Covid is making flu and other common viruses act in unfamiliar ways
“That’s not typical for any time of year and certainly not typical in May and June,” said Thomas Murray, an infection-control expert and associate professor of pediatrics at Yale. Some children admitted to the hospital were co-infected with two viruses and a few with three, he said.
More than two years into the coronavirus pandemic, familiar viruses are acting in unfamiliar ways. Respiratory syncytial virus, known as RSV, typically limits its suffocating assaults to the winter months.
Rhinovirus, cause of the common cold, rarely sends people to the hospital.
And the flu, which seemed to be making a comeback in December after being a no-show the year before, disappeared again in January once the omicron variant of the coronavirus took hold. Now flu is back, but without one common lineage known as Yamagata, which hasn’t been spotted since early 2020. It could have gone extinct or may be lying in wait to attack our unsuspecting immune systems, researchers said.
The upheaval is being felt in hospitals and labs. Doctors are rethinking routines, including keeping preventive shots on hand into the spring and even summer. Researchers have a rare opportunity to figure out whether behavioral changes like stay-at-home orders, masking and social distancing are responsible for the viral shifts, and what evolutionary advantage SARS CoV-2 may be exercising over its microscopic rivals.
“It’s a massive natural experiment,” said Michael Mina, an epidemiologist and chief science officer at the digital health platform eMed. Mina said the shift in seasonality is explained largely by our lack of recent exposure to common viruses, making us vulnerable to their return.
In hospitals across the country, physicians are adjusting protocols that for decades reflected a predictable cycle of illnesses that would come and go when schools closed or the weather changed.
“You would see a child with a febrile illness, and think, ‘What time of the year is it?’ ” said Peter Hotez, a molecular virologist and dean for the National School of Tropical Medicine at Baylor College of Medicine in Houston.
For years, Theresa Barton, head of pediatric infectious diseases at University Health in San Antonio, has routinely championed the flu vaccine each fall and relaxed her advocacy by March and April, when the flu fizzled out. The new shift in seasonality, with flu cases rising last summer and then again this spring, made her rethink.
“You are like, ‘Oh man!’ in clinics. ‘Let’s get your flu shot,’ ” Barton said.
She and other infectious-disease specialists are also revisiting their response to RSV, a common virus that hospitalizes about 60,000 children younger than 5 each year, according to the Centers for Disease Control and Prevention. It can create deadly lung infections in preemies and other high-risk infants. The typical treatment for them is monthly shots of a monoclonal antibody, palivizumab, from around November through February. But last summer, RSV suddenly surged and this year it is causing trouble in May and June. Infectious-disease experts are carefully tracking cases so that they are prepared to reactivate the pricey protocol.
“We monitor number of cases so that if it exceeds a number, we are ready,” Murray said. The Yale hospital, which typically holds meetings to prepare for upswings in fall through spring, is preparing pandemic-fatigued staffers for out-of-season surges.
Even common colds seem a little more virulent and tenacious, according to Richard Martinello, a specialist in respiratory viruses at Yale School of Medicine.
“When people are getting colds, they do seem to be a little worse,” he said, emphasizing that so far the evidence is largely anecdotal.
The changes — and how and when they may revert to normal — reflect shifts in our own behavior during the pandemic as well as the interplay between SARS CoV-2 and other viruses, known as viral interference.
We evolved alongside pathogens, and our regular contacts with them usually allow our immune systems to reup the response without making us very sick.
The system has “enough memory to make it more like a good hearty booster than a bad infection,” Mina said.
The moment you stop seeing a virus on this regular cadence, as happened during the pandemic, that natural balance is upset, Mina said. The extraordinary measures we took to limit exposure to the coronavirus — necessary steps to contain a deadly new foe — also limited our exposure to…
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