GENEVA - The World Health Organization reports there is no evidence of human-to-human spread of the new coronavirus that has sickened dozens, but says the possibility cannot be ruled out.

Investigations are continuing, aimed at identifying the source of the new Coronavirus. Late last year, China reported a cluster of cases of pneumonia of unknown cause. Many were linked to a fish market in Wuhan, central China's largest city. The World Health Organization reports 41 people have been infected with the disease in China, including two deaths.

US to Screen Passengers at Airports for Signs of New China Virus Health officials at three US airports will screen travelers from China's central city of Wuhan

Additionally, two infections have been identified in Thailand and one in Japan among people who had traveled to Wuhan. The spread of the disease outside of China is raising concern among health officials and the general public.

Coronaviruses are a family of viruses that range from the common cold to MERS, Middle East Respiratory Syndrome, and SARS, Severe Acute Respiratory Syndrome. They can be spread from animals to humans, but also from human to human.

Maria Van Kerkhove, the head of WHO's Emerging Diseases and Zoonoses Unit, notes transmission between humans was limited during previous MERS and SARS outbreaks. However, she warns disease spread can be amplified, particularly in health care facilities.

"There is also the possibility of super-spreading events. The global community is very familiar with what happened with SARS in the past and this is something that is on our radar that is possible and what we need to prepare ourselves for," said Van Kerkhove.

The 2002-2003 SARS outbreak, which originated in China, infected more than 8,000 people globally and killed 774. Van Kerkhove says it is important to identify the pathogen and find the source of the outbreak, including the animal source.

"We need to better understand the modes of transmission. I mentioned the zoonotic transmission. So, how are people getting infected from a potential animal source," said Van Kerkhove. "And, is there any evidence of human-to-human transmission. From the information that we have, it is possible that there is limited human-to-human transmission, potentially among families. But it is very clear right now, that we have no sustained human-to-human transmission."

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A new scientific study in Britain indicates the coronavirus outbreak may be more serious than reported. The British experts report as many as 1,700 people may have been sickened by the disease, which can range from mild respiratory symptoms to severe disease and death.

International airports in the United States and a number of countries in Asia, including Hong Kong, Thailand, and Malaysia, have stepped up screening procedures of travelers coming from China.

The World Health Organization urges countries to be vigilant, but does not advise any travel restrictions.