can forecast the eventual outcome. “I mean, these numbers can change,” Dr. Jernigan said. “We may go above the 2014–15 season, and so I think it’s a little hard to make some of those comparisons.”
This flu season is challenging the marks set by a couple of other bad flu seasons, he noted. “From an activity standpoint,” Dr. Jernigan said, “we’re seeing the most influenza-like illness activity since 2009,” the year of the H1N1 pandemic. The number of visits to the doctor related to the flu reached 6.6% in the week ending January 20, the highest level since that pandemic year.
Based on past years, Dr. Jernigan estimated flu season is roughly half over and still worsening, but it may have peaked in some parts of the country, notably the West Coast.
The flu season has been unusual in several ways, he said.
“The first is that flu activity became widespread within almost all states and jurisdictions at the same time,” he said. “The second is that flu activity has now stayed at the same level for three weeks in a row, with 49 states reporting widespread activity, each week, for three weeks.” More commonly, different areas of the country “light up” at different times.
Another unusual feature: People ages 50 to 64 are the second-most-impacted age group after those older than 65. “These are folks that are at the peak of their careers a lot of times,” Dr. Jernigan said. “They are managing a lot of the businesses and so them missing [work] is something that can impact not only them and their families, but also those that are in the businesses that they work for.”
While Dr. Jernigan was hesitant about making predictions, he and CDC Director Brenda Fitzgerald were sure about one thing: it’s not too late to get a flu shot. Dr. Jernigan also noted that people at risk for flu complications—the very young, the very old, pregnant women, and those with underlying illnesses—should seek treatment if they experience flu symptoms.
Source: CDC; January 26, 2018.