Will flu and RSV always be this bad?

In the northern hemisphere, this year’s winter has not yet begun. But Melissa J. Sacco, a pediatric intensive care specialist at UVA Health, is already dreading what might come next.

For months, the intensive care unit where Sacco works has been crowded with children amid an early surge of respiratory infections. Across the country, viruses like RSV and influenza, which were once near record lows due to the easing of the pandemic, are now back in full force, all while COVID-19 continues to rage and the health care workforce continues to be depleted. Most nights since September, Sacco told me, her intensive care unit has been so crowded that she’s had to turn children away “or come up with creative ways to manage patients in emergency rooms or emergency departments,” where her colleagues are already overburdened and children are more easily slip through the cracks. The team has no choice: critically ill children have nowhere else to go.

Similar stories have been pouring in from all over the country for weeks. I recently spoke with a doctor in Connecticut who called this “by far the worst increase in disease I’ve seen in 20 years”; another in Maryland told me, “There were days when you couldn’t find an intensive care bed anywhere in the mid-Atlantic.” About three-quarters of the country’s pediatric hospital beds are full; some hospitals pitched tents outside emergency departments or considered calling in the National Guard to accommodate the overflow. Last week, the Children’s Hospital Association and the American Academy of Pediatrics asked the Biden administration to declare a national emergency. And experts say that the end of the crisis is not in sight. When Sacco imagines a similar wave hitting her team again next fall, “I get the feeling of burning tears at the bottom of my eyes,” she told me. “This is not sustainable.”

Experts I spoke with are mostly optimistic that these cataclysmic infection rates won’t become the fall norm. But they also still don’t fully understand the factors that led to this year’s surge, making it hard to know for sure whether we’ll be in for an encore.

One way or another, COVID has most certainly thrown off the usual year-end schedule. Respiratory viruses typically accelerate in late fall, peak in mid-to-late winter, and then subside by spring; they often work in relay, with one microbe emerging a little before the other. This year, however, nearly every pathogen arrived early, rising in overlapping waves. “Everything happens at once,” says Kathryn Edwards, a pediatrician and vaccinologist at Vanderbilt University. November is not over yet, and RSV has already sent infants to hospital, exceeding pre-pandemic norms. Influenza hospitalization rates are also the worst in more than a decade; about 30 states, plus DC and Puerto Rico, are reporting high or very high levels of the virus weeks before it typically begins its rise across the country. And the rise of rhinoviruses and enteroviruses in the country in late summer has yet to fully subside. “We just haven’t had a break,” says Asuncion Mejias, a pediatrician at Nationwide Children’s Hospital.

Previous pandemics have had similar backfires. For example, the 2009 H1N1 influenza pandemic appears to have delayed the onset of the two subsequent RSV seasons; seasonal flu also took several years to return to normal, Mejias told me. But that unstable schedule was not permanent. If next year’s virus calendar is a little more regular, Mejias said, “it will make our lives easier.”

This year, flu and RSV also took advantage of Americans’ higher-than-average vulnerability. Especially initial encounters with RSV can be rough, especially in infants, whose airways are still small; the disease eases with age as the body develops and immunity builds, leaving most children well protected in childhood. But this fall, the pool of defenseless little ones is bigger than usual. Children born just before the pandemic or during crisis phases when there were still plenty of mitigation measures in place may be experiencing influenza or RSV for the first time. And many of them were born to mothers who themselves experienced fewer infections and thus passed on fewer antibodies to their babies during pregnancy or breastfeeding. Some of the fallout may have already occurred elsewhere in the world: Australia’s last flu season hit children hard and early, and Nicaragua’s wave in early 2022 infected children at rates “higher than what we saw during the 2009 pandemic,” Aubree says. Gordon, an epidemiologist from the University of Michigan.

In the US, many hospitals are now admitting far more young and older children for respiratory illnesses than usual, says Mari Nakamura, a pediatric infectious disease specialist at Boston Children’s Hospital. The problem was exacerbated by the fact that many adults and school-age children avoided their usual contacts with influenza and RSV while those viruses were in exile, making it easier for the pathogen to spread once the crowds were reunited. “I wouldn’t be surprised,” Gordon told me, “if we see 50 to 60 percent of kids get the flu this year” — double the estimated typical rate of 20 to 30 percent. Caregivers get sick too; when I called Edwards, I could hear her husband and grandson coughing in the background.

By next year, more people’s bodies should be identified with the strains that circulate during the season, says Helen Chu, a physician and epidemiologist at the University of Washington. Experts also hope that tools to combat RSV will soon be greatly improved. There is currently no vaccine for the virus, and only one preventive drug is available in the US: a monoclonal antibody that is difficult to administer and available only to high-risk children. But at least one RSV vaccine and another, less cumbersome antibody therapy (already in use in Europe) are expected to get the FDA green light by next fall.

But even with the addition of better technology, fall and winter can be tough for many years to come. SARS-CoV-2 is here to stay and is likely to increase the respiratory burden by infecting people on its own or increasing the risk of co-infections that can worsen and prolong illness. Even non-overlapping illnesses can cause problems if they manifest in rapid succession: very severe bouts of COVID, for example, can damage the airways, making it easier for other microbes to colonize.

Several experts have begun to wonder whether even milder bouts with SARS-CoV-2 could make people more susceptible to other infections in the short or long term. Given the widespread effects of the coronavirus on the body, “we cannot be complacent” about that possibility, says Flor Muñoz Rivas, a pediatrician at Baylor College of Medicine. Mejias and Octavio Ramilo, also of Nationwide, recently found that among a small group of infants, those with recent SARS-CoV-2 infections appeared to have a more severe attack with a subsequent RSV attack. However, this trend needs more study; it’s not clear which children might be at greater risk, and Mejias doubts the effect would last more than a few months.

Gordon points out that some people might actually benefit from the opposite scenario: Recent contact with SARS-CoV-2 might bolster the body’s immune defenses against another respiratory invader for days or weeks. This phenomenon, called viral interference, wouldn’t stop an outbreak by itself, but it’s thought to be one reason why waves of respiratory illnesses don’t usually break out at the same time: the presence of one microbe can sometimes crowd out others. Some experts believe that last year’s record rise in Omicron helped carry the expected winter flu epidemic into the spring.

Even if all these variables were better understood, the vagaries of viral evolution could lead to reversals. A new variant of SARS-CoV-2 may yet appear; a new strain of flu could cause its own pandemic. RSV, on the other hand, is not thought to change shape that quickly, but the genetics of the virus are not well understood. Mejias and Ramil’s data suggest that the arrival of a bumpy strain of RSV in 2019 may have pushed local hospitalizations above their usual highs.

Behavioral and infrastructure factors could also confound the forecast. Healthcare workers have left their jobs en masse during the pandemic, and pediatric bed capacity in many hospitals has shrunk, leaving supply woefully inadequate for current demand. Vaccination rates against COVID among young children are also low, and many pediatricians are concerned that anti-vaccination sentiment could prevent other routine vaccinations from being administered, including those against the flu. Even temporary vaccination delays can have an effect: Muñoz Rivas points out that the early arrival of the flu this year, before many people have signed up for the shot, can now help spread the virus. New treatments and vaccines for RSV “could really, really help,” Nakamura told me, but “only if we use them.”

Next fall comes with a few guarantees: the seasonal schedule may not fix itself; viruses may not give us an evolutionary pass. Our immune system will probably be better prepared to fight off flu, RSV, rhinovirus, enterovirus, and others—but that alone may not be enough. However, what we can control is how we choose to arm ourselves. The past few years have shown that the world works know how to reduce rates of respiratory disease. “We’ve had so little infection during the time we’ve been trying to keep COVID at bay,” Edwards told me. “Is there anything to learn?”