Listeriosis, more commonly known as listeria, is a rare but potentially deadly bacterial infection with a wide variety of possible symptoms ranging from damage to the central nervous system to nausea and diarrhoea. The disease can infect humans, farm animals, and wild animals, with weaker individuals such as newborns, pregnant women, the elderly, and those with immune system deficits such as humans who are HIV positive being particularly at risk.
Listeriosis is caused by the Listeria monocytogenes gram-positive bacterium. Its typical path into the body is through ingesting contaminated food. This can include raw meat and seafood but it is dairy products that seem to be the most likely sources. This is particularly true in the case of soft cheeses and unpasteurized milk and pate. Four different syndromes have been identified including infection in pregnancy, infection of the neonate, infection of the central nervous system, and gastroenteritis.
In pregnancy the listeria proliferate in the vagina and uterus causing fever, pain, and headache, but perhaps even causing the death or premature birth of the infant. There are early and late onset versions of neonatal infection. The early-onset variety may bring on premature birth. The late-onset variety, meanwhile, could cause meningitis. The third form of the infection, to the central nervous system, can lead to a variety of problems such as encephalitis, meningitis, and seizures. The fourth route for the disease, causing gastroenteritis, can lead to problems such as diarrhoea, nausea, and convulsions.
Incidences of infection by listeria are very low. In the US, for example, the rate is under 3 infections per year per million people. In Sweden the rate is around 5 per year per million people. Of these cases around 30% are in pregnant women and around 70% of the remainder are to be found in individuals with compromised immune systems such as HIV/AIDS patients.
Mortality rate from listeria is around 20-30%. Different problems caused by the bacteria take different lengths of time to treat. Meningitis takes around 3 weeks, for example. Treatment is usually with an antibiotic called ampicillin. This may be used in conjunction with a second, potentially complementary, antibiotic called gentamicin. But of course prevention is better than cure. This can be achieved with the correct handling, cooking, and eating of the potentially harmful foods, including re-heating foods thoroughly, and through educating high risk groups on the dangers, letting them know which foods they would be better off avoiding.