SARS Virus May Be a Hybrid

Researchers have found that the coronavirus that causes severe acute respiratory syndrome (SARS) is formed from genetic material that may have resulted from the combination of mammalian and avian viruses.

Investigators at the University of Toronto (Canada) used Bayesian, neighbor-joining, and split decomposition phylogenetic techniques on the SARS virus replicase, surface spike, matrix, and nucleocapsid proteins to examine the evolutionary origin of the SARS coronavirus.

They reported in the January 2004 issue of the Journal of Virology that the replicase protein was of mammalian-like origin, the matrix and nucleocapsid proteins were of avian-like origin, and the host-determining spike protein was of a mammalian-avian mosaic origin.

It is believed the virus was transmitted to humans by masked palm civets (an animal related to ferrets and cats) in the food markets of southern China. "It is possible that a civet picked up the virus from a bird,” explained senior author Dr. David Guttman, professor of evolutionary genomics at the University of Toronto. "This could have created the opportunity for a very rare recombination event that produced a virus with a new host range. These recombination events have the potential to create an entirely new structure essentially instantaneously. Since our immune systems have never seen this new viral form, it is more difficult for them to respond to it in a timely and effective manner.”



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