Water, cantaloupe blamed in Salmonella outbreaks

Mar 24, 2008 (CIDRAP News) – State and federal public health officials are managing two large Salmonella outbreaks, one linked to contaminated groundwater that has sickened as many as 216 people in Alamosa, Colo., and another that is apparently connected to imported Honduran cantaloupe and involves 59 illnesses in 16 states and Canada.

Salmonella in Colorado water
After state health officials confirmed dozens of Salmonella infections in Alamosa area residents, authorities tested the municipal water supply and found it was contaminated with bacteria, according to a Mar 21 emergency declaration from Colorado Gov. Bill Ritter.

Today the US Centers for Disease Control and Prevention (CDC) confirmed that the pathogen was Salmonella, according to a statement from David Svaldi, president of Adams State College in Alamosa. The town of about 8,700 people is in south-central Colorado in the San Luis Valley, an area known for growing cool-weather crops.

Media reports and official statements have not specified which Salmonella strain caused the illnesses.

Area residents have been under a bottled-water advisory since Mar 19, according to a statement from the Colorado Department of Public Health and Environment (CDPHE). According to an update on the Alamosa County Web site, authorities will begin a three-step process to clean up the municipal water system tomorrow. Residents have been advised that the bottled-water advisory may be in effect for up to 2 weeks.

The CDPHE confirmed the first Salmonella infection on Mar 14, according to Ritter's emergency declaration. As of yesterday, 216 cases of salmonellosis had been reported in Alamosa, of which 68 were confirmed by laboratory tests, according to the statement from Svaldi. Twelve Adams State students have reported symptoms, but laboratory tests have not yet confirmed the infections. Nine people have been hospitalized; no deaths have been reported.

Authorities have not said how they think the water became contaminated with Salmonella. Ken Carlson, an environmental engineering professor from Colorado State University, said Alamosa's water comes from five deep wells and is untreated, the Denver Post reported on Mar 21. More than half of the US drinking water supply consists of untreated groundwater, he told the Post, adding that groundwater typically never comes in contact with possibly contaminated surface water before reaching consumers.

"Generally that's been a good assumption. There have been very few outbreaks in these systems," Carlson told the Post.

Local residents are speculating that water could have been contaminated by sabotage or by an accident at a new water treatment plant that is under construction, according to the Post report.

Michael Beach, a waterborne diseases specialist with the CDC, said that in the past 20 years there have been only five reported instances of Salmonella contamination in municipal water, according to the Post. He said one case involved contaminated groundwater, two were linked to water-distribution system breaches, and two involved disinfection problems. Since 1971, none of the 15 recorded cases of Salmonella contamination in city water supplies were caused by sabotage, Carlson told the Post.

FDA, CDC investigate cantaloupe
Meanwhile, the US Food and Drug Administration (FDA) on Mar 22 warned consumers not to eat cantaloupe from Honduran grower Agropecuaria Montelibano and ordered FDA field offices to detain all of the company's cantaloupe shipments. The FDA said in a press release that between Jan 18 and Mar 5 it had received reports of 50 Salmonella cases in 16 states, along with 9 illnesses in Canada, linked through case-control studies to the consumption of Honduran cantaloupe.

According to a Mar 22 statement from the CDC, the patients were found to have the same genetic fingerprint of Salmonella Litchfield. Patients' ages range from under 1 year to 93 years. At least 14 patients have been hospitalized, but no deaths have been reported.

The FDA's traceback investigation indicated that cantaloupes consumed by patients with the outbreak strain were grown in Honduras, according to the CDC statement. Government statements did not make clear how the outbreak was linked to Agropecuaria Montelibano specifically. The FDA has advised US grocers, food service operators, and produce processors to remove the company's products from their stocks; however, the CDC said the products may still be in grocery stores or consumers' homes.

Consumers who have cantaloupes in their homes can check with the markets where they purchased the product to see if the fruit came from the implicated Honduran grower, the FDA said. The CDC said consumers who have the potentially contaminated cantaloupe in their homes should throw the product away.

See also:

Mar 24 statement from Adams State College President David Svaldi
http://www.adams.edu/news/mar0822/mar0822.php

Mar 22 FDA news release on cantaloupe contamination
http://www.fda.gov/bbs/topics/NEWS/2008/NEW01808.html

 

CDC statement on Salmonella outbreak linked to cantaloupe
http://www.cdc.gov/Salmonella/litchfield/

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