An unknown strain of pneumonia has been making people ill in Wuhan, China. 44 people have been infected with the unidentified virus, with 11 of them in a serious condition.
The local government and health authorities have been able to rule out Avian flu, influenza and adenovirus infection.
Many of the patients worked at a seafood market that also traded in live animals like rabbits and birds which has prompted some concerns about a return of the deadly 2002 Sars virus.
While Sars hasn't yet been ruled out, there is no evidence of human-to-human transmission and no medical personnel have become infected.