The number of cases of a novel virus in China has escalated sharply, with authorities in the city of Wuhan now reporting nearly 200 people infected, an increase of 136 over the weekend. Authorities also reported an additional death tied to the virus, bringing the total number of fatalities to three.
The mushrooming in the number of cases, along with confirmation of two cases in Beijing and one in Shenzhen adds to evidence that the virus — a coronavirus, from the family that also includes SARS and MERS — can be transmitted from person to person.
In a statement, the World Health Organization said “there is evidence of limited human-to-human transmission.”
“While currently there is no clear evidence of sustained human-to-human transmission, we do not have enough evidence to evaluate the full extent of human-to-human transmission,” the WHO said. “This is one of the issues that WHO is monitoring closely.”
Health authorities had previously tied most cases to a large seafood market in Wuhan — located in central China — that also sold the meat of various animals. But Matthew Frieman, a coronavirus expert at the University of Maryland, said human transmission likely accounts for at least some of the increase in cases.
Neil Ferguson, an infectious diseases epidemiologist at Imperial College London, agreed.
“The latest press release from Wuhan is quite non-specific about how these people were exposed,” Ferguson said. “But one would think that if they have clear sources of exposure to markets in all of those cases, they would have said so.”
China first reported the outbreak to the World Health Organization on Dec. 31. Initially, authorities in Wuhan appeared to suggest new infections had stopped after the closure of the Huanan Seafood Market. But new cases of the virus, which causes pneumonia, make clear that the outbreak is ongoing.
On Sunday, authorities in Shenzhen, a city in Guangdong province, confirmed a case, a 66-year-old man who had visited Wuhan on Dec. 29 and became ill on Jan. 3. That discovery came after Thailand reported two cases and Japan diagnosed one — all in tourists or nationals who had come from or visited Wuhan.
Finding cases elsewhere in China is to be expected at this point, said Ferguson, who released a modeling study late last week that suggested that there may have been hundreds of infections at this point.
“If three cases have been exported internationally there are bound to be cases in other cities in China. It’s really just a matter of time until cases are detected,” he said.
With the Chinese New Year fast approaching — it is Jan. 25 — there are grave concerns the new virus will spread rapidly. The holiday involves massive internal travel, a fact that could make watching for respiratory infections in people who have been to Wuhan an increasingly ineffective way to monitor for spread of the virus.
On Friday, the Centers for Disease Control and Prevention announced it would begin screening passengers arriving from Wuhan at San Francisco, Los Angeles, and John F. Kennedy Airport in New York, looking for signs of respiratory infections.
“There are going to be lots more cases as testing catches up. All over China and neighboring countries,” Frieman said. “I think that with the massive travel coming up for the lunar New Year it’s pretty scary.”
“And we will see cases in the U.S. from travel,” he added. “I also suspect the cases will get through airport screeners and show up in community hospitals. I don’t know what happens then.”
Much is still unknown about this virus, with no word yet of what animal or animals spread it to people.
Most infections seem to cause relatively mild illness, though in some cases people become gravely ill. Of the 198 cases detected in Wuhan, 170 are still in hospital. Of those, 35 cases are considered severe and nine are in critical condition.