Foodborne Illnesses / Listeria /

Who is Most at Risk of Becoming Ill with Listeria?

The elderly, pregnant women, and anyone immunocompromised is most at risk for contracting Listeria.

Several segments of the population are at increased risk and need to be informed so that proper precautions can be taken. The body’s defense against Listeria is called “cell-mediated immunity” because the success of defending against infection depends on our cells (as opposed to our antibodies), especially lymphocytes, otherwise known as “T-cells.” Therefore, individuals whose cell-mediated immunity is suppressed are more susceptible to the devastating effects of listeriosis, including HIV-infected individuals, who have been found to have a Listeria-related mortality of 29%.

Incidence of Listeria infection in HIV-positive individuals is higher than in the general population. One study found that:

The estimated incidence of listeriosis among HIV-infected patients in metropolitan Atlanta was 52 cases per 100,000 patients per year, and among patients with AIDS it was 115 cases per 100,000 patients per year, rates 65-145 times higher than those among the general population. HIV-associated cases occurred in adults who were 29-62 years of age and in postnatal infants who were 2 and 6 months of age.

Pregnant women naturally have a depressed cell-mediated immune system. While other systemic bacterial infections may result in adverse pregnancy outcomes at comparable frequencies, L. monocytogenes has particular notoriety because fetal complications largely occur in the absence of overt illness in the mother, delaying medical intervention. In addition, the immune systems of fetuses and newborns are very immature and are extremely susceptible to these types of infections.

Other adults, especially transplant recipients and lymphoma patients, are given necessary therapies with the specific intent of depressing T-cells, and these individuals become especially susceptible to Listeria as well.

According to the FDA, CDC, and other public health organizations, individuals at increased risk for being infected and becoming seriously ill with Listeria include the following groups:

  • Pregnant women: They are about 10-20 times more likely than other healthy adults to get listeriosis. About one-third of listeriosis cases happen during pregnancy. Fetuses are also highly susceptible to infection and severe complications.
  • Newborns: Newborns can develop life-threatening disease from perinatal and neonatal infections
  • Persons with weakened immune systems
  • Persons with cancer, diabetes, kidney, or gastrointestinal disease
  • Persons with HIV/AIDS: Individuals with HIV/AIDS are almost 300 times more likely to get listeriosis than people with healthy immune systems.
  • Persons who take glucocorticosteroid medications (such as cortisone)
  • Persons of advanced age: One risk assessment showed people over 60 years old were 2.6 times more likely to develop listeriosis than the general population. And in 2011, the median age of diagnosed cases in people who were not pregnant was 71 years old.