“The discovery in Chinese horseshoe bats of the widespread presence of a SARS coronavirus-like virus, with a high degree of genetic relatedness to the civet or human SARS coronavirus, suggests that bats could be the natural reservoir of this type of virus.”

The SARS (severe acute respiratory syndrome) epidemic is the first pandemic linked to a newly emerging viral respiratory disease in the new millennium. About 8,000 people have been affected, with a fatality rate of 15%. The scientific world is profoundly interested in probing the origin of the virus.

The paper describes a novel bat SARS coronavirus and the complete genome sequences of three strains of the virus which were collected at various times and locations. The seroprevalence using enzyme immunoassay for nucleoprotein or neutralizing antibody were found to be highest amongst Chinese horseshoe bats or Rhinolophus sinicus. The viral load in the anal swabs of these bats can go up to 7 log by quantitative PCR.

The paper tries to search for the origin of the SARS virus, which may have major implications if a resurgence of such epidemics occurs. The discovery in Chinese horseshoe bats of the widespread presence of a SARS coronavirus-like virus, with a high degree of genetic relatedness to the civet or human SARS coronavirus, suggests that bats could be the natural reservoir of this type of virus.

I had the privilege of seeing the first case of SARS in the Hong Kong Special Administrative Region of China. From the lung tissue of a relative of this first indexed case, we grew the SARS coronavirus. We then designed diagnostic testing using RT-PCR, Light Cycler PCR for viral load and immunofluorescent antibody assays, for the prospective study of a large cohort of patients. Thus we were able to describe the clinical progression of this disease in humans.

Because the early cases of SARS were chefs and animal slaughterers, we therefore tried to find the animal hosts in the wildlife markets on the Mainland. We also tried to establish that the seroprevalence is higher among those who were exposed in the markets, when compared with the normal controls.

A caged civet cat in the market turned out to be the host, but none of the civets in the wild or farms were found to be carrying the virus. Thus, the caged civets are merely just amplification hosts.

We then set out to find the introductory host or natural reservoir. In one of the water tunnels, 16 km from the wildlife market, we found that the Chinese horseshoe bats there were carrying the virus.

Bats and other wild animals are consumed as delicacies throughout Southern China, a habit whose origin has a long cultural history. The presence of such potentially dangerous viruses in these animals has a few important lessons.

Firstly, we should protect rather than consume such wild animals, with a primary importance being placed on biodiversity. Secondly, biosecurity must be established if we allow farms to continue to rear civets or other wild animals. Thirdly, they should be centrally slaughtered and frozen for sale, instead of putting them in open-air markets, where a mixing of different animal species may lead to genetic changes as a result of facilitated interspecies mingling.

In fact, the government of China has finally banned the sale of civets and closed down the wildlife markets.