Offering new revelations on the behavior of SARS-CoV-2, a National Institutes of Health (NIH) study suggests that young children and people with obesity may be significant vectors of viral transmission in households.

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NIH’s National Institute of Allergy and Infectious Diseases (NIAID) enlisted scientists from Henry Ford Health and other groups to participate in the project, which focused on incidence of SARS-CoV-2 infection in households with children and the role of allergic diseases in infection and transmission.

NIAID “wanted to get some answers about COVID in kids and in houses and families quickly,” study co-author Christine Johnson, PhD, MPH, chair of public health sciences at Henry Ford Health said in an interview with AMA.

Henry Ford Health is part of the AMA Health System Program, which provides enterprise solutions to equip leadership, physicians and care teams with resources to help drive the future of medicine.

Johnson also helms the Henry Ford Health Center for Allergy, Asthma & Immunology Research, which was charged with helping to collect data for the NIAID study.

She and her team contributed to the monitoring of 1,394 families from 2020 to 2021, sending testing kits to families and accepting blood and stool samples. Overall, 147 households comprising 261 participants tested positive for COVID-19, says the study, published in the Journal of Allergy and Clinical Immunology.

The goal was to assess sources of transmission: how it was spreading around households, and what role did children have in spreading it. How much of this was asymptomatic infection?

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Obesity emerged as a risk factor in acquiring the virus. Age was irrelevant in this association: anyone with obesity was more likely to get sick than people with normal weight, possibly because their immune system wasn’t optimized to fight off infection.

The findings “definitely showed that the more weight you have on you, the more likely you’re going to get infected … and transmit that infection to somebody else in the house,” Johnson said.

This wasn’t the case with asthma. People once assumed that pulmonary disease was a risk factor with COVID-19. The virus attaches itself to angiotensin-converting enzyme 2 (ACE2) receptors expressed in the lungs.

In other  studies, researchers found that people with allergic asthma have fewer ACE2 receptors. “Having asthma just didn't make a difference in transmission or in getting infected,” Johnson said.

Visit the AMA COVID-19 resource center for physicians to stay updated on the latest developments.

Although younger children had lower viral loads than teens and adults, they were most likely to transmit COVID-19 in their household.

“To me, it validates the concept that kids are great little vectors,” said Johnson. This may be because younger children tend to hug people more, whereas teens are likelier to keep to themselves, she speculated.

At least 75% of the children who acquired COVID-19 showed no symptoms. This suggests they unknowingly had virus in their noses but may have been spreading it to others. Schools ranked the highest as public sources of exposure compared with health clinics and grocery stores.

Looking back, closing schools was probably an effective way of cutting SARS-CoV-2 transmission prior to the widespread availability of safe and effective vaccines, Johnson said. That’s a key piece of information for policymakers to keep in mind when another pandemic comes along.

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Physicians are anticipating a difficult winter ahead, as COVID-19 resurges and mingles with influenza and respiratory syncytial virus (RSV).

RSV is heightened this year and appearing earlier, but it wasn’t around in 2021 when people were masking up, noted Johnson. Wearing a mask is one obvious way to avoid infection. This is especially important for people with compromised immune systems, who should be masking up at airports and on planes.

As the study findings imply, patients at high risk for worse outcomes from COVID-19 also should avoid close, unmasked contact with young children this winter, when possible, Johnson said.

Editor’s note: This article was originally published with a different headline.

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