In May 2002 a mystery illness struck British soldiers in a field hospital at Bagram, Afghanistan, causing severe vomiting and diarrhoea in the camp - and consternation in a jittery press. Subsequently, tests showed this to be the non-fatal ‘winter vomiting’ virus that had swept the UK earlier that year. However, the harsh conditions faced by troops in Afghanistan, particularly the dehydration caused by the heat and altitude, gave sufferers particularly extreme symptoms. To prevent the fever spreading, hospital staff were quarantined and around 300 troops confined to their quarters.

The causative agents are enteric caliciviruses. "The problem with this virus infection," explains Professor Ian Clarke at the University of Southampton, "is you don’t know you’ve got it until you suddenly start vomiting." The illness, usually referred to as gastric flu, typically lasts for 24-48 hours and is characterised by projectile vomiting and diarrhoea. Viral gastroenteritis is the most common cause of gut infection in England, with an estimated 600 000-1 million cases a year - more than the total number of cases of Salmonella and Campylobacter. "It was originally called the winter vomiting disease because there was a peak incidence during the winter months," says Professor Clarke. Last year, however, the number of cases reported didn’t decline during the summer months; although the peak incidence is during the winter, sporadic outbreaks occur all year round.

The disease is spread when virus particles from an infected person get into the gut of another person, either through poor hygiene or when viral particles sent into the air after vomiting are inhaled and ingested. "That’s why the disease spreads so easily in ‘closed’ communities, like nursing homes, schools, hospitals and cruise ships," says Professor Clarke. "The virus is very stable so it readily contaminates enclosed environments. Immunity to the virus is not long-lasting therefore susceptible individuals can become infected from contaminated rooms that are not disinfected thoroughly."

With Wellcome Trust support, Professor Clarke and Dr Paul Lambden are collaborating with Professor Richard Elliot at the Division of Virology, University of Glasgow, to investigate the molecular biology and replication of the virus responsible for the illness. "One of the problems in understanding the biology and pathology of norovirus (see box below) infections is that this is one of the last remaining human viruses we can’t grow in continuous cell culture," he explains.

Since the virus only grows in enterocytes, the cells that line the gut and absorb nutrients and water into the body, Professor Clarke and his team are making a DNA copy, or clone, of the viral genome and testing it in bovine organ culture. "If the clone works - if it replicates itself in bovine gut tissue and produces a progeny viruses, as we expect it to do - we will introduce an antibiotic resistance marker, and try and force the clone to replicate in continuous cell lines." The antibiotic resistance marker will allow the team to select cells in which the virus is making new copies of its genome and hence replicating successfully. The teams will then be able to look at the genetic sequence of the clones and determine which mutations are required for adaptation to growth in standard laboratory cell lines.

See also

• Professor Ian Clarke at the University of Southampton: Research interests
• Dr Paul Lambden at the University of Southampton: Research interests
• Professor Richard Elliot at the University of Glasgow: Research interests