On 12 March, WHO issued a global alert about a new infectious disease of unknown origin in both Vietnam and Hong Kong. On 15 March, WHO issued a heightened global health alert about a mysterious pneumonia with a case definition of SARS after cases in Singapore and Canada were also identified. The alert included a rare emergency travel advisory to international travelers, healthcare professionals, and health authorities. The Centers for Disease Control (CDC) issued a travel advisory stating that persons considering travel to the affected areas in Asia (Hong Kong, Singapore, Vietnam, and China) should not go.
