A newborn baby in China has been diagnosed with the new coronavirus just 30 hours after birth, the youngest case recorded so far, state media said.

Doctors said the newborn's mother had tested positive for the virus before giving birth on February 2, reports various news media including Business Insider, BBC and China's state media Xinhua News. 

The case has raised speculations that the infection could spread from mother to infant in the womb, Business Insider reported.

State media outlet Xinhua reported news of the infection late yesterday and added that the baby, which weighed 3.25kg at birth (7lbs 2oz), was now in stable condition and under observation.

"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.

More than 28,000 people are now known to be infected nationwide in an outbreak that has killed 563 and spiraled into a global health emergency.