UNCERTAINTY surrounds the identity of the virus responsible for the 鈥渟uper-pneumonia鈥� cases around the world, with two candidates emerging. But that has not prevented a basic test for the disease being developed.
Malik Peiris鈥檚 team at the University of Hong Kong has managed to grow a virus isolated from a patient with 鈥渟evere acute respiratory syndrome鈥� or SARS. It looks like a coronavirus, a family that includes some viruses that cause colds. The Centers for Disease Control in the US has also identified a previously unrecognised virus from the same family in SARS patients.
But earlier this week, labs in Germany, Taiwan and Hong Kong reported finding a paramyxovirus, a family that includes the viruses responsible for mumps and measles. The Canadian National Microbiology Laboratory in Winnipeg, Manitoba, went further, saying the virus was a subtype called human metapneumovirus. This is known to cause respiratory disease, but past cases have been far less serious than SARS. If hMPV causes SARS, it must have evolved into a more dangerous form. Alternatively, an animal metapneumovirus may have jumped the species barrier.
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The conflicting reports could both be right: a coronavirus and a paramyxovirus may together cause SARS. Such an interaction is unusual, but not unheard of. For instance, delta hepatitis, a rare but particularly unpleasant form of hepatitis, requires infection with both hepatitis D and hepatitis B.
鈥淔inding one virus doesn鈥檛 necessarily exclude a role for the other,鈥� says Peiris. 鈥淲e鈥檙e in the very early stages of understanding SARS and we haven鈥檛 seen anything like it before, so we have to keep an open mind.鈥�
Even though the virus鈥檚 identity remains uncertain, Peiris鈥檚 team has managed to develop a simple test that detects the antibodies that bind to the virus in the blood of people with SARS. The test is still being validated, but the hope is that it could be used to look for the antibodies in people who may have had the disease but have now recovered, in an attempt to track the spread of SARS.
Such a test could play an important role in ongoing investigations in China, where around 300 people in Guangdong province went down with severe pneumonia before SARS started spreading worldwide. It is not yet clear if the same virus is responsible for both outbreaks.
SARS is characterised by high fever, coughing and shortness of breath, often followed by pneumonia. There is no specific treatment. It鈥檚 thought that close, sustained contact with a patient is needed for infection to occur.
