Rainfall Runoff Illnesses*

Rainfall runoff linked to illnesses

August 1, 2001 Posted: 11:46 AM EDT (1546 GMT)

WASHINGTON (AP) -- In upstate New York two years ago, a severe storm at a county fair washed droppings from a barn into the water supply, killing one person and sending dozens to hospitals.

Cases such as this are far from rare.

More than half the waterborne disease outbreaks in the United States during the last half-century followed a period of extreme rainfall, scientists at Johns Hopkins University in Baltimore reported Tuesday.

They found that 51 percent of the outbreaks were preceded by a rainstorm ranking in the top 10 percent of storms for the area during that period. And 68 percent of the outbreaks followed storms ranked in the top 20 percent. The results were reported in the American Journal of Public Health.

While heavy rains and subsequent runoff have been assumed to be a factor in the transport of bacteria, the study is the first quantitative analysis of the relationship, the team said.

"We were quite struck by the strong relationship between rainfall and subsequent waterborne disease outbreaks," said Dr. Jonathan Patz, who led the research team.

Mary Fran Myers, co-director of the Natural Hazards Center at the University of Colorado, called the finding "research that's telling us something." She could recall no similar studies.

Patz said there are two messages: "One is that our current water facilities do need to be improved, and even today when we have heavy rainfall there is a public health risk."

Global warming concerns

"There are 950 communities still in the United States that have antiquated (sewer) systems, so that when you have heavy rainfall, the storm water, which is handled in the same system as sewage, you get overflows and you get contamination," he said in a telephone interview.

"The significance of the association between precipitation and disease is amplified when you consider the effects of global climate change, which predict an increase in precipitation in parts of the United States," added Patz, assistant professor of environmental health sciences.

The researchers at the Johns Hopkins Bloomberg School of Public Health studied 548 outbreaks of waterborne disease between 1948 and 1994 as reported by the Environmental Protection Agency and Centers for Disease Control and Prevention.

The most common type of outbreak was acute gastrointestinal disease.

The scientists compared the places and dates of the outbreaks with rainfall records for the nation's various watersheds collected by the National Climatic Data Center.

There were 133 disease outbreaks originating from surface water such as lakes and rivers, and the team found that they followed strong storms that occurred the month of the outbreak or the month before.

There was a longer lead time, up to three months, for outbreaks involving ground water such as wells or aquifers. Those sources accounted for 197 outbreaks.

In the remaining 218 outbreaks, it was not known if the water came from a ground or surface reservoir.

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