Children are susceptible to the new coronavirus that causes COVID-19, the potentially deadly respiratory illness now spreading rapidly worldwide. Although they typically have few or no symptoms, kids may transmit the virus to others, including more vulnerable older family members.

The New England Journal of Medicine this week published a letter to the editor describing cases of COVID-19 among children in Wuhan, China, where the global pandemic first emerged. The journal has made this and other coronavirus content freely available online.

Between January 7 and January 15, a total of 366 hospitalized children and adolescents, age 16 or younger, were included in a retrospective study of respiratory infections at three branches of Tongji Hospital, located within about 20 miles of one another in central Wuhan.

Among the 366 children, the most commonly detected pathogens were influenza A virus (6.3%) and influenza B virus (5.5%). SARS-CoV-2, as the novel coronavirus is officially known, was detected in six children (1.6%). The children ranged in age from one to seven years.

Four of these children were girls, and two were boys. This is different from the sex ratio of adult patients. In China, men develop serious COVID-19 illness more often than women, possibly related to their higher rate of smoking. But the number of cases in children is too small to draw any conclusions about differences in susceptibility based on sex.

All the children had previously been healthy—another difference from adults, as people with preexisting illnesses, such as heart disease, lung disease or diabetes, are more prone to severe complications.

All the children had a fever—often higher than 102 degrees—which lasted from three to 11 days. All six had a cough, and four experienced vomiting. Lab tests showed that a majority had low levels of immune system white blood cells. This is unusual because infections typically lead to higher levels of immune cells as the body tries to fight off invaders. CT scans showed that four of the children had evidence of pneumonia, while the other two had normal scans.

The children were hospitalized for five to 13 days. One was admitted to a pediatric intensive care unit. They received various types of treatment, including the antiviral drug ribavirin, the flu medication Tamiflu (oseltamivir), steroids to control inflammation and supplemental oxygen. The child in intensive care received an infusion of antibodies from healthy blood donors. All of them survived.

Because most children who contract COVID-19 have no symptoms or only mild symptoms, a much larger number were probably infected than this small subset thatbecame sick enough to require hospital care. This differs from the seasonal flu, which is more likely to cause severe illness in both young children and elderly people.

The authors did not report whether the children transmitted the virus to others. However, based on what we know about other respiratory viruses, it is likely that kids can carry the new coronavirus—even if it doesn’t make them sick—and pass it on to others.

For this reason, “social distancing” measures, such as staying home and avoiding crowds, should include children. These measures can help protect more vulnerable people, including older individuals, those with coexisting health conditions and those with compromised immune systems, such as people living with HIV and cancer patients undergoing chemotherapy.

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