May 3
World Health Organization representatives arrive in Taiwan to assist local authorities trying to contain the island's SARS outbreak. On May 2, there were 100 SARS cases in Taiwan, almost triple the number reported 10 days earlier.

May 4
The WHO reports that the SARS virus can live up to four days in the waste from patients with diarrhea. But the WHO also finds that standard disinfectants such as chlorine bleach kills the virus in five minutes.

May 8
Taipei,Taiwan, China's northern city of Tianjin and the province Inner Mongolia join a list of SARS-affected regions that the WHO says people should avoid until the outbreaks have been contained. The list of places where people should postpone "all but essential travel" already includes Hong Kong, Beijing, and the Chinese provinces of Guangdong and Shanxi.

May 14
The WHO removes Toronto from its list of regions affected by SARS.

May 16
Taiwan's health chief resigns over a worsening SARS crisis that has infected 274 people. The government fills the slot with a U.S.-educated epidemiologist.

May 21
The WHO extends its travel advisory for the city of Taipei to include all of Taiwan, as the island's officials warn the outbreak has not peaked in the country's southern regions.

May 23
Responding to a Health Canada report of five probable SARS cases in the Toronto area, the Centers for Disease Control and Prevention reissued a travel alert for visitors to the city. The alert recommends that those traveling to the city take precautions to avoid becoming infected with the virus. Unlike a travel advisory, it does not recommend that people postpone trips to the city.

May 26
After Canada reported that it was investigating possible SARS cases in Toronto, the WHO put the city back on its list of areas where SARS is spreading. The WHO's spokesman says that the U.N. agency has no plans to reinstate a warning advising against travel to the city.