A coronavirus outbreak that originated in Wuhan, China, has killed at least 494 people and infected more than 24,000 other people since December.

So far, the coronavirus has infected very few children.

A children's hospital in Wuhan said this week that a 30-hour-old infant whose mother has the coronavirus tested positive for the virus too.

While it's possible that the coronavirus jumped from the mother to the child in the womb, one expert said it was more likely the infant caught the illness after birth.

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A 30-hour-old infant born in a children's hospital in Wuhan, China, has become the youngest person to catch the new coronavirus.

The newborn's mother has the coronavirus, the South China Morning Post reported on Wednesday, citing the state broadcaster CCTV. The baby's case raised the possibility that the new virus could jump from person to person via vertical transmission, or when a person passes a virus to their child in the womb, during childbirth, or via breast milk.

"We should be concerned about the possible new transmission route of the coronavirus," Zeng Lingkong, a senior physician at the Wuhan children's hospital's neonatal department, told the Post, adding that pregnant people should stay away from people with the coronavirus.

CCTV said the infant's vital signs were stable, according to the Post. A picture published by China's People's Daily newspaper showed the infant in an incubator.

However, Stephen Morse, an epidemiologist at the Mailman School of Public Health at Columbia University, told Business Insider that an in-utero transmission was improbable.

"It's more likely that the baby contracted the virus from the hospital environment, the same way healthcare workers get infected by the patients they treat," Morse said. "It's quite possible that the baby picked it up very conventionally — by inhaling virus droplets that came from the mother coughing."

There is no evidence that the two other coronaviruses that have caused major outbreaks — severe acute respiratory syndrome, or SARS, and Middle East respiratory syndrome, or MERS — are capable of vertical transmission.

The infant probably contracted the virus after birth

Other viruses, like HIV and Zika, can pass through the placenta and infect an unborn fetus. During labor and delivery, a newborn can also contract HIV through exposure to infected blood and bodily fluids.

"A lot of the transmission that we saw in HIV was actually not in utero but exposure of the baby while being born," Morse said.

The infant that got the new coronavirus could have been infected during birth in a similar way, he added. But unlike HIV, this coronavirus is a respiratory infection and doesn't jump from person to person via blood, but via phlegm and saliva droplets.

A baby wearing a protective face mask in a stroller at a Hong Kong rail station. Anthony Wallace/AFP/Getty

"For a respiratory virus, it would be pretty unusual," Nancy Messonnier, the director of the Centers for Disease Control and Prevention's Center for the National Center for Immunization and Respiratory Diseases, said on Wednesday of the possibility of in-utero transmission. "This is really the first such report that we've seen."

Xinhua, China's state-run press agency, said a woman with the coronavirus gave birth to a healthy child in Heilongjiang province on Monday, Newsweek reported.

Few children have contracted the coronavirus so far

From December 31, when the outbreak was first reported, to January 22, no cases were recorded in children under 15.

In total, the coronavirus has killed at least 494 people and infected more than 24,000 other people. (For the latest case total, death toll, and travel information, see Business Insider's live updates here.)

A recent study published in the New England Journal of Medicine suggested that "children might be less likely to become infected or, if infected, may show milder symptoms" than adults.

A girl wearing a face mask at Beijing's central railway station. Kevin Frayer/Getty Images

A few cases of the virus among children have been reported in the past two weeks, however. On January 26, a 9-month-old girl was diagnosed in Beijing. Days later, a child in Germany whose father was diagnosed with the coronavirus tested positive.

On Tuesday, health officials in China's Guizhou province reported that a 1-month-old infant had been diagnosed with the virus there.

Still, the coronavirus seems to primarily affect an older population. In a recent study of 99 people with the coronavirus, their average age was 55.5. Another study reported that the median age of 17 people who had died was about 75. Many of those people had other health issues like high blood pressure, diabetes, or Parkinson's disease.

Aria Bendix and Hilary Brueck contributed reporting to this story.