Cirque Meadows by Adam Johnson

Information on the 2011 Listeria Outbreak

photo of canteloupe

Please note that the Larimer County Health Department does NOT test for listeriosis. If you feel you should be tested for listeriosis, call your health care provider.

For questions and concerns about the cantaloupe/Listeria outbreak, please call CO-HELP at 1-877-462-2911. Operators are available to answer questions in English and Spanish.

What is the 2011 Listeria outbreak ?

In early September, the Colorado Department of Public Health and Environment noted an increase in reported cases of Listeria infections in Colorado. Investigation revealed that the source was most likely cantaloupe grown in eastern Colorado on Jensen Farms.

As of October 6, 2011, a total of 109 persons infected with Listeria monocytogenes have been reported from 24 states, and 21 of them have died. All illnesses started on or after July 31, 2011.

Note: the incubation period for listeriosis infection can be anywhere from 2 - 70 days. Therefore, as of early October, some infected individuals still may not be showing symptoms.

32 of the infected are from Colorado, and 5 of those have died.

What is listeriosis?

Listeriosis is an infection usually caused by eating food contaminated with the bacterium Listeria monocytogenes. It is believed that the outbreak in September, 2011, is caused by cantaloupe from Jensen Farms.

The disease primarily affects older adults, pregnant women, newborns, and adults with weakened immune systems. However, rarely, persons without these risk factors can also be affected. The risk may be reduced by following recommendations for safe food preparation, consumption, and storage.

What are the Symptoms of listeriosis?

Though it is a foodborne illness, symptoms are not just gastrointestinal. The Listeria bacteria spread and infect beyond the GI system.

For most people, symptoms include:

  • fever and muscle aches (most often)
  • diarrhea or other gastrointestinal symptoms,
  • headache
  • stiff neck
  • confusion
  • loss of balance
  • convulsions

Symptoms in pregnant women:

Pregnant women typically experience only a mild, flu-like illness. However, infections during pregnancy can lead to miscarriage, stillbirth, premature delivery, or life-threatening infection of the newborn.

What is the incubation period of the bacteria?

The incubation period, from the time of eating the infected food to the onset of illness can range from 2 - 70 days.

How do you prevent it?

Wash ALL raw fruits and vegetables thoroughly before slicing or eating. Scrub food that has bumpy skins, e.g. cantaloupes or avocadoes, with a brush and rinse well after scrubbing. For fruits and vegetables whose skin/rind is not eaten, using soap will clean the outside better before you cut into it.

  • Avoid raw milk and foods made from raw milk.
  • Cook meats, poultry and seafood well.
  • Cook leftover foods until hot.
  • Wash your hands, knives and cutting boards after handling uncooked foods.
  • During pregnancy, do not eat soft Mexican-style cheeses. Also avoid feta, Brie, Camembert and blue-veined cheeses. Instead, eat hard cheeses, processed cheese and yogurt. Avoid cold cuts such as bologna, hot dogs and pate unless you cook them well.

Can listeriosis be treated?

Yes, listeriosis can be treated with antibiotics. When infection occurs during pregnancy, antibiotics given promptly to the pregnant woman can often prevent infection of the fetus or infant.

When should I call my doctor?

If you are pregnant or immune compromised and are confident you have eaten a Jensen Farms cantaloupe in the past 2 - 70 days, call your health care provider to let them know and immediately upon experiencing any symptoms of listeriosis.

If you are generally healthy and confident that you have eaten cantaloupe from Jensen Farms sometime over the past 2 - 70 days, call your physician upon developing any of the symptoms.

For More Information

For questions and concerns about the cantaloupe/Listeria outbreak, please call CO-HELP at 1-877-462-2911. Operators are available to answer questions in English and Spanish.

For general information on Listeria, listeriosis and updates on the current outbreak, visit:

For information on food safety and foodborne illness, visit:

Background Image: Cirque Meadows by Adam Johnson. All rights reserved.