An outbreak of severe acute respiratory syndrome (SARS) that hit China in March and April is over, according to the World Health Organization (WHO). In a May 18 announcement, WHO said the human-to-human transmission chain for the disease appears to be broken now that three weeks have passed since the last appearance of a new case. The WHO statement commends Chinese authorities for swift action in response to the SARS outbreak, saying their actions prove that this highly contagious, sometimes fatal respiratory disease is containable.The source of the outbreak remains a mystery for now. The infections occurred among workers at the National Institute of Virology in Beijing where some researchers had been working with live and inactivated SARS coronavirus as part of the international effort to learn more about the disease that first appeared in 2003.
