LITTLE KNOWN ABOUT VIRUS ITSELFChinese health authorities are still trying to determine the origin of the virus, which has been linked to a seafood market in Wuhan. They have confirmed human-to-human transmission and that 15 medical staff in the country have been infected.The WHO says an animal source appears most likely to be the primary source of the outbreak. COUNTER-MEASURESThere is no vaccine for the new virus.Chinese authorities have stepped up monitoring and disinfection efforts ahead of the Lunar New Year holiday in late January, when many of China's 1.4 billion people will travel domestically and overseas.Airport authorities in the United States as well as many Asian countries, including Japan, Thailand, Singapore and South Korea, stepped up screening of passengers from Wuhan.Singapore announced on Jan. 21 that it will quarantine individuals with pneumonia and travel history to Wuhan within 14 days before the onset of symptoms.The WHO sent directives to hospitals around the world on infection prevention and control. It has also convened an emergency committee of experts on Jan. 22 to assess whether the outbreak constitutes an international emergency.