SARS was first recognized in Guangdong Province, China in November of 2002. It then spread extremely rapidly to other regions within China, Hong Kong, Vietnam, Singapore, Taiwan, and Toronto, Canada in the early half of 2003.
SARS is characterized by severe, pneumonia-like symptoms which can be fatal. SARS-CoV was transmitted from person to person mainly through respiratory droplets produced when a person sneezes or coughs and through direct contact with a surface contaminated with infected respiratory droplets.
Altogether, more than 8,000 people were documented to have been infected with SARS-CoV and over 800 died.
The global scientific response to SARS was unprecedented. Within weeks after the respiratory disease was first reported, the agent that causes the disease was identified, diagnostic tests were developed, and the entire genome of the virus was sequenced.
Epidemiologists gathered evidence that the first people infected had had contact with wild game in the markets of Guangdong Province in China. It is likely that these individuals were infected through direct contact with infected animals, particularly palm civets, which harbored very closely related coronaviruses. The virus then is thought to have mutated to adapt to its human host, and consequently human-to-human transmission became more efficient, setting off the SARS epidemic.
Fortunately, the SARS outbreak was short-lived, and public health containment procedures and coordinated responses proved effective in preventing further spread of the disease.
Until recently, SARS-CoV was the only member of the coronavirus family known to cause death or severe respiratory disease in humans. The other previously known viruses in this group cause mild upper-respiratory infections in humans and are associated with respiratory, gastrointestinal, and neurologic diseases in animals.
One reason that SARS-CoV might have been more lethal than other coronaviruses is that it appears to interfere with an enzyme system in humans that is critical for regulating body fluid balance. Therefore, the virus could disrupt normal functioning of the lungs by blocking this enzyme system and allowing fluid to leak into the air sacs of the lungs, resulting in severe respiratory illness.