Updated on Jan. 17 at 2 p.m.
Three U.S. airports will begin screening passengers from Wuhan, China, for symptoms of the new strain of coronavirus — named 2019-nCoV — that has been discovered in China.
Health officials in China say the virus is the culprit in a pneumonia outbreak in the central city of Wuhan, where more than 40 people have been diagnosed with mysterious viral lung infections since early December. Two cases have been identified in Thailand and one in Japan from travelers who had recently come from Wuhan. Two deaths have been reported in Wuhan.
The Centers for Disease Control and Prevention made the announcement on Friday. Screening for symptoms will begin when direct flights from Wuhan arrive at JFK in New York on Friday night and at San Francisco's SFO on Saturday. The third airport, LAX in Los Angeles, does not have direct flights landing from Wuhan but will screen arriving passengers who initially flew out of Wuhan.
The outbreak was announced in China on Dec. 31. Chinese researchers say they sequenced the new coronavirus's genome from one patient's samples and matched it to others in the outbreak.
Some, but not all, of the cases appear to be linked to a large seafood market in the city, which also sells live animals for meat. Experts think the infection probably came from people touching or eating animals that carry the virus. These individuals then developed viral symptoms including fever, breathing issues and lesions on their lungs.
The coronavirus family includes six other strains known to infect humans. All share a signature look under a strong microscope: a circle with spikes coming off the surface, ending with small blobs — hence the "corona."
"Kind of looks like the peaks of a crown," says Carolyn Machamer, a virologist and cell biologist at The Johns Hopkins University School of Medicine.
Four of those strains cause common colds, and two — SARS and MERS — have caused major pandemics. So how concerned should you be about this new disease?
Virologists watching the outbreak are asking three main questions to assess the severity of this coronavirus, on the scale of sniffles to severe threat.
1) Is it contagious?
Chinese authorities say the virus does not transmit easily between people.
Since health workers treating patients don't seem to have fallen sick, it's reasonable to believe that the virus doesn't spread efficiently, says Vineet Menachery, a virologist at the University of Texas Medical Branch at Galveston.
The ease of person-to-person spread rests on several factors, including how well the virus replicates in a person and where in the body the infection is located.
"If it's in the nose or the upper airways, it potentially could be breathed or coughed out easier" compared with a deeper lung infection, says Matthew Frieman, a virologist at the University of Maryland School of Medicine.
The SARS virus spread readily through close person-to-person contact. The SARS pandemic originated in southern China in 2002, infected more than 8,000 people globally and caused some 800 deaths before the outbreak ended the following year.
MERS, which emerged in 2012 in Saudi Arabia, appears to spread less easily between people but to be more lethal. To date, it has infected around 2,500 people and caused around 850 deaths.
2) Is it lethal?
Chinese health authorities have reported two deaths from the virus in Wuhan: a 61-year-old man, described as a frequent visitor to the market, died last week, and a 69-year-old man, who became ill on New Year's Eve, died Wednesday.
About a half-dozen patients were in critical condition. Other patients have been treated and discharged.
The fact that people seem able to fight off the infection and recover is a good sign, says Machamer of Johns Hopkins.
"It's a serious-enough infection, but not like SARS or MERS," she says.
Health authorities are monitoring the patients in Wuhan and their close contacts to help manage the outbreak.
3) Is it contained?
So far, three cases of coronavirus have been confirmed outside of China, in travelers from Wuhan. Two Chinese tourists in Thailand and a Japanese man who returned from a trip to Wuhan were all confirmed to have the coronavirus. The World Health Organization says it's "not unexpected" for cases to be found elsewhere and called on other countries to monitor for signs.
Earlier this month, authorities closed the seafood and live animal market linked to the pneumonia cases for cleaning and investigations. It's a step from the post-SARS playbook on containing outbreaks.
"Viruses that emerge from animals need some time to become an epidemic strain," says Menachery. "The faster you find them, the faster you limit the spread."
He says that closing live animal markets in China and implementing strict quarantine procedures helped end the SARS outbreak globally.
CDC emphasizes that the risk of spread to the general American public is low but it will add about 100 staff to the three U.S. airports where screening will take place at its quarantine stations. Specimens will be collected from suspected cases and sent to CDC to confirm the diagnosis.
As more information about the virus comes to light, CDC says it will "reassess entry screening measures and could scale activities up or down accordingly."
On the "scared or not scared" scale, Frieman says his concern level for this outbreak is 4 out of 10. Signs point to an infection that's not very lethal and doesn't spread easily between people.
But until the source of the infection is found, there's no guarantee that the problem has been contained.
Several of the cases appear to be in people who did not visit the market that was closed, suggesting that animals from the same infected population may have been sold at other live markets or that, in some cases, it can spread between people.
If the number of cases increase, or more people start dying, he'll worry more. And if the virus shows signs of mutating and becomes easily transmitted between people, he says, virologists will become very concerned — that's a historic warning sign for pandemics.