The novel coronavirus is now a "public health emergency of international concern," killing more than 1,600 people and infecting more than 69,000 worldwide.
Even worse: The US Centers for Disease Control and Prevention expects this virus to keep spreading beyond this year.
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Here's what makes this strain so unusual and what you can do to protect yourself.
Why is this coronavirus different?
There are many kinds of coronaviruses, including some that cause the common cold.
But this deadly strain is called a "novel" coronavirus because it has not previously been identified in humans.
It's unusual for several reasons:
-- Scientists believe this type of coronavirus jumped from a different animal to humans, which is rare.
-- It then became transmissible from human to human, which is even more rare.
-- An infected person might not show symptoms for up to 14 days after exposure. That's especially worrisome because this novel coronavirus can be transmitted while a person still isn't showing any symptoms.
What are the symptoms?
Fever, cough, runny nose, sore throat and trouble breathing are some of the most common symptoms of the novel coronavirus.
"It can be more severe for some persons and can lead to pneumonia or breathing difficulties," the World Health Organization says.
"More rarely, the disease can be fatal. Older people, and people with pre-existing medical conditions (such as diabetes and heart disease) appear to be more vulnerable to becoming severely ill with the virus."
How can you protect yourself?
In general, the public should do "what you do every cold and flu season," said Dr. John Wiesman, the health secretary in Washington state -- where the first US case of Wuhan coronavirus was confirmed.
That includes washing your hands often with soap and water for at least 20 seconds.
If you're the one feeling sick, cover your entire mouth and nose when you cough or sneeze. But don't use your hands. Use either your bent elbow or a tissue that you throw away immediately afterward.
WHO also recommends staying at least 3 feet or 1 meter away from anyone who may be infected.
Is there a cure for novel coronavirus?
No. Patients can be treated and may recover from their symptoms, but there is no known cure for the novel coronavirus yet.
What about a vaccine?
Scientists are working on a vaccine, but don't expect it anytime soon.
The US National Institutes of Health is trying to develop one, but says it will take at least a few months before clinical trials start and more than a year until a vaccine might actually become available.
Separately, scientists in Texas, New York and China are also trying to create a vaccine, said Dr. Peter Hotez, a vaccine scientist at Baylor College of Medicine in Houston.
But the challenge is daunting, Hotez said.
“The lesson we’ve learned is coronavirus infections are serious and one of the newest and biggest global health threats.”