People with certain conditions, including leukemia, other cancers and pregnancy, are at the greatest risk of getting sick from the foodborne bacterium Listeria, French researchers report in a new study.

Doctors and public health officials have known that these conditions make people more vulnerable to listeriosis, but this study is the first to rank the size of the risk for people with each condition.

The results "will help focus risk communication for the medical community," said Ramon Guevara, an epidemiologist for the County of Los Angeles Department of Public Health, who was not involved in the study.

The study looked at nearly 2,000 cases of listeriosis in France — affecting 39 out of every 10 million people — from 2001 to 2008.

Despite its rarity, listeriosis is still considered an important public health concern because it’s relatively deadly compared to other food-borne illnesses, lead author Dr. Véronique Goulet at the Institut de Veille Sanitaire in Saint-Maurice wrote in an email to Reuters Health.

More than 400 of the 2,000 people who developed listeriosis died.

None of the cases involved an outbreak.

About one in six of the listeriosis cases in France affected pregnant women.

Incidence of Listeriosis and related mortality among groups at risk of acquiring Listeriosis
23.dec.11
Clinical Infectious Diseases
Véronique Goulet, Marjolaine Hebert, Craig Hedberg, Edith Laurent, Véronique Vaillant, Henriette De Valk, and Jean-Claude Desenclos
http://cid.oxfordjournals.org/content/early/2011/12/12/cid.cir902
Abstract
Background. Listeriosis is a foodborne disease of significant public health concern that primarily affects persons with recognized underlying conditions or diseases that impair cell-mediated immunity. The degree of risk posed by the different underlying conditions is crucial to prioritize prevention programs that target the highest risk populations.

Methods. We reviewed cases of listeriosis reported in France from 2001 to 2008. Numbers of cases and deaths were tabulated by age and underlying condition. Measures of the impact of specific underlying conditions on the occurrence of listeriosis were calculated. For estimating the total number of persons living with specific diseases, we applied prevalence estimates of these diseases to the French population. Underlying conditions were ranked by the degree to which they increased the risk of listeriosis.

Results. From 2001 to 2008, 1959 cases of listeriosis were reported in France (mean annual incidence 0.39 per 100 000 residents). Compared with persons <65 years with no underlying conditions, those with chronic lymphocytic leukemia had a >1000-fold increased risk of acquiring listeriosis, and those with liver cancer; myeoloproliferative disorder; multiple myeloma; acute leukemia; giant cell arteritis; dialysis; esophageal, stomach, pancreas, lung, and brain cancer; cirrhosis; organ transplantation; and pregnancy had a 100–1000-fold increased risk of listeriosis.

Conclusions. To be effective and acceptable to physicians and patients, listeriosis prevention strategies should be targeted based on evidence of increased risk. Stringent dietary guidance, to avoid specific foods with a high risk for Listeria contamination, should be targeted to pregnant women and to others at highest risk of listeriosis.