The WHO conference on SARS in Malaysia has just ended with warnings to remain vigilant because SARS could re-emerge and the animal reservoir is not well defined. The SARS epidemic is about to enter the 2nd 100 days since WHO issued its alert, but it is not clear that officials are paying attention.
SARS is not going to re-emerge from the wilds of Guangdong Province from some exotic animal. SARS is right here in River City, complete with a strong set of deletion and point mutations.
SARS emergence from wild animals in Guangdong Province was a rare event. The SARS coronavirus quickly lost 29 nt of information and now 17 of 18 isolates have this deletion. Those with the deletion include isolates from Beijing and Shenzhen in mainland China as well as isolates from patients in Toronto, Bangkok, Singapore, Hong Kong, and Frankfurt. Most of these isolates are linked to the Metropole Hotel and have all 7 of the Metropole Hotel mutations.
The data just released from the Canadian National labs in Winnipeg confirms the early data which showed evidence for the SARS coronavirus in probable and suspect cases as well as patients with symptoms who failed to meet the WHO case definition for suspect or probable cases. Many of their contacts were not interviewed or even identified. Investigators in Toronto as well as Hong Kong are now going back to do more widespread tracing on patients positive for the virus to better understand how far and wide the virus has spread.
The finding of evidence of the SARS virus in patients with a broad spectrum of symptoms suggests the virus has spread quite widely. Molecular epidemiology can help trace the virus as well as mutations. It seems highly unlikely that the 29 nt deletion will be restored and it also seems unlikely that the various point mutations will go away.
In the fall, when flu and cold season returns, the SARS symptoms will be masked by flu and cold symptoms as well as unrelated cases of atypical pneumonia. Co-infection of patients with coronaviruses such as 229E or OC43 and SARS coronavirus will also provide opportunities for novel recombinants. Such recombinants with the infectivity of a cold virus and the potential for causing a fatal pneumonia would represent a formidable challenge.
The mutated SARS coronaviruses are the reservoir of concern for SARS, and the reservoir is right here in River City.