(HealthDay News) – Populations at risk, including older adults, pregnant women, and those with weakened immune systems, account for ≥90% of reported Listeria infections, according to research published in the June 4 early-release issue of the U.S. Centers for Disease Control and Prevention’s Morbidity & Mortality Weekly Report.

Benjamin J. Silk, PhD, from the CDC in Atlanta, and colleagues examined the illness rates and foods associated with Listeria outbreaks during 2009–2011, which were reported through three monitoring systems.

The researchers found that, from 2009–2011, >1,650 Listeria illnesses were reported to the CDC. About 20% of infections resulted in death, which occurred primarily among older people and as miscarriages or stillbirths. The most affected groups included older adults (aged ≥65 years); pregnant women, especially pregnant Hispanic women; and the immunocompromised. These populations accounted for 90% of reported Listeria infections. During the study period, 12 outbreaks resulted in 224 infections in 38 states, including a large outbreak in 2011 that was linked to whole cantaloupes from one farm. Six of the 10 outbreaks with an identified food source were linked to soft cheese (mainly Mexican-style), and two outbreaks were linked to raw produce (whole cantaloupe and pre-cut celery).

Listeria strikes hard at pregnant women, the elderly, and people with weakened immune systems, sending many to the hospital and causing miscarriage or death in as many as one in five,” Tom Frieden, MD, MPH, director of the CDC, said in a statement. “We need to develop new cutting edge molecular technologies to help us link illnesses and outbreaks to foods faster to prevent illness and death, which is why the President’s Budget proposes investing in new tools to advance this work.”

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