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Immunity debt: why so many children are sick with RSV

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Recently, children’s hospitals across the country have been full of sick children, and it seems like every child has a cold these days. One of the viruses responsible, respiratory syncytial virus (RSV), is not new to pediatricians, but due to a recent rapid rise in cases, this may be the first time many are hearing about it. . RSV is a common childhood virus that typically circulates during the winter months and causes respiratory disease. This year, children’s hospitals saw an increase in cases earlier in the year, in late summer and early fall.

Although RSV can infect people of all ages, it usually does not cause severe symptoms in older children or adults with intact immune systems. RSV can cause symptoms in young children ranging from a mild cold to bronchiolitis, an infection of the small airways of the lung leading to inflammation and mucus buildup, which can lead to difficulty breathing in young children. Bronchiolitis is most common in children under 2 years old, and although most children with bronchiolitis recover at home within 7-10 days, some may need hospitalization for support with their breathing or IV fluids for hydration. Children younger than 6 months are at higher risk of serious illness. RSV bronchiolitis was a leading cause of pediatric hospitalizations during the winter months for many years prior to 2020.

Many respiratory viruses follow a predictable annual pattern as cases peak and decline in the community. For example, at Children’s Hospital Los Angeles where I work, RSV is most commonly seen in the winter months, along with influenza, the virus that causes influenza. In the United States, these viruses spread through communities in late fall, with case numbers peaking in the winter months and then finally dying out in the spring. Other viruses tend to peak in the summer months.

During the COVID-19 pandemic, prevention strategies – such as wearing a mask, physical distancing, and staying home from school and work – were aimed at curbing the spread of COVID-19, but they also reduced the spread of these common childhood viruses, including RSV , which spread easily from person to person, especially in group settings like daycares. This disrupted typical viral patterns, and the number of RSV positive cases and pediatric RSV hospitalizations in the winters of 2020 and 2021 decreased compared to previous years.. It’s unclear how long it will take for these viral patterns to return to their typical pre-pandemic cycles.

Now that most children are back in daycare and school at a time when masking is less prevalent, RSV has had the opportunity to spread among children whose immune systems have never met the virus before. This phenomenon has been called “immune debt” due to pandemic prevention measures. The first time the immune system encounters a virus, the symptoms of infection may be more severe as the body learns to fight off the virus, while subsequent infections tend to cause minimal or mild symptoms as the body now has of a model to effectively target the virus. Before the pandemic, most children were exposed to RSV before the age of 2 years. The current increase in pediatric cases of RSV suggests that children’s immune systems are “catching up” with typical childhood viruses and that young children, as well as older children who may not have been exposed in recent years , are at risk of infection. Additionally, mothers whose immunity to RSV has waned in recent years are less likely to pass protective antibodies to infants via breast milk.

RSV is spread from person to person through close contact with an infected person or through contact with infected secretions, such as infected droplets from a cough or sneeze. Although there is no RSV vaccine currently available, good hygiene measures such as washing your hands, keeping frequently used surfaces clean, and staying away from other people with cold symptoms can help prevent the spread of RSV.

Many children have had or will have multiple colds this season. Hospitals are already seeing children who have tested positive for multiple viruses (such as RSV, COVID-19 and influenza) at the same time or in rapid succession. The flu is set to have a similar increase in cases in the coming months. Parents can help protect themselves and their children against the flu by getting the flu shot this year, which is available for children 6 months and older, in addition to hand washing and other protective measures. hygiene.

Dr. Priya Edward is a pediatric infectious disease specialist at Children’s Hospital Los Angeles and a clinical assistant professor of pediatrics at USC’s Keck School of Medicine.