A new study has genetically linked the human SARS virus with one found in animals, a finding which suggests that the SARS-like virus jumped from animals to humans. The researchers, whose report was released online by Science Sept. 4, say the genome sequences had 99.8% homology to the novel coronavirus (SCoV) that causes SARS in humans. This indicates that the human and animal SCoV-like viruses are closely related.
The researchers studied 7 wild and 1 domestic animal species from different regions in southern China. The animals included civet cats, raccoon-dogs and ferret badgers. The study's 18 authors, from Hong Kong and Guangdong Province in China, noted that all the animal isolates retained a 29-nucleotide sequence, which is not found in most human isolates. They argued that the SCoV-like viruses found in these animals, many of which are sold for meat in China, may be the source of interspecies transmission. The researchers were quick to point out, however, that the animals studied may well have been infected by other animal sources, which remain unknown. They conclude that it is “not clear whether any one or more of these animals are the natural reservoir in the wild.”
Klaus Stöhr, head of World Health Organization's influenza program, says this study is important because it confirms that the SARS coronavirus exists outside of humans. However, he says additional cross-sectional studies are required.
Caroline Astell, projects leader for the Michael Smith Genome Sciences Centre in Vancouver, says many questions remain unanswered. “Where did SARS come from? What caused it to jump species? How will we tackle diagnosis and treatment?”
Astell says the study is a red flag. “China should be extremely cautious about lifting the ban on the sale of these animals.” — Allison Gandey, CMAJ