Family tree of the common cold

The genomes of all known strains of human rhinovirus (HRV), responsible for the common cold, have now been sequenced.

Over a dozen strains from the 99 serotypes in the reference repository have already been sequenced, but now researchers from the universities of Maryland and Wisconsin in the US have sequenced 80 of the reference genomes and 10 additional field samples.

They found that new strains are sometimes the result of RNA recombination, which was not thought probable in the past, and that a hypervariable leader sequence may affect virulence.

They also found a potential fourth species of HRV. The viruses are usually grouped into HRV-A, with 74 serotypes, and HRV-B, with 25. New strains have recently been grouped into an HRV-C species, but now the researchers have found an unusual group of distinct strains within HRV-A that might actually be a different species, HRV-D.

They are cautious about doing so without further study, but say several sequence motifs are highly suggestive of a new species.

The study is published online in advance of publication in Science.

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