March 5
Sui-chu Kwan, a 78-year-old Toronto woman who traveled to Hong Kong in February, dies of SARS.

March 10
China first approaches the WHO for assistance in investigating the cause of a mysterious pneumonia in Guangdong province.

Doctors report that 22 hospital workers in Hanoi are suffering from a mysterious illness similar to the one the World Health Organization's Dr. Carlos Urbani discovered in the same city.

March 11
An outbreak of what will be known as SARS is reported among Hong Kong hospital workers.

March 12
The WHO issues a global alert about cases of an atypical pneumonia with an unknown cause that poses a high risk to health care workers. The alert describes the symptoms of the mysterious flu-like illness. It also recommends doctors isolate patients with similar symptoms and report suspected cases to national health authorities.

By the time the WHO publishes its alert, its officials are already coordinating with national authorities in some affected regions, including Hong Kong where the Department of Health said in a statement that it is working "closely with WHO on disease control and prevention."

March 14
The U.S. Centers for Disease Control and Prevention activates its newly completed emergency operations center in response to the increasing number of SARS cases. At this point, the CDC has not yet identified any cases in the U.S.

March 15
The WHO issues an emergency travel advisory detailing the disease's symptoms and issuing instructions to airlines. In a statement, WHO Director General Dr. Gro Harlem Brundtland says, “This syndrome, SARS, is now a worldwide health threat. The world needs to work together to find its cause, cure the sick, and stop its spread.

Responding to WHO reports, the CDC issues a health alert to hospitals and clinicians, and briefs state health officials. The CDC also begins distributing cards warning of possible SARS exposure to passengers returning directly from Hong Kong.

While the WHO advisory does not recommend travelers avoid regions where SARS is spreading, the CDC advises that people planning "nonessential or elective" trips to affected areas "may wish to postpone their trip until further notice."

March 19
The CDC announces that it is investigating 11 possible cases of SARS in the U.S.

March 24
According to CDC scientists, research suggests the cause of SARS is a virus in the same family as the one that causes the common cold.

March 25
China bars the WHO from Guangdong province.

March 26
Chinese officials increase their tally of SARS patients from 305 to 792. A Chinese government spokeswoman says 31 people had died from the illness in the southern Guangdong province by late February, a marked increase from the number of deaths previously reported. The Chinese government also reports three additional people in Beijing died from the disease in March.

March 29
The CDC extends its SARS travel advisory to include all of mainland China as well as Hanoi, Vietnam and Singapore. The previous CDC travel advisory was for Hong Kong, China's Guangdong province and Hanoi.