Contaminated drinking water, usually associated with poor and developing nations, is likely to become more of a hazard in the wealthier parts of the world in the next few decades, a group of microbiologists warned last week.

As demand for water grows, many decrepit supply systems are unable to take the extra strain. As a result, the water reaching homes and businesses could soon be laden with pathogens, says a report from the American Academy of Microbiology. "The distribution of safe water to home can no loner be taken for granted, not even in the US or Western Europe," it says.

"There is a crisis looming in the whole area of waterborne disease," says Timothy Ford of Harvard School of Public Heath, one of the report's authors.

The microbiologists warn that the list of pathogens that can be transmitted in contaminated water is "increasing significantly each year". Worse, scientists have recently identified strains of waterborne pathogens—including Cryptosporidium, giardia and cyclospora—that show signs of resistance to the chemicals used in water treatment and disinfection.

People living in industrialized counties are poorly prepared for the coming threat. Unchallenged by such infections for so long, people have little immunity to waterborne pathogens and so are at greater risk of contracting diseases when the system breaks down. The number of people with weakened immune system is likely to grow because of the aging population and the increase in cancers and AIDS, says Ford.

Added to this, there is very possibility that some strains of pathogen will have become so resistant to antibiotics that they could be untreatable.

The microbiologists stress the need to identify more "indicator" organisms, microorganisms which signal the presence of harmful pathogens. Currently, treatment plants tend to rely on the presence of coliform bacteria such as Escherichia coli as a sign that the water is contaminated with faecal matter—and presumably pathogens.

But coliform bacteria are not reliable indicators of other types of harmful organism such as viruses or protozoa. "New method for pathogenic bacteria, viruses and protozoa are badly needed," says the report.