But just how deadly is the new virus and how anxious should we be? While it's too early to tell if this latest threat will prove as deadly, health authorities are drawing on lessons from that grim past.
China has stepped up measures to contain the virus that has killed 25 people and infected more than 800.
In the United Kingdom, the BBC reports 14 people have been tested for the coronavirus. How that transference happened, and what animals the virus sprang from, remain unknown.
All but one of the 18 deaths have been in Hubei, but there are more than 600 cases, including several overseas.
The Center for Disease Control has issued advisories asking people to curtail unnecessary travel to areas in China where the virus is present.
However, this coronavirus is a strain which has never before been detected.
Hospitals across the US routinely go through drills to prepare for highly infectious diseases, as was the case at the hospital in Everett just weeks before the first coronavirus patient arrived.
Uber sells Indian Eats business to Zomato in move to cut losses
The Zomato and Uber Eats combine will change the dynamics even further by giving Zomato's user base a big boost. Facing stiff competition from Zomato and Swiggy, Uber Eats had been making losses.
That is what researchers are now trying to figure out: whether or not the virus can spread from human to human, and how contagious it is.
Complicating matters, if this new virus is fairly mild, it may be harder to stem the spread. If infection with the 2019 coronavirus is confirmed, DPH will work closely with the CDC and local partners to reach out to people who came in close contact with the person on the airline flights. Nor is there any way to know yet how often people become infected but show no obvious symptoms.
Buzyn said she had no information yet on the second case, in Paris, which had just been confirmed.
"This is why we need to rely on self-monitoring", Cetron said.
In response to the spread of the virus, airports worldwide have stepped up screening of passengers arriving from China, conducting temperature checks that would indicate fever and looking for other symptoms, including cough and difficulty breathing. There is one, but health authorities in China, the USA and elsewhere are working to make it more widely available.
The World Health Organisation surprised many on Thursday by announcing they are not now classing the virus as an "international emergency".
Both the USA cases returned to the country before the screening began. He had diarrhea for three days and visited a doctor at a hospital.
Right now, there are no vaccines that can prevent the transmission of this coronavirus, though the CDC said Tuesday that there are "active conversations" going on with the National Institutes of Health about developing a vaccine.