The following essay is reprinted with permission from The Conversation, an online publication covering the latest research.
Every fall and winter, viral respiratory diseases like the common cold or seasonal flu keep children out of school and from participating in social activities. This year, however, more children are ending up in hospitals .
In California, the Orange County health department declared a state of emergency in early November 2022 due to record numbers of pediatric hospitalizations for respiratory infections. In Maryland, emergency rooms have run out of beds because of the unusually high number of severe respiratory syncytial virus, or RSV, infections. There are emergency departments that have to refer patients from other states for care.
The U.S. winter respiratory virus season began earlier than usual this year. Peak infections typically occur in December or January. This early outbreak suggests that the situation could worsen for all ages, especially children.
We are epidemiologists with expertise in epidemic analysis for emerging disease threats, including respiratory infections. We pay close attention to the unusual patterns in these infections and monitor them closely. We have become increasingly concerned about the number of pediatric hospitalizations in the last few months, and the emerging pattern.
The ‘triple threat’
In early November, the Centers for Disease Control and Prevention issued a health advisory about increased activity in respiratory infections – especially among children. The CDC and other health experts are warning of the so-called “triple threat” of respiratory illness from RSV, influenza – or the seasonal flu – and COVID-19.
The underlying causes of the confluence of these viruses and the rise in infections so early in the year are still not clear. However, experts in health have some clues as to the contributing factors and what it could all mean for the months ahead.
When it comes to COVID-19, 2022 is expected to usher in another winter wave of infections, similar to patterns seen in 2020 and 2021. The previous winter surges were caused by a variety of factors including the spread of new viruses, more people gathering indoors than outside, and people getting together for holidays.
But unlike previous pandemic winters, most COVID-19 precautions – such as using masks in public areas or avoiding group activities – are more relaxed than ever. Together with the looming threat of new variants, it is difficult to predict how big the next COVID-19 wave could be.
And while the seasonal flu has proved somewhat unpredictable during the COVID-19 pandemic, it nearly always hits during late October. Flu season arrived about a month earlier than usual and in higher numbers than ever before in recent history. By our read of the data, pediatric flu hospitalizations are nearing 10 times what has been seen for this time of year for more than a decade.
RSV infection tends to follow the same seasonal pattern as flu. They peak in winter months. But this year, there was an unexpected summer wave, well before the start of the typical fall respiratory virus season.
In most years, RSV receives very little media attention. It is extremely common and causes little to no illness. In fact, most children encounter the virus before age 2.
But RSV can be a formidable respiratory infection with serious consequences for children under 5, especially infants. It is the most common cause of lower respiratory infections in young children, and more severe illnesses can lead to pneumonia and other complications, often requiring hospitalization.
Why children are particularly at risk
Children, especially young children, tend to get sicker from flu and RSV than other age groups. But infants younger than 6 months old stand to suffer the most, with nearly double the risk of RSV-related death compared to other children younger than 5. COVID-19 hospitalization rates are also four to five times higher for infants than older children.
The reason that children younger than 6 months are more at risk is because their immune systems don’t have the same strength as adults and they aren’t producing the robust immune response. What’s more, infants younger than 6 months – who are most at risk of severe disease – are still too young to be vaccinated against influenza or COVID-19.
Although these viruses pose challenges on their own, their co-circulation and concomitant surges in infection create an ideal storm for multiple viruses infecting the same person at the same time. Viruses might even act together to evade immunity and cause damage to the respiratory tract.
Such co-infections are typically uncommon. However, the likelihood of co-infection is substantially higher for children than adults. Co-infections can be difficult to diagnose and treat, and can ultimately lead to greater disease severity, complications, hospitalization and death.
Factors behind the triple threat
There are several reasons why the U.S. might be experiencing a rise in pediatric respiratory infections. First, COVID-19 protection strategies actually help prevent the transmission of other respiratory pathogens. Children are less likely to be exposed to different respiratory viruses if daycare or school is closed.
These and other efforts to prevent the spread of COVID-19 seem to have suppressed the broad circulation of other viruses, including influenza and RSV. As a result, the U.S. saw an overall drop in non-COVID respiratory infections – and an almost nonexistent flu season in the winter of 2020.
Children are less likely to be exposed to viruses and other pathogens, which can help build immunity, especially in the first few years. The resulting so-called “immunity debt” may contribute to an excess of pediatric respiratory infections as we continue into this season.
To further complicate the picture, the changing nature of viruses, including theemergence of new COVID-19 variants and the natural evolution of seasonal influenza viruses, means that we could be seeing a unique combination of particularly transmissible strains or strains that cause more severe illness.
Proactive steps people can take
The importance of prevention is highlighted by the rapid rise in respiratory infections and high rates of hospitalization. Vaccination is the best way to prevent these infections. Vaccines that protect against COVID-19 and influenza are available and recommended for everyone over 6 months of age. They are safe and effective and can save lives.
In particular, most recent data on the newly updated bivalent COVID-19 booster vaccine suggests that it produces a more rigorous antibody response against the current circulating omicron variants than the original COVID-19 vaccines.
The best way to protect infants younger than 6 months old against flu and COVID-19 is by vaccination during pregnancy. When a pregnant mother is vaccinated, maternal antibodies cross the placenta to the baby, reducing the risk of COVID-19 hospitalization in young infants by 61%. Infants can also be protected by vaccination of their caregivers, friends, and family.
Other preventive measures such as hand-washing and covering coughs and sneezes, staying home, and isolating yourself when you are sick can help protect the community. People can also learn the latest information from local public health advisors and make informed decisions to keep their family and friends safe.