Listeria outbreak mystery

Oct 14, 2011

Listeria, a mysterious bacteria occasionally found to contaminate foods, has received more than its share of news recently. Especially deadly for vulnerable consumers such as the elderly and pregnant women, listeria is very hard to trace because it can take as long as two months before its victims become ill.

The recent listeria outbreak from cantaloupes is now the deadliest foodborne illness outbreak in the U.S. in more than 25 years.

According to federal officials, this is not the first time cantaloupe has been the carrier of this bacteria. It has a record of at least 19 previous outbreaks, and over 1,000 illnesses since 1984.

Still under investigation, Jensen Farms in Granada, CO, is the producer tied to the recent outbreak.

According to the Centers for Disease Control (CDC), 23 people have died from the recent outbreak while another 116 have been sickened. Not since 1985, when listeria from Mexican-style soft cheeses killed 52 people, has a foodborne illness outbreak been this deadly in America. The current death toll also surpassed a 1998 listeria outbreak linked to processed meats that killed 21 people.

Deaths have been reported in Colorado, Indiana, Kansas, Maryland, Missouri, Nebraska, New Mexico, New York, Oklahoma, Texas, Louisiana and Wyoming. Colorado has the most illnesses with 34, while Texas has reported 17.

Food and Drug Administration (FDA) investigators said Colorado health officials found listeria in cantaloupes grown at Jensen Farms, in grocery stores, and from a victim’s home. Matching disease strains were also found on equipment and cantaloupe samples at Jensen Farms’ packing facility in Granada, CO. FDA officials have said they were looking at the farm’s water supply and possible animal intrusions, among other things, to figure out the source of the problem.

Jensen farms shipped the cantaloupes to about half the states, but said that they were not sure where all of the cantaloupes went because they often get resold.

Some companies may be unaware that they bought or distributed tainted cantaloupe.

CDC said the median age of those sickened is 78, and most people who are ill are over 60.

Both industry and federal officials argue frequently that the current incident is “unprecedented,” that previous outbreaks linked to cantaloupes have typically involved salmonella or a norovirus. “This is the first outbreak that we’ve seen with listeria and that is a surprise and certainly something that we need to be mindful of,” FDA’s Dr. Margaret A. Hamburg said.

Still other officials continue to point out the difficulty of finding contaminants on melons. For example, Trevor Suslow, an extension specialist at the University of California, Davis, who has done industryfinanced research into food safety and cantaloupes, said that the fruit’s rough skin made it more susceptible to harboring unwanted bacteria. “[L]ots of areas for microbes to get in and attach and hide,” Suslow said.

He noted that, “It is best to keep cantaloupes dry to reduce the possibility that bacteria will grow on them.” In California, growers typically do not immerse melons in water to wash them and use chilled air to cool them. In other regions, he said, cantaloupes are often washed with a water spray and are cooled with sprays of cold water as well. Those techniques may be more likely to spread bacteria.

Stephen Patricio, a melon shipper who is the chairman of the California Cantaloupe Advisory Board, a trade group, said sales were plummeting, even though only melons from the farm in Colorado were implicated. He noted that California growers had repeatedly been hurt by outbreaks that were a result of lax practices elsewhere—and now, that is happening again. — Traci Eatherton, WLJ Editor