That announcement comes amid a rush of developments surrounding the outbreak, including: reports of a potential vaccine, a shift in the majority of new cases to nations outside of China for the first time, the emergence of cases in California and Germany with no obvious source of transmission, the monthlong closure of Japanese schools, and the continued decline in global financial markets over economic downturn fears.

Public health officials, however, have expressed cautious optimism over evidence that China's drastic control measures, such as strict travel restrictions, lockdown of some cities, and the closure of factories, businesses, and schools, seem to have been effective.