23 April 2003 15:00 GMT

by Henry Nicholls

It looks like it's safe to go back in the water. A very short list of bacterial indicators turn out to be surprisingly good at predicting the illnesses that could result from swimming in sewage-infested waters, say microbiologists, and are all that is needed for the first health-based legislation on the quality of the world's bathing waters.

The quality of water at swimming beaches or rivers around the world is currently unregulated and subject solely to voluntary WHO guidelines. These standards were set in the light of decade-old research conducted at four UK beaches, where volunteers were coaxed into the water and monitored for subsequent illness. Now, the study has been replicated at five freshwater sites in Germany, and produced almost identical results.

"What's remarkable really is that the threshold of effect was identical," said David Kay of the Centre for Research into Environment and Health at the University of Wales, who carried out the original UK research. "We got almost the same answer in two different environments with populations 500 or 600 miles apart with very different cultural backgrounds," he said. "It's very rare, quite honestly, that any environmental epidemiology comes that close."

The two forms of bacteria - fecal coliforms and fecal streptococci - comprise numerous species present in sewage. However, it is unlikely that these are the organisms that are actually causing bathers to become sick. "Nobody's got a clue what's causing the illness," admitted Kay, who suggested that the onset and severity of symptoms presented by bathers was consistent with a norovirus.

"There are a lot of viruses present in the gut, in fecal material, and therefore in sewage," said Jane Sellwood, head of environmental virology at the UK's Health Protection Agency.

Whilst noroviruses are potential candidates for these illnesses, Sellwood suggests that something else is responsible. "Epidemiologically, the symptoms and the seasonality don't fit with the norovirus," she said. "We need the research to see what viruses are out there, but I don't think noroviruses have a place in routine monitoring," she told BioMedNet News.

Other virologists attending this year's 152nd meeting of the Society for General Microbiology, at which the UK and German results were reviewed, agreed that more research was needed on the viruses that might actually be causing these mild upsets. "They didn't actually say what they did in the way of virology," said Sheila Cameron of the West of Scotland Specialist Virology Centre in Glasgow. "I don't think the work's been done," she said. "There should be funding for research to do that."

But even in the absence of a causal link, Kay is confident that guidelines based on bacterial content are going to be helpful. "What we're suggesting is that it's a pretty robust threshold," he said. "It gives us quite a bit of confidence that The Word Health Organization ... has just about got it right."

A draft directive from the European Union that is based on the WHO guidelines would, if passed into law, make European waters the first worldwide to have their standards driven by a health-based measure.

Whilst Kay is confident that the UK and German studies provide a sound basis for setting standards in waters across Europe, he does not think that they should be applied worldwide without more work. "We're ... keen to see further epidemiology," he said.

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