As the case count of coronavirus infections continues to rise in China, the number of reported infections among children is remarkably low.
"We're seeing [about] 75,000 total cases at this point, but the literature is only reporting about 100 or so pediatric cases," says Terri Lynn Stillwell, a pediatric infectious disease expert at Mott Children's Hospital at the University of Michigan.
It's possible that many more kids are infected but don't get sick enough to seek medical treatment. It's also possible that some infected children may develop no symptoms at all.
"So far, it appears that more than 80% of the [coronavirus] infections are pretty mild, no more severe than the common cold,' says Cody Meissner, an infectious disease expert and professor of pediatrics at Tufts University School of Medicine. "And children appear to have even milder infections than adults," Meissner says. This is based on preliminary data, he says.
He points to the findings of a small study, published in JAMA. Researchers in Wuhan, China, identified nine hospitalized infants who had been diagnosed with COVID-19 after being infected by a family member. They ranged in age from one month to 11 months old. The researchers documented their symptoms. They found that four of the infants had fevers and two developed a cough. "It was very mild illness," Meissner says. None of the infants had severe complications.
So far, it seems the new virus is more likely to infect older adults, particularly people with chronic health problems. And those who have died from the virus in China tend to be much older, with an average age in their 70s.
Another group that public health officials worry about during an infectious disease outbreak is pregnant women. But so far there's no evidence that women suffer severe complications.
A small study published in The Lancet followed nine women who were tracked during their third trimester of pregnancy. They were all admitted to Zhongnan Hospital of Wuhan University in Wuhan, China, and were all confirmed to have the virus. They all delivered by C-section, and none of the women developed severe pneumonia or died. All gave birth to babies that appeared to be in relatively good health, with Apgar scores in the normal range in the minutes after birth.
To test whether the virus had been passed on, the researchers took samples of amniotic fluid, cord blood and breastmilk. "They did not find virus in those tissues or fluids," says Sallie Permar, a professor of pediatrics and immunology at Duke University School of Medicine. She was not involved in the study but reviewed the findings for NPR.
"The good news is we have not seen evidence of vertical transmission in coronaviruses," Permar says. But she says it's important to keep studying this novel virus because this initial research is based on so few cases.
In some ways, it's not completely surprising that there have not been a lot of reported cases of the new virus among young children. Going back to another coronavirus that caused harm with severe respiratory infection, "SARS was [also] mostly reported in adult populations and not children," Permar says. "So there may be similarities to this coronavirus."
It's not clear why young children may be less vulnerable. But there may be some protection from their mother.
"Infants are born with maternal antibodies," Permar says. "So whatever their mother had been exposed to, they may have some protection [against] when they're first born." She says whether this is contributing at all to the reports of a low degree of severity in infants "will be something to study going forward."
Meanwhile, children are certainly being affected by the current flu season in the United States.
DAVID GREENE, HOST:
All right. Another story we're following is the coronavirus outbreak. And it now appears that children may be less vulnerable to this novel virus. NPR's Allison Aubrey reports on two small studies out of China, both of which, experts say, offer some reassurance to parents.
ALLISON AUBREY, BYLINE: Given the thousands of cases of coronavirus in China, it may be surprising that the number of children known to be infected is remarkably low. Terri Stillwell is a pediatric infectious disease physician at the University of Michigan.
TERRI STILLWELL: Even though we are seeing almost 75,000 total cases at this point, the literature is really only reporting about a hundred or so pediatric cases.
AUBREY: It's likely that more kids have been infected with the virus but don't get sick enough to need medical attention. Or, in some cases, kids may have no symptoms at all. Cody Meissner is an infectious disease expert and professor of pediatrics at Tufts University School of Medicine.
CODY MEISSNER: More than 80% of the infections are pretty mild, no more severe than the common cold. And children have even milder infections.
AUBREY: Meissner says the data is preliminary, but he points to the findings of one new study out of China. Physicians evaluated nine infants who'd been hospitalized after getting the coronavirus from a family member.
MEISSNER: It turned out that it was a very mild illness. Some had a cough. Fever was - it was very low-grade. It was really a mild upper respiratory tract infection or even no symptoms.
AUBREY: So far, it seems the new virus is more likely to infect older adults, particularly people with chronic health problems. And those who've died from the virus in China tend to be much older, averaging in their 70s.
Now, another group that public health officials worry about during an infectious disease outbreak is pregnant women. And Sallie Permar, a professor of pediatrics and immunology at Duke University School of Medicine, says there's already some evidence coming out of China that's reassuring.
SALLIE PERMAR: There has been a small study that was recently released in The Lancet that followed women who were infected in their third trimester of pregnancy.
AUBREY: Now, when these women delivered, none of them had severe complications, such as severe pneumonia, and neither did their babies. To assess whether the virus had been passed on, researchers tested samples of amniotic fluid and breast milk.
PERMAR: And so far, from this small study, they did not find virus in those tissues or fluids. And the good news is that we haven't seen evidence of vertical transmission in coronaviruses.
AUBREY: More studies are needed, Permar says, but these are important findings from the epicenter of the outbreak. As for the risk that coronavirus poses to people outside of China, University of Michigan's Terri Stillwell says it's important for public health officials to be vigilant. The situation is fluid. But she says if you live in the U.S., there's likely a much bigger threat this season.
STILLWELL: I would be remiss as a pediatric infectious disease physician to not mention that our flu season is still in full swing, with over 26 million cases of influenza and about 14,000 deaths here in the U.S. alone. And so certainly, the influenza season is probably a much riskier thing at this point.
AUBREY: Every year, more than a hundred children in the U.S. die from the flu. And the majority of those deaths, according to the CDC, occur in kids who were not vaccinated.
Allison Aubrey, NPR News.
(SOUNDBITE OF LO DINO'S "WOULD YOU") Transcript provided by NPR, Copyright NPR.