The next day, she developed a fever and began sneezing. She was admitted to Hechi People’s Hospital and put in isolation, officials said. Officials did not disclose who she was traveling with or what condition they might be in.

Medical experts are watching closely to see who the coronavirus infects and who might be most vulnerable to it. Most of those killed by the coronavirus so far have been older men, many with chronic health issues. The youngest fatality disclosed so far was 36 years old.

Another doctor collapses and dies of heart failure.

State news media reported on Saturday that a doctor had died of a heart failure while tending to patients with the coronavirus in fever wards at a hospital in eastern China. It was unclear whether he had showed signs of the virus.

The doctor, Jiang Jianjun, who specialized in infectious diseases, suffered the heart attack on Thursday while making rounds at the fever wards in Jiangsu Taizhou People’s Hospital, according to an online tribute posted on the hospital’s social media account.

“He collapsed at his beloved workplace,” the statement read. It has since been deleted, but it said that Dr. Jiang had also treated patients during the outbreaks of the avian flu and swine flu.

News of his death, along with that of a retired physician in Wuhan who was suspected of having the virus, drew much sympathy online, even as frustration brewed over the crowds at hospitals and the shortage of supplies. Several internet users questioned whether Dr. Jiang had died of fatigue.

As footage and photos appeared to show medical workers in white coats wailing from the stress of working several consecutive shifts, many social media users used forums to accuse the government of failing to provide adequate support to physicians working on the front lines of the outbreak.