First appearing in Southern China in November of 2002, SARS (Severe acute respiratory syndrome) became a global threat by March, 2003. Spreading to more than two dozen countries in Asia, Europe, North America, and South America during the 2003 outbreak, SARS infected over 8000 people, killing more than 700.
SARS is caused by a coronavirus known as SARS-associated coronavirus (SARS-CoV). Coronaviruses are named for the halo or crown-like (corona) appearance that is seen when observed under a microscope. They are associated with mild to moderate upper respiratory illness in humans and are believed to be the cause of most instances of the common cold in adults. In animals, coronaviruses are known to cause respiratory, gastrointestinal, liver and nuerologic complications.
During the SARS outbreak, surveillance conducted in the live animal markets in Guangdong, China revealed SARS-CoV infection in masked palm civets (Paguma larvata), among other species, indicating that they could be the possible reservoir for the disease. This finding resulted in the culling of thousands of civets in hopes of preventing future SARS outbreaks. Subsequent studies, however, have revealed no widespread infection in wild or farmed civets. This, and the high viral prevalence in the market-tested civets, caused many to believe that civets were not the true wildlife reservoir. Although civets may have been the source of the human infection leading to the 2003 SARS outbreak, infection in this and other common species appears to have been the result of the crowded, live market conditions seen in Guangdong and other areas of China rather than an indication of the natural reservoir of the virus.
The presence of bats and bat products in food and traditional medicine markets in China led to the sampling of nine bat species in search of the natural SARS-CoV reservoir. From March, 2004 through December, 2004, investigators collected data from 408 bats representing 6 genera including Rousettus, 
Cynopterus, Myotis, Rhinolophus, Nyctalus, and Miniopterus. Bats were trapped in their native habitat at four locations - Guangdong, Guangxi, Hubei and Tianjin.
Among the species surveyed, 3 species from the genus Rhinolophus (horseshoe bats) demonstrated a high SARS-CoV antibody prevalence. The high seroprevalence and wide distribution of seropositive bats is consistent with the pattern of serology expected from a wildlife reservoir host for a pathogen. Complete sequencing of the virus, named SARS-like coronavirus isolate Rp3 (SL-CoV Rp3), revealed that the genome organization of this virus is essentially identical to the SARS virus associated with the 2003 outbreak (SARS CoV). Further evidence was found in the phylogeny of gene sequences from viruses in 5 bat samples. These sequences tightly group with the human and civet isolates of SARS coronaviruses.
The probability that there are still more SARS-related coronaviruses to be discovered in bats is high. Further studies in field epidemiology, laboratory infection, and receptor distribution and usage are being conducted to assess potential roles played by different bat species in the SARS emergence.
These findings suggest that there is a certain degree of genetic variability among coronaviruses in bats, thus increasing the possibility of spill-over events resulting in disease outbreaks in wildlife and human populations. It is therefore essential that we enhance our knowledge and understanding of reservoir hos
t distribution, animal-animal and human-animal interaction, particularly within the wet-market system, and virus genetic diversity of bat-borne viruses to prevent future outbreaks.
This study was a collaboration among scientists from the Consortium for Conservation Medicine (CCM); the Institute of Zoology at the Chinese Academy of Sciences (CAS), Beijing, China; the State Key Laboratory of Virology, Wuhan Institute of Virology, CAS, Wuhan, China; CSIRO Livestock Industries, Australian Animal Health Laboratory, Geelong, Australia; the Department of Primary Industries and Fisheries, Queensland, Australia; and the Guangzhou Institute of Biomedicine and Health, Guangzhou, China. Funding for the CCM component of the work is from an NIH/NSF “Ecology of Infectious Diseases” award from the John E. Fogarty International Center R01-TW05869 and core funding to the Consortium for Conservation Medicine from the V. Kann Rasmussen Foundation. This work is part of a collaboration between the CCM and the Australian Biosecurity Cooperative Research Center for Emerging Infectious Diseases (AB-CRC).
Relevant Links
CDC - Severe Acute Respiratory Syndrome