The ferocious start to this flu season has given way to record-breaking transmission levels — and huge pressure on the US health system.
In the week ending Nov. 26, more than 34,000 positive flu tests were reported to the Centers for Disease Control and Prevention (CDC) from laboratories across the U.S., as shown in the orange line on the chart below. That’s more positive flu tests than reported in a single week during a recorded flu season, dating back to 1997.
The trajectory dwarfs the past six flu seasons, including the relatively poor 2019-2020 season that immediately preceded the onset of the Covid-19 pandemic (shown in the black line).
Part of this surge in cases is related to more people being tested for the flu than in previous years. In the month of November, about twice as many flu tests were conducted in clinical labs across the country as during the same period last year (about 540,000 versus 265,000). More testing means more things are picked up.
However, there are confirmatory warning signs that this is a really bad season. Hospital admissions for flu are unpopular and are increasing rapidly. In a news conference Monday, CDC Director Rochelle Walensky said there have already been 78,000 flu hospitalizations this season, or nearly 17 in every 100,000 Americans. That’s “the highest we’ve seen in a decade at this time of year,” she said. Consistent with past trends, the highest hospital admissions are in adults aged 65 and over.
What makes these high hospitalization rates particularly concerning is their overlap with spikes in other viruses, making many people sick enough to require hospitalization. One is RSV, which has been packing children’s hospitals for more than six weeks. And while Walensky noted there were signs that RSV transmission was slowing in parts of the country, Covid-19 hospitalizations recently started to rise.
A major reason for the convergence of these viral waves: low population-wide levels of antibodies to many common colds and flus. Pandemic-era preventative measures delayed the first infections in many children – which, while good for the health of individual children, meant that a larger number than usual were susceptible to serious infections when those preventative measures were lifted. (More on the concept of “immunity guilt” and how it can be dangerously misinterpreted here.)
We can still flatten the flu season curve
Americans aren’t doing all they can to protect themselves from respiratory viruses, either: Only a quarter of adults and 40 percent of children have received a flu shot this season, and 15 percent of adults eligible for an updated Covid-19 19 booster dose got one .
That means important missed opportunities for prevention: This year’s flu shot is expected to be particularly effective, Walensky noted, because it’s a close match to circulating flu strains, which vary from year to year. However, it only works if people get it.
In addition, many of the preventive measures that have proven effective during the Covid-19 pandemic remain largely unused, although they would also be useful in preventing the spread of other respiratory illnesses. There has not been much push to implement high levels of ventilation and filtration in US buildings. Only a quarter of Americans have changed their behavior to reduce exposure to viruses. And a minority of Americans often wear masks outdoors.
Amid the flu wave, drug shortages are complicating efforts to prevent serious illness and treat bacterial infections that can follow some flu infections. In addition, the staff shortages that have increased due to the pandemic have allowed children’s hospitals to care for a huge wave of sick children with even fewer resources than before. While pediatric health care organizations have called for a national emergency declaration to support their response to this wave, none has materialized.
In the US, flu infections normally peak between December and February. It remains to be seen whether the current early flu wave will translate into an early flu spike — or instead portend a prolonged period of extraordinarily high viral transmission, with an increasing burden on healthcare workers as more people become seriously ill.
After a few punishing years, it is not clear how much more pressure the US health care system can handle.