Severe Acute Respiratory Syndrome (SARS) first emerged in humans in China in early February. Since then there have been more than 200 reported fatalities in nearly 5000 cases.
While the World Health Organization originally cited the death rate for SARS to be about four percent, experts now worry that statistic may be unreliable. The most recent statistic reported by Hong Kong, Canada, and Singapore (three of the hardest hit places) set the death rates at 7.6, 10.7, and 9.9 percent respectively. The revision for the SARS fatality rate, likely at approximately 10 percent, puts the disease on par with viruses such as yellow fever and Japanese encephalitis.
Recent studies show that SARS is caused by a coronavirus, which has not been involved in any previous outbreaks. Studies in monkey performed in the Netherlands showed that the new coronavirus alone was sufficient to cause SARS.
There are 10 known coronaviruses, which affect mammals, two of which are responsible for common colds. However, a great number of coronaviruses are still unknown. The virus responsible for SARS is believed to be distantly related to a mouse coronavirus and avian coronavirus. Coronaviruses undergo a process known as recombination, where they swap material with each other. The resultant virus is genetically similar to its parents but may contain capabilities.
According to virologist Shinji Makino of the University of Texas Medical Branch in Galveston, the SARS virus may have likely long been able to infect people. If this is the case then it only recently encountered conditions which allowed it to spread. On the other hand, the virus could be derived from unidentified animal coronaviruses which only recently mutated to a human virus.
Despite these problems, research continues. Recently, Chinese researchers who sequenced the virus reported a sequence considerably different from that of current information, indicating that the virus mutates rapidly.
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