According to the World Health Organization, there have been nearly 8 million confirmed cases of COVID-19—the disease caused by the SARS-CoV-2 virus—as of June 16. In April, the US Centers for Disease Control and Prevention (CDC) reported that about 2 percent of US cases were in children younger than 18 years, and evidence from China, Europe, and the US has indicated that children tend to have milder cases. In a study published today in PLOS Medicine, researchers in China report that even among children hospitalized with confirmed SARS-CoV-2 infections, their illnesses were mild compared to adults’ experiences.

This study “adds to the growing body of literature that is giving us some experience with what COVID-19 looks like in children, which, as we’re learning, is very different than what COVID-19 looks like in adults,” says Jennifer Schuster, a pediatric infectious disease physician at...

In the new study, a research team documented the cases of 34 children, ages one month to 12 years, admitted between January 27 and February 23, 2020, to one of four hospitals in Hubei—the central Chinese province where Wuhan is—or Shaanxi, which is a province in northwest China. The patients, 14 boys and 20 girls, all had a confirmed SARS-CoV-2 infection.

The most common symptoms were fever (76 percent) and cough (62 percent), and vomiting and diarrhea were each present in 12 percent of subjects. These symptoms were more frequent in adults admitted to the hospital for COVID-19, the CDC reported in April: 86 percent of adult patients had a cough, 85 percent had fever or chills, nearly 27 percent had diarrhea, and about 25 percent had nausea or vomiting. Only six pediatric patients in the new study had underlying health conditions, such as asthma or a heart defect, while the CDC found that about 90 percent of adults had underlying conditions. Nearly half of the children were also infected with another respiratory pathogen, such as influenza A or B or Mycoplasma pneumoniae, which typically causes sore throat and cough in kids.

What we’re seeing more and more from the data that comes out is that child-to-child or child-to-adult spread is actually not common.

—Jennifer Schuster, Children's Mercy Hospital

Eva Grayck, a pediatric critical care physician and researcher at Children’s Hospital Colorado who was not involved in the study, says she was struck by the number of coinfections that the authors observed, which is different than what she has seen in Colorado. This high rate of coinfections could be explained by the seasons—China was in the middle of winter during this study—or perhaps it was early enough in the course of the pandemic that they hadn’t yet implemented steps to reduce the spread, she adds.

Only one child exhibited ground-glass opacities, a type of lesion that looks like a hazy area on a lung computed tomography (CT) scan and is commonly observed in hospitalized adults with COVID-19. In contrast, 32 patients either had at admission or later developed lesions that appeared as patchy, dense shadows in their lung lobules as visualized by CT scan. Although the children recovered from cough and fever within a few days and all were discharged from the hospital within 15 days, 24 still had these lesions in their lungs when they were discharged.

See “AI Learns from Lung CT Scans to Diagnose COVID-19

“We don’t get CT scans on anyone, unless it’s clinically indicated,” says Marion Sills, a pediatric emergency physician and researcher at Children’s Hospital Colorado who did not participate in the work. The subjects in the study got three CT scans, which makes it harder to generalize those results to the patients Sills has seen.

Plus, the study’s age ranges “eliminated the sickest group that we’ve identified” in the US, Sills says. “The later teens, who fall within our pediatric population, have been some of our sickest patients,” she explains, adding that the authors may have missed sicker babies younger than one month as well. The authors did not respond to requests for an interview. 

In terms of transmission, 13 had a family member with COVID-19. While 18 total had been exposed to a suspected case, 16 patients had no clear source of transmission. “Family cluster transmission was found to be common in our pediatric patients. There have been few reports of the infection dynamics from pediatric patients to their caregivers, although transmission from adults to children has been identified with confirmed evidence,” the authors write. “However, no evidence was shown regarding the transmission route from pediatric patients to their caregivers and close-contact family members.”

Understanding transmission better could help inform public health policy as schools and childcare centers decide how and whether to reopen or not, says Schuster. “Initially, there was a lot of thought that this virus could be spread by children in congregate settings, which is common for other respiratory viruses like influenza. What we’re seeing more and more from the data that comes out is that child-to-child or child-to-adult spread is actually not common,” she says.

Other studies propose biological explanations for the lower levels of disease seen in children. And a modeling study published today in Nature Medicine estimates that people younger than 20 years of age are about half as susceptible to coronavirus infection as people older than 20.

The study is “a nice early summary of observations around pediatrics and highlights some of the differences in the pediatric population in terms of presentation compared to adults, which is going to be very important for recognizing and appropriately treating pediatric patients,” says Grayck. The authors don’t mention COVID-19–related multi-system inflammatory syndrome in children that’s been identified recently, she adds. “I’ve heard of it more in Europe and the US,” she says, and it will be interesting to look into whether it’s affecting kids in Asia as well.

C. Zhang et al., “Clinical and epidemiological characteristics of pediatric SARS-CoV-2 infections in China: A multicenter case series,” PLOS Medicine, doi:10.1371/journal.pmed.1003130, 2020.

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