Younger children may be vulnerable to the reemergence of common respiratory viruses such as influenza and respiratory syncytial virus (RSV) as COVID-19 restrictions wane, experts say. The impact could be detrimental.
The COVID-19 pandemic and the implementation of preventative measures such as social distancing, travel restrictions, mask use, and shelter in place, reduced the transmission of respiratory viruses, according to the Centers for Disease Control and Prevention. However, because older infants and toddlers have not been exposed to these bugs during the pandemic, they are vulnerable to suffering severe viral infections.
“[We’ve] been in the honeymoon for 18 months,” said Christopher J. Harrison, MD, professor of pediatrics and pediatric infectious diseases at Children’s Mercy Hospitals and Clinics in Kansas City, Mo. “We are going to be coming out of the honeymoon and the children who didn’t get sick are going to start packing 2 years’ worth of infections into the next 9 months so there’s going to be twice as many as would be normal.”
The CDC issued a health advisory in June for parts of the southern United States, such as Texas, the Carolinas, and Oklahoma, encouraging broader testing for RSV – a virus that usually causes mild, cold-like symptoms and is the most common cause of bronchiolitis and pneumonia in children – among those who test negative for COVID-19. Virtually all children get an RSV infection by the time they are 2 years old, according to the CDC.
In previous years, RSV usually spread during the fall and spring seasons and usually peaked late December to mid-February. However, there’s been an offseason spike in the common illness this year, with nearly 2,000 confirmed cases each week of July.
Richard J. Webby, PhD, of the infectious diseases department at St. Jude Children’s Research Hospital, Memphis, Tenn., said that although RSV transmits more easily during the winter, the virus is able to thrive during this summer because many children have limited immunity and are more vulnerable to catching the virus than before. Population immunity normally limits a virus to circulating under its most favorable conditions, which is usually the winter. However, because there are a few more “susceptible hosts,” it gives the virus the ability to spread during a time when it typically wouldn’t be able to.
“Now we have a wider range of susceptible kids because they haven’t had that exposure over the past 18 months,” said Dr. Webby, who is on the World Health Organization’s Influenza Vaccine Composition Advisory Team. “It gives the virus more chances to transmit during conditions that are less favorable.”
Dr. Harrison said that, if children continue to take preventative measures such as wearing masks and sanitizing, they can delay catching the RSV – which can be severe in infants and young children – until they’re older and symptoms won’t be as severe.
“The swelling that these viruses cause in the trachea and the bronchial tubes is much bigger in proportion to the overall size of the tubes, so it takes less swelling to clog up the trachea or bronchial tube for the 9-month-old than it does of a 9-year-old,” Dr. Harrison said. “So if a 9-year-old was to get RSV, they’re not going to have nearly the same amount symptoms as the 9-month-old.
Dr. Harrison said delaying RSV in children was never an option before because it’s a virus that’s almost impossible to avoid.
“Hopefully, the mask means that if you get exposed, instead of getting a million virus particles from your classmate or your playmate, you may only get a couple thousand,” Dr. Harrison explained. “And maybe that’s enough that you can fight it off or it may be small enough that you get a mild infection instead of a severe infection.”
A summer surge of RSV has also occurred in Australia. A study published in Clinical Infectious Diseases found that Western Australia saw a 98% reduction in RSV cases. This suggests that COVID-19 restrictions also delayed the RSV season.
Dr. Webby said the lax in penetrative measures against COVID-19 may also affect this upcoming flu season. Usually, around 10%-30% of the population gets infected with the flu each year, but that hasn’t happened the past couple of seasons, he said.
“There might be slightly less overall immunity to these viruses,” Dr. Webby said. “When these viruses do come back, there’s a little bit more room for them to take off.”
Although a severe influenza season rebound this winter is a possibility, Australia continues to experience a historically low flu season. Dr. Harrison, who said the northern hemisphere looks at what’s happening in Australia and the rest of the “southern half of the world because their influenza season is during our summer,” hopes this is an indication that the northern hemisphere will also experience a mild season.
However, there’s no indication of how this upcoming flu season will hit the United States and there isn’t any guidance on what could happen because these historically low levels of respiratory viruses have never happened before, Dr. Webby explained.
He said that, if COVID-19’s delta variant continues to circulate during the fall and winter seasons, it will keep other viruses at low levels. This is because there is rarely a peak of activity of different viruses at the same time.
“When you get infected with the virus, your body’s immune response has this nonspecific reaction that protects you from anything else for a short period of time,” Dr. Webby explained. “When you get a lot of one virus circulating, it’s really hard for these other viruses to get into that population and sort of set off an epidemic of their own.”
To prepare for an unsure influenza season, Dr. Harrison suggests making the influenza vaccine available in August as opposed to October.
Dr. Harrison and Dr. Webby reported no conflicts of interest.
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