New China virus details show challenge for outbreak control

This virus was identified as cause of an outbreak of respiratory illness first detected in Wuhan, China. 

It can spre person to person, even if someone is showing symptoms. next in line can continue to pass it on. incubation period is so long that people may t kw where or when y picked it up.

Details that emerged last week about new virus from China show how challenging it could be to control this outbreak, health experts say.

At first, some were relieved that virus hasn’t proved fatal as often as those that caused SARS, Ebola or some or recent menaces. w re’s a worry that it still might cause a lot of deaths if it spres far more than those or viruses did.

“ level of concern has been growing” with new revelations about viral spre, said Marc Lipsitch of Harvard’s School of Public Health.

virus has infected at least 14,000 people since it was first detected in central China in late December. It has killed more than 300 and spre to about two dozen countries although most, like United States, have few cases.

“We still have a low risk to American public, but we want to keep it at a low risk,” National Institutes of Health’s infectious disease chief, Dr Anthony Fauci, said Friday at a news conference where quarantines and temporary travel bans were anunced.

Several factors about virus itself affect how b outbreak might become.

MULTIPLYING INFECTIONS

Based on first 425 confirmed cases in China, each infection led to 2.2 ors on aver, Chinese scientists reported last week in New England Journal of Medicine. That’s a bit more than ordinary flu but less than SARS, a genetic cousin of new virus.

“It sounds and looks as if it’s going to be a very highly transmissible virus,” said Robert Webster, an infectious disease expert at St. Jude Children’s Research Hospital who has studied many outbreaks.

Wher new virus will weaken as it spres or inste become better at it isn’t kwn.

“This virus may still be learning what it can do,” Webster said. “We don’t kw its full potential yet.”

SPREING IN STEALTH

biggest worry is sustained transmission, where one person spres virus to ar and that person continues to pass it on. A related concern is how often people with symptoms are infecting ors.

On Thursday, scientists reported that a Chinese woman who was t ill at time spre virus to a man in Germany during a business trip re, and that he in turn infected several or coworkers before showing any symptoms. A child of one of workers also is infected w.

This so-called asymptomatic transmission “puts a terrible burden on screening process,” which has heavily relied on symptoms to detect cases and track close contacts to limit spre, Fauci said.

If virus can move extensively from person to person or without causing symptoms, “it will spre furr and perhaps for longer than we initially hoped,” said Dr. Ashish Jha, a Harvard University global health professor.

DEATH RATE

mortality rate looks like 2% to 3% but could be much lower if many mild cases or infections with symptoms are going undetected, Fauci said.

SARS proved fatal in about 10% of cases. flu’s mortality rate is only 0.1%, yet it kills hundreds of thousands around world each year because it infects millions, Lipsitch ted. So size of outbreak can matter as much as lethality of virus in terms of how many deaths ultimately occur, he said.

INCUBATION PERIOD

Chinese scientists estimate aver incubation period to be roughly five days, but said it could last up to two weeks.

Such a long potential incubation period can be a problem, Webster said.

“People can move away from where y contracted it and t even remember” places where y may have been exposed, he said.

TESTING GAPS

It’s still a struggle to determine who is or is t infected. U.S. Centers for Disease Control and Prevention has a test, but lacks eugh confidence in its accuracy to make it widely available. Too little is kwn about possible methods -- throat or se swabs versus blood or or samples -- and how many false alarms or missed cases each might give at any point in time.

“If we h an absolutely accurate test that was very sensitive and very specific, n we could just test people and say, ‘OK, we’re good to go,’” Fauci said at news conference. “We don’t kw accuracy of this test.”

That leaves a key gap, Lipsitch said.

“Any factor that makes it harder to be sure if someone is a case or t makes control harder,” he said.