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At one point last month, children were admitted to Yale New Haven Children’s Hospital with a surprising array of seven respiratory viruses. They had adenoviruses and rhinoviruses, human respiratory syncytial virus and metapneumovirus, influenza and parainfluenza, as well as the coronavirus, which many specialists say is to blame for the unusual increases.
“That’s not typical for any time of year and it’s 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 unknown ways. Respiratory syncytial virus, known as RSV, usually limits its suffocating attacks to the winter months.
The rhinovirus, which causes the common cold, rarely sends people to the hospital.
And the flu, which seemed to be making a comeback in December after not showing up the year before, disappeared again in January once the omicron variant of the coronavirus took hold. Now the flu is back but without a common lineage known as the Yamagata, which hasn’t been seen since the early 2020s. It could be extinct or lurking to attack our unsuspecting immune systems, the researchers said.
The turmoil is being felt in hospitals and laboratories. Doctors are reconsidering routines, including the availability of preventive shots during the spring and even the summer. Researchers have a rare opportunity to find out if behavioral changes such as stay-at-home orders, mask wearing and social distancing are responsible for the viral changes, and what evolutionary advantage SARS CoV-2 may be exerting. over their microscopic rivals.
The “stealth” omicron variant BA.2 is expected to soon become the dominant strain. Here’s what you need to know about a possible new wave of infections. (Video: Brian Monroe, John Farrell/Mademoiselleosaki)
“It’s a massive natural experiment,” said Michael Mina, an epidemiologist and chief scientific officer at the digital health platform eMed. Mina said the change in seasonality is largely explained by our lack of recent exposure to common viruses, making us vulnerable to their return.
In hospitals across the country, doctors are adjusting protocols that for decades reflected a predictable cycle of illnesses that came and went when schools closed or the weather changed.
“You would see a child with a febrile illness and think, ‘What time of year is it?’ said Peter Hotez, a molecular virologist and dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston.
For years, Theresa Barton, chief of pediatric infectious diseases at University Health in San Antonio, has routinely advocated the flu shot each fall and relaxed her defense in March and April, when the flu died down. The new shift in seasonality, with flu cases surging last summer and then again this spring, made her rethink.
“You’re like, ‘Oh man!’ in clinics. ‘We’re going to get you vaccinated against the flu,’” Barton said.
She and other infectious disease specialists are also reviewing their response to RSV, a common virus that hospitalizes about 60,000 children under the age of 5 each year, according to the Centers for Disease Control and Prevention. It can create deadly lung infections in premature babies and other high-risk babies. The typical treatment for them is monthly injections of a monoclonal antibody, palivizumab, from around November through February. But last summer RSV surged and this year it’s causing problems in May and June. Infectious disease experts are carefully tracking cases to be prepared to reactivate the costly protocol.
“We monitor the number of cases so that if it exceeds a number, we are ready,” Murray said. Yale Hospital, which normally holds meetings to prepare for upticks from fall through spring, is preparing pandemic-fatigued staff for out-of-season upticks.
Even common colds seem a bit more virulent and tenacious, according to Richard Martinello, a respiratory virus specialist at Yale School of Medicine.
“When people get a cold, they seem to be a little worse,” he said, stressing that the evidence so far is largely anecdotal.
The changes, and how and when they may return to normal, reflect changes in our own behavior during the pandemic, as well as the interaction between SARS CoV-2 and other viruses, known as viral interference.
We co-evolved with pathogens, and our regular contacts with them usually allow our immune systems to kick-start the response without making us seriously ill.
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 at 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 (steps necessary to contain a deadly new enemy) also limited our exposure to other viruses. If you’re re-exposed to a virus after too long, you may not be able to protect yourself as well, leading to unseasonable population surges and surprisingly virulent infections for people.
That, Mina and others say, is what happened once people took off their masks and began gathering indoors. The viruses began to circulate out of season because the population’s immunity was low, even if other conditions for them were not optimal.
“All of these decisions have consequences,” Murray said. “You do the best you can with the information you have.”
The same immunological memory process is already well documented for other phenomena, Mina said, such as shingles in people in their 35s and 40s, a reactivation of the chickenpox virus that typically affects older adults or people with weakened immune systems.
Before the advent of chickenpox vaccines, people were typically infected as children and then had a series of natural booster events throughout their lives, resetting their immunity when they came into contact with infected friends and then their relatives. own children and their children’s friends.
Now that those children are protected, they don’t give their parents those natural urges, making those adults vulnerable to the virus in the form of shingles.
That phenomenon will be short-lived, as younger people who are protected by the chickenpox vaccine get older and will not be at risk of getting shingles.
While vaccines disrupt the viral landscape by restricting the spread of infections, an entirely new virus, SARS Cov-2, is doing so during the pandemic by interacting with its more common rivals.
It’s still unclear whether the drop in flu cases in January, for example, was caused entirely by people moving away from each other as omicron spread, or whether the coronavirus acted to push aside its more common rival. through some other mechanism.
“It’s a wonderful question, if omicron kicked him out,” said Xiaoyan Song, director of infection control at the National Children’s District Hospital. Even more mysterious is the role covid played in knocking Yamagata out of the game. When the flu returned this spring, that lineage was nowhere to be found.
Ellen Foxman, an immunobiologist at Yale School of Medicine, has spent years exploring how viruses interact and what genetic and environmental factors mean the same virus can cause a cold in one person and make another seriously ill.
It’s a high-tech company that uses cells from the nose and lungs to grow human airway tissue in the lab before infecting it with viruses, along with environmental pollutants like cigarette smoke.
The study of the lining of the nasal passages has provided information on what is known as innate immunity. Once those cells detect a virus, they activate antiviral defenses and block other viruses. That process may help explain why the long-awaited double pandemic of the coronavirus and other viruses, likely inhibited by remote work and mask-wearing in the winter of 2020-2021, still didn’t happen last winter, despite co-infections. sporadic
The cohort of babies born in the last two years will yield a lot of information. Normally, a child under 5 years of age has a virus in the nose on average 26 of the 50 weeks of the year. RSV and serious rhinoviruses infections in those early years are associated with the development of asthma later in life.
“These children were infection-free at a crucial time in lung development,” Foxman said, making them key to understanding the relationship between viral infection and asthma.
Still, it’s unclear what the future holds as covid settles among us.
“It will take time and even years to see what the new equilibrium will look like,” Martinello said.
Mina anticipates that the coronavirus, like other respiratory viruses, will fall into a seasonal circulation pattern once the population’s immunity increases, decreasing what is known as the “force of infection.”
“When you have a lot of people who don’t have immunity, the impact of the season is less. It’s like free rein,” Mina said. The virus “can overcome seasonal barriers.”
All of those changes will be affected by other environmental factors, says Barton, as climate change alters seasonal weather patterns.
Despite those ongoing uncertainties, for many researchers the upheaval caused by the pandemic has reinforced known strategies to prevent infection.
Scott Hensley, a microbiologist at the University of Pennsylvania Perelman School of Medicine, isn’t convinced the Yamagata flu is gone forever. It may still be circulating, undetected, at very low levels, he said, ready to reappear on the scene. Still, there is a tried and true method to protect ourselves: through vaccination.
“Even in years where the vaccines don’t match, there is some level of protection,” Hensley said, “that prevents hospitalizations and deaths.”
For Foxman, the lab scientist, the silver lining of the pandemic has been the way it will advance science.
Even as she continues to invest in high-tech experiments in her lab, Foxman says the biggest lesson the pandemic has taught her about stopping the spread of viral infections comes from simple changes in behavior, like wearing masks, that she believes they should continue strategically. circumstances.
“We need to carry forward some of the lessons we’ve learned,” Foxman said.
Source: www.washingtonpost.com