THURSDAY, Sept. 5 (HealthDay News) -- Of all the dangerous
bacteria lurking in foods, perhaps the most deadly is listeria, and
the lesson from a 2011 outbreak is to always handle food safely,
U.S. health officials say.
In the summer and fall of 2011, cantaloupes contaminated with
listeria sickened 147 people in 28 states, killing 33 of them. That
listeria outbreak -- the deadliest in a decade -- was unusual
because listeria is rarely associated with fresh produce, according
to a new report from the U.S. Centers for Disease Control and
Although rare, listeria is an important public-health issue
because of its severity, said report co-author Benjamin Silk, a CDC
epidemiologist in the division of foodborne, waterborne and
environmental diseases. "Nearly all people who have listeria
infections diagnosed are hospitalized, and about one in five die,"
The new report, published Sept. 5 in the
New England Journal of Medicine, highlights lessons learned
from an investigation into the 2011 outbreak.
The authors found that for the 145 people for whom complete
records were available, all but two were hospitalized and nearly
Most of those sickened were in their 60s or older and suffered
from other illnesses. But there also were seven
pregnancy-associated infections among four women and three infants.
One of the four women miscarried because of the infection.
Overall, this is typical of the general consequences of a
listeria outbreak, one expert said.
"Listeria is only a problem for immuno-compromised folks and pregnant women, but in those cases people can and do get quite ill and almost all are hospitalized," said Dr. Marc Siegel, an associate professor of medicine at the NYU Langone Medical Center in New York City.
"In this case, pregnant women were a small percentage, though they are usually more," he said. "Outbreaks are limited as healthy people don't generally get ill."
The contaminated cantaloupes were traced to a Colorado grower,
and while the exact cause of the contamination isn't known,
unsanitary conditions were likely the culprit, according to the
"The problem is that listeria bacteria grows on produce -- in this case cantaloupes -- and occurs especially when proper precautions aren't taken at the farm or processing facility," Siegel said.
One possible contributor to the outbreak is inadequate facility
and equipment design, which hampered thorough cleaning of surfaces
the melons could touch, according to the report. Another possible
route to contamination is a truck kept next to the processing line
that went to and from a cattle operation.
In addition, the Colorado farm did not cool its cantaloupes
before placing them in cold storage, which may have caused
condensation that promoted the growth of listeria.
"This outbreak confirms the viability of raw produce, including cantaloupe, as a vehicle for listeriosis and highlights the importance of preventing produce contamination within farm and processing environments," the report noted.
Listeria is associated with about 1,600 infections in the United
States annually, Silk said. A partnership between the CDC and state
health departments, known as the Listeria Initiative, enabled the
agency quickly to identify the source of the 2011 outbreak, he
The CDC continues to monitor and follow up on all listeria
cases, Silk said. In addition, the FDA has stepped up inspections
of cantaloupe farms and has issued guidelines to cantaloupe
The best way to avoid listeria is to follow common-sense
food-safety procedures, Silk said.
To help prevent infection, the CDC recommends you do the
For more information on listeria, visit the
for Disease Control and Prevention.
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