A new SARS-like virus has killed at least nine people in China, infected hundreds of others, and had already reached the United States.
Fears have been mounting that the virus will spread all through the massive annual Lunar New Year celebration. A host of Asian countries and the United States have added new screening assessments for passengers from the epicenter of the outbreak - Wuhan, China.
Here's what we know about the virus:
1. It's entirely new
The virus seems to be a never-before-seen coronavirus strain - a massive virus family that was linked to Severe Acute Respiratory Syndrome (SARS), which killed hundreds in mainland China and Hong Kong between 2002 and 2003.
Arnaud Fontanet, head of the department of epidemiology on the Institut Pasteur in Paris, told AFP the modern virus strain turned into 80 percent genetically identical to SARS.
China has already shared the genome sequencing of this novel coronavirus with the global medical community. For now, it is called "Novel coronavirus (2019-nCoV)."
China Central Television reported on January 9 that many of the people who had become ill tested positive for the new virus. Scientists in China shared the genetic sequence of the new virus two days after, and the WHO applauded China's efforts.
2. It's being passed among humans
The World Health Organization stated Monday it believed an animal source became the "main source" of the outbreak. The Wuhan government identified a seafood marketplace as the center of the epidemic.
But China confirmed that the virus is now passing from person to person - without going to Wuhan's marketplace.
Doctor Nathalie MacDermott of King's College London stated it seems possible that the virus is unfolded through droplets in the air from sneezing or coughing.
The spread of the virus - which estimated that there had been some 1,343 cases in Wuhan - is similar to a projection of 1,700 last week by Imperial College, London, according to doctors of the University of Hong Kong.
3. It is milder than SARS
The symptoms of novel coronavirus appear to be less aggressive compared to SARS, and professionals say the demise toll is still noticeably low.
At least 25 out of 200 people infected in Wuhan have already been discharged, according to local officials.
Zhong Nanshan, a renowned scientist at China's National Health Commission, said examining 2019-nCoV is challenging since the patient's lung condition is not always like SARS.
The seemingly milder virus is "paradoxically extra worrying" to humans as it allows humans to roam around before the signs and symptoms are detected, Professor Antoine Flahault of the Institute of Global Health on the University of Geneva, told AFP.
4. It could result in a global public health emergency
The World Health Organization (WHO) is set to hold an emergency meeting to address this novel virus that has been found in Thailand, Japan, and South Korea. The health agency would also tackle whether or not the outbreak constitutes a "public health emergency" and what needs to be done to control the virus.
The business enterprise has used the rare label a handful of times, including at some stage in the H1N1 - or swine flu - a pandemic of 2009 and the Ebola epidemic that devastated elements of West Africa from 2014 to 2016.
The Chinese government announced Tuesday it becomes classifying the outbreak inside the same category because of the SARS outbreak, meaning compulsory isolation for those identified with the disorder and the capability to implement quarantine measures on travel.
But if the WHO comes to a decision to take this step, it might place the Wuhan virus in the identical class as a handful of very severe epidemics.