What’s behind the early surge in RSV and flu — and what’s to come.

It’s not just you or your kids: Cold and flu season is off to a particularly nasty start across the United States. With the country stepping down from the pandemic footing of the past few years, the various viruses that cause coughs, runny noses, and sore throats are now on the rebound. Cases of influenza and respiratory syncytial virus (RSV), a common respiratory bug that can occasionally turn serious for infants and older adults, had been held down in 2020 and 2021 because people were wearing masks and taking other precautions to avoid Covid-19. But almost all official pandemic policies have lapsed, most Americans have returned to some or all of their pre-pandemic activities, and immunity to other common viruses may have waned after two years of largely avoiding them.

That has brought RSV in particular roaring back; the flu is showing signs of an early surge as well. In 2020, the United States as a whole was reporting just a handful of confirmed RSV cases in late October; in 2021, about 400. In 2022, the official number is about 600. Those numbers are much lower than the actual number of cases, because an RSV diagnosis is not typically confirmed via a laboratory test. But they show a clear trend.

Flu is also off to a fast start, particularly in the South. The percentage of outpatient visits that are for respiratory illness, one of the Centers for Disease Control and Prevention’s measures of flu activity, is already well above where it was at this time in the past five years. Doctors on the ground also say that they are seeing meaningfully more cases of RSV, flu, and other similar pathogens (such as adenoviruses, parainfluenza, croup, etc.) than they typically would this early in the cold-weather season.

For hospitals that have spent the past two years struggling to maintain capacity in the face of surging Covid-19 cases, this year has not brought any relief. The opposite, in fact.

“We are very busy,” Kristina Bryant, an epidemiologist at Norton Children’s Hospital in Louisville, told me. “It’s different this year. … It’s not even Halloween, and many children’s hospitals are operating at or above capacity.”

Bryant’s hospital is already contemplating spilling over into beds in the adult hospital across the street, which is connected by a pedestrian walkway. She said she’s spoken to peers in other hospitals that have already put their emergency command structures into place. Connecticut Children’s Hospital in Hartford has reportedly held talks with the Federal Emergency Management Agency and the National Guard about setting up a tent outside their building for overflow beds.

Some experts in infectious diseases have even adopted a moniker for the conflation of influenza, RSV, and Covid-19 that is already threatening hospital capacity in some parts of the United States: the “tri-demic.”

“We used to worry about a twin-demic. Now some people are worried about a tri-demic: influenza, Covid, and RSV,” William Schaffner, a Vanderbilt University professor and medical director of the National Foundation for Infectious Diseases, told me. “Although we worried about this in the past few seasons, people are really anticipating this may be the one where these viruses really gang up on us and together may strain the health care system.”

The next few months are expected to be rough, with different viruses becoming dominant at different times. Hospitals may continue to be stretched thin. The severity of any winter Covid-19 surge and the possibility of a second wave of flu later in the season are two X-factors that will dictate how bad the situation ultimately becomes.

But the experts I spoke to offered a small glimmer of hope: This is — probably — not the new normal. The US is suffering a shock after the past two years. The population is more vulnerable to various respiratory illnesses now, but it won’t stay that vulnerable forever. People will get sick and develop immunity, and that will put constraints back on these viruses.

Several of them said they expected a year, maybe two, of such unusual early and severe cold-and-flu seasons, followed by a return to relative normal. That progress could be sped along by the development of pan-coronavirus and RSV vaccines.

“I anticipate that as people get infected with these things again, it will settle down to what was around before the Covid pandemic,” said Richard Webby, an influenza expert at St. Jude Children’s Research Hospital in Tennessee.

Why RSV and influenza are surging unusually early this year

Covid-19 has thrown the viral ecosystem out of whack. Other viruses have been behaving strangely for the past few years. Bryant said her hospital saw an unusual amount of enterovirus d68, which generally causes cold-like symptoms but in rare cases can lead to limb weakness similar to polio, over the summer.

RSV usually shows up in midwinter, but the hospital also saw an early, ferocious spike in RSV cases in August and now, she said, their case volume is substantially higher than they have seen in years.

“Before the pandemic, we could predict when we were going to have RSV cases,” said Bryant, who also works on infectious disease issues for the American Academy of Pediatrics. “What has happened this year is it’s come early. … The pandemic has created disruptions in previously pretty predictable seasonal patterns.”

RSV generally starts as a runny nose or a cough. For a small number of children, it may develop into pneumonia or bronchitis, which can require hospitalization. As with Covid, which is also typically milder in children, the sheer number of infections means hospitals can be overwhelmed even if only a small share of those cases require kids to be admitted to the hospital.

The flu also started about a month earlier than usual, Schaffner said, particularly in the southern United States. It’s been following the pattern seen in the Southern Hemisphere this summer (which is winter in that part of the world), when countries including Australia and Chile saw early and busy flu seasons.

So what explains the early surge? From a biological perspective, these viruses are finding more susceptible hosts in the population. The reasons flu and RSV typically thrive in the winter are that the humidity is lower, temperatures are down, and people are more likely to crowd together indoors.

After the past two years, people have less robust immunity, or perhaps no immunity at all, making it easier for the virus to spread outside of those ideal conditions.

Every child will catch RSV multiple times, most before they turn 2, and eventually build up immunity to it. But the problem right now is a lot of kids, even 3- or 4-year-olds, have no existing immunity after two years of mitigation measures and are getting infected for the first time.

“The virus has an even more abundant playing field in which to work,” Schaffner told me. “There are many more susceptible [people] that this virus can infect for the first or second time and cause illness.”

Kids especially play a critical role in the spread of disease — as Schaffner said, “Children are thought to have the distribution franchise for the influenza virus.”

First, they spread it among themselves. And, because once infected they shed much more virus than adults and for a longer period of time, they are very efficient at spreading the virus to other people they encounter.

“They become vectors. They become little transmitters. They come home and give it to their parents, grandparents, Aunt Suzi, the neighbors,” Schaffner said. “With kids in school, with people traveling, visiting friends and relatives, doing that with enthusiasm, returning to a new normal activity, it’s setting us up for the spread of these respiratory viruses.”

Meanwhile, we are still awaiting the expected Covid-19 winter surge. Case numbers appear to be in a bit of a lull right now — though the rise of at-home testing makes official data much more difficult to follow — but given the pattern of the past two years, experts expect an increase before long. It shouldn’t get as bad as it did in 2020 or 2021, Schaffner said. But it will still add strain to the health system.

Why a “tri-demic” will — hopefully — not be the new normal

So the next few months may be rough. A second surge of flu activity in the new year, if another strain emerges and becomes dominant, would make it worse. But the lingering question is whether this is a short-term shock to the system after the pandemic or the start of a new normal.

The unpredictability of the past two years should disabuse us of being too confident about the future. But the experts I spoke to thought that the former was more likely. This cold-and-flu season will be nasty. Next year may be as well. But, eventually, these viruses will start to settle into their old pattern.

“I’ve been thinking of this as a transition year, back to the new normal. Or maybe a transitional two years,” Schaffner said. “The viruses are working their way back to a more normal activity.”

As more people get infected and build their immunity back up (or up for the first time, in the case of kids), the viruses will find it harder to spread outside of their usual sweet spot when the weather is cold and people stay inside, Webby said. We saw the same life cycle with H1N1 during and after the 2009 outbreak. At first, that virus would emerge at unusual times outside of flu season. But after a couple of years, as people gained immunity, it became more predictable.

“It forces the virus to survive only in its sweet spot for transmission, which happens to be winter,” Webby said.

New vaccines could also help soften the burden of RSV in the future. The pharmaceutical company GlaxoSmithKline released clinical trial results recently showing a large reduction in severe disease for older adults who were given an RSV vaccine that the company has developed. Development of an RSV vaccine for children had been stagnant, but a recent uptick in R&D signals a possibility of progress in the coming years.

We already have effective vaccines for flu and Covid-19, too. They substantially reduce the likelihood of severe illness and death. The challenge is getting people to take them. Few Americans have gotten the new omicron-targeted Covid-19 vaccine, and people’s intentions about getting the flu vaccine have also been lagging.

“We’re concerned the population is so Covid and vaccine fatigued that it’s not taking advantage of these vaccines,” Schaffner said. “I think there are still many people who say ‘I’ve had enough of this.’ The interventions we have are at the moment not being optimally utilized.”

Biology should help make cold and flu season in the years to come more tolerable. We also have the tools to lighten the burden even more — not only the vaccines, but washing hands, wearing masks, staying home when sick — if only we avail ourselves of them.

By Dylan Scott

Source: Vox Media

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