Sars ‘here to stay’

The Sars virus could pose a threat to humans for many years to come, research suggests. Scientists have compared samples of the virus from Singapore with samples from other countries where it has struck.

The Sars virus could pose a threat to humans for many years to come, research suggests. Scientists have compared samples of the virus from Singapore with samples from other countries where it has struck. They have found that the main components of the virus have remained unchanged as infection has spread across different countries. Experts had hoped that the virus would behave in the same way as similar viruses that have caused serious flu epidemics in the past. These viruses ceased to be a threat after their DNA mutated into a less dangerous form. But the latest analysis suggests that the Sars virus is not changing – and thus is unlikely to mutate into a less dangerous form in the foreseeable future. Scientists have identified the virus that causes Sars as a new member of the Corona family. It has been dubbed Sars-CoV. Usually human coronaviruses have a high rate of genetic mutation which can lead to new strains. Researchers led by Dr Edison Liu, from Singapore’s Genome Institute, studied the genetic make-up of cultured Sars viruses from five different sources. They found only a handful of mutation differences between the samples – and it was thought these probably resulted from the virus adapting to laboratory conditions. The findings were published in an on-line report from the Lancet medical journal. In an accompanying commentary, two Canadian experts warned of the implications. Early Brown and Jason Tetro, from the University of Ottawa, said: “The results suggest a remarkable genetic conservation of the virus since the outbreak was first documented. “Unfortunately, this conclusion means that Sars-CoV is not likely to change rapidly and thus may not readily mutate to a benign infection, as is the hoped-for eventuality seen in most other epidemics.” Lung damage A separate study, also published on The Lancet website, concludes that much of the lung damage associated with Sars is in fact caused by the body’s own response to infection. Researchers from the University of Hong Kong found a common pattern of illness among 75 patients who were admitted to hospital following an outbreak of Sars at Amoy Garden, a Hong Kong high-rise housing estate. For the first week after admission, symptoms gradually improved, but a deterioration set in during the second week of the hospital stay. Some 85% of the patients developed recurrent fever after nine days. This delayed deterioration suggests that damage is being inflicted on the lungs not by the continued spread of the virus, but by an overblown immune response. (Source: BBC, Thursday, 8 May, 2003, 23:00 GMT 00:00 UK)