A month-old outbreak of listeriosis in 18 states is now officially the most deadly outbreak of foodborne illness since poison peanut butter killed nine people with Salmonella Typhimurium in late 2008 and early 2009.

The federal Centers for Disease Control and Prevention (CDC) in Atlanta late Tuesday reported that the Listeria outbreak caused by contaminated whole cantaloupes has resulted in at least 13 deaths among 72 illnesses.

In terms of fatalities, this outbreak is one of the worst in the U.S. related to foodborne illnesses. A Listeria outbreak in 1985 linked to Mexican-style fresh cheese killed 29. In 1998 there were 14 listeriosis deaths linked to deli meats.

Cantaloupes have been responsible for at least 36 foodborne illness outbreaks since 1990, although this is the first one involving Listeria.  

In its update on the current outbreak investigation, the CDC said four people have died in New Mexico, two in Colorado, two in Texas and one each in Kansas, Maryland, Missouri, Nebraska and Oklahoma after eating tainted cantaloupe.    

Local media reports have attributed a second death in Kansas and another in Wyoming to the Listeria outbreak, but those were not included in CDC figures through 11 a.m. EDT, Sept. 26.

The CDC report translates into a fatality rate of 18 percent. Based on past Listeria outbreaks, it will likely go higher. A Canadian Listeria outbreak in 2008 had a fatality rate of 40 percent.

Fifteen illnesses have been reported in Colorado, 14 in Texas, 10 in New Mexico, eight in Oklahoma, six in Nebraska, five in Kansas and two each  in Wisconsin and Indiana, with single cases in California, Florida, Illinois, Maryland, Missouri, Montana, North Dakota, Virginia, West Virginia and Wyoming, according to the CDC.

The CDC says the first reports of illnesses in the outbreak were on July 31. Those sickened have ranged in age from 35 to 96. At least 66 were hospitalized. Most of the patients are over 60 or have health conditions that weaken their immune systems.

Listeriosis can be a severe illness for the elderly or people with underlying health problems. It can also cause pregnant women to miscarry.

The cantaloupes were removed from the market Sept. 14 by Colorado’s Jensen Farms, which  marketed the melons under the Rocky Ford brand and had shipped from July 29 to Sept. 10. Listeria contamination was found both on Jensen’s melons and its processing equipment.

A Denver television station is reporting that state and federal investigators are interested in a biosolids firm operating near Jensen Farms. Parker Ag Services, according to Denver’s 7News sprays human waste from New York on Colorado fields, including one across from Jensen Farms.

The station quoted University of Georgia food safety expert Michael Doyle as saying it is possible for treated human waste to dry into dust and become airborne.

Jensen Farms says it does not use biosolids.

CDC Outbreak Map: