The Conversation: COVID-19, RSV and flu are straining health care systems – two epidemiologists explain what the ‘triple threat’ means for children

Every fall and winter, viral respiratory illnesses such as the common cold and seasonal flu keep children from school and social activities. But this year more children than usual are arriving at emergency departments and hospitals.

In California, the Orange County Health Department declared a state of emergency through early November 2022 due to a record number of pediatric hospitalizations for respiratory infections. In Maryland, emergency rooms have run out of beds because of an unusually high number of severe respiratory syncytial virus, or RSV, infections. So emergency departments are forced to refer patients across state lines for care.

In the US, the cold respiratory virus season started earlier than usual this year. Since peak infections usually occur in late December or January, this uncharacteristic initial wave suggests that the situation could be much worse for people of all ages, especially children.

We are epidemiologists specializing in epidemiological analysis for emerging disease threats, including respiratory infections. We look closely for patterns in these transitions, and we pay special attention when the patterns are unusual. We have become increasingly concerned about the number and emerging patterns of pediatric hospitalizations over the past few months.

‘Triple Threat’

In early November, the Centers for Disease Control and Prevention issued a health advisory about increased activity in respiratory infections — particularly among children. The CDC and other health experts are warning of a so-called “triple threat” of respiratory illness from RSV, influenza — or seasonal flu — and COVID-19.

The underlying reasons for the convergence of these viruses and the increase in infections so early in the season are not yet clear. But health experts have some clues about the contributing factors and what it could mean for the coming months.

When it comes to COVID-19, another winter wave of infections is expected in 2022, similar to the pattern seen in 2020 and 2021. Last winter’s increase stemmed from a combination of factors, including the emergence and spread of new viral variants, more people gathering indoors rather than distancing outside, and people coming together for the 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. 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 proven somewhat unpredictable during the COVID-19 pandemic, it almost always arrives in late October. Flu season also arrived about a month earlier and in higher numbers than in recent history. From our reading of the data, pediatric flu hospitalizations for this time of year are becoming 10 times higher than they have been for more than a decade.

RSV infections follow a similar seasonal pattern to the flu, peaking in the winter months. But this year, there was an unexpected heat wave, preceding the start of the normal fall respiratory virus season.

In typical years, RSV receives little media attention. It is incredibly common and usually only causes mild illness. In fact, most children contract the virus before the age of 2.

But RSV can be a formidable respiratory infection with serious consequences for children under age 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 especially at risk

Children, especially young children, tend to get sick with the flu and RSV more often than other age groups. But infants younger than 6 months seem to suffer the most, with nearly twice the risk of RSV-related death than other children younger than 5. The COVID-19 hospitalization rate is also four to five times higher for infants than for older children.

One reason the youngest children are at greater risk is that their immune systems are not yet fully developed and do not produce the strong immune response seen in most adults. What’s more, infants under 6 months of age – who are at highest risk of severe illness – are still too young to be vaccinated against influenza or COVID-19.

These viruses present challenges on their own, but their co-transmission and coincident increase in infections create a perfect storm for multiple viruses to infect the same person at once. Viruses can act together to evade immunity and cause damage to the respiratory tract.

Such co-infections are usually uncommon. However, the likelihood of co-infection is significantly higher in children than in adults. Co-infections can be difficult to diagnose and treat, and can ultimately lead to more severe disease, complications, hospitalization, and death.

factors behind triple threat

There are a few reasons why the United States may be seeing an increase in respiratory infections among children. First, COVID-19 protection strategies actually help prevent transmission of other respiratory pathogens. School and daycare closures also likely put children at least at risk for various respiratory viruses in common.

These and other efforts to stop the spread of COVID-19 seem to have suppressed the widespread spread of other viruses, including influenza and RSV. As a result, the US saw an overall decline in non-COVID respiratory infections – and almost no flu season in the winter of 2020.

Decreased viral activity means babies have missed out on some of the exposure to viruses and other pathogens that usually help build immunity, especially during the first few years of life. As we continue into this season, the resulting so-called “immune debt” may be contributing to an excess of child respiratory infections.

To further complicate the picture, the changing nature of viruses, including the emergence of new COVID-19 variants and the natural evolution of seasonal influenza viruses, means we may see particularly infectious strains or a unique combination of strains that are more cause serious illness.

people can take proactive steps

The initial surge in respiratory infections with higher rates of hospitalization highlights the importance of prevention. The best tool we have for prevention is vaccination. Vaccines to protect against COVID-19 and influenza are available and recommended for everyone over the age of 6 months. They have been shown to be safe and effective, and they can save and even save lives.

Notably, the most recent data on the newly updated bivalent COVID-19 booster vaccine suggests that it produces a more robust antibody response against the current circulating Omicron variant than the original COVID-19 vaccines.

Vaccination during pregnancy is the best way to protect babies under 6 months of age from flu and COVID-19. 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%. Vaccinating other caregivers, family, and friends can also help protect babies.

Other preventive measures, such as washing hands, covering sneezes and coughs, staying home and isolating when sick, can help protect a community from these viruses and others. Paying attention to local public health advisories can help people get the most up-to-date information and make informed decisions to keep themselves and others – of all ages – safe.

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