Listeria Outbreak Now 2nd Largest in U.S. History

21 Deaths, 1 Miscarriage as Toll From Listeria Linked to Cantaloupes Rises

By Daniel J. DeNoon
WebMD Health News

Reviewed by Laura J. Martin, MD

Oct. 10, 2011 -- The current listeria outbreak from cantaloupes is now the second largest in U.S. history.

The toll now stands at 109 cases and 21 deaths. A pregnant Iowa woman miscarried due to cantaloupe-linked listeria infection.

A person infected with listeria may take up to two months to develop the serious illness known as listeriosis. It may be several weeks before an illness is reported to the CDC, so cases that began after Sept. 11 may not yet be counted.

That count now has passed the 1998 listeria outbreak in hot dogs and deli meats. That outbreak sickened 108 people. There were 14 deaths and four miscarriages.

The largest U.S. listeria outbreak was in 1985, when 142 people became ill after eating Mexican-style cheese contaminated with unpasteurized milk. Pregnant women were disproportionately affected. There were 18 adult deaths, 20 miscarriages/stillbirths, and 10 deaths of newborns.

Pregnant women are at high risk of listeriosis. While the woman herself usually gets only flu-like symptoms, listeria bacteria tend to infect the placenta. Infection of the fetus often causes miscarriage or stillbirth. Infection of the newborn during birth can result in death or permanent disability.

Also at risk are people over age 60, people with diabetes or diseases that weaken immunity, and people taking immunity-suppressing drugs.

The current outbreak of listeria from cantaloupes isn't over, even though it's very unlikely that any of the contaminated cantaloupes are still in refrigerators or on grocery shelves. Melons from Jensen Farms' Granada, Colo., packing plant were last shipped on Sept. 10. Cantaloupes have only about a two-week shelf life.

Listeriosis Symptoms

Although listeriosis is a food-borne illness, when symptoms appear it usually means the bacteria have escaped the digestive tract and are spreading throughout the body. Listeriosis sometimes results in fatal meningitis or encephalitis.

Listeriosis usually begins with diarrhea or other intestinal symptoms. Patients soon develop fever and muscle aches. What happens next depends on a person's risk factors:

  • While pregnant women usually get a mild flu-like illness, listeria infection can cause miscarriage, stillbirth, premature delivery, or fatal infection of the newborn.
  • Other adults may develop headache, stiff neck, mental confusion, loss of balance, and convulsions.
  • Symptoms may occur as soon as soon as three days or as long as two months after infection. The usual incubation period is thought to be one to three weeks.

Foods typically linked to listeriosis are deli meats, hot dogs, and soft cheeses made with unpasteurized milk. Produce is less often linked to outbreaks, although listeria occurs in soil and water. Listeria bacteria are killed by cooking, but they can grow and multiply in refrigerators.

In refrigerators where listeria-contaminated foods have been stored, other foods often become contaminated. So does the refrigerator itself, which should be thoroughly cleaned with soap and water and then wiped down with a solution of diluted bleach.

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SOURCES: CDC web site.FDA web site.Iowa Department of Health web site.Mead, P.S. Epidemiology and Infection, August 2006.Linnan, M.J. The New England Journal of Medicine, Sept. 29, 1988.

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