Infectious disease experts are keeping a close eye on a mysterious outbreak of pneumonia in central China that's sickened more than three dozen people, reports Bloomberg.
As of Jan. 3, 44 pneumonia cases have been confirmed in Wuhan, China, according to a statement from the city's health agency cited by the publication.
The World Health Organization is working with the Chinese government to investigate the outbreak. Health officials have ruled out common respiratory illnesses like the flu, but the exact cause of the illness is still unknown.
Several of the sickened individuals worked at a local market that sold animals like birds and pheasants. This detail is prompting concerns that an unknown animal virus may have spread to humans, reminiscent of the 2003 SARS outbreak, which killed nearly 800 people.