Meet Sal. You've met before, maybe at a restaurant, but you might not have been properly introduced: Salmonella's the name (pronounce it with the 'l', even though its namesake is its discovering pathologist Daniel Elmer Salmon), and contaminating the food you eat is the game.
We associate this incompetent, rod-shaped microbe, a close cousin to our friend Escherichia, or e. coli, with undercooked chicken and raw eggs, for the most part, but that's only a small part of the story. Salmonella is a genus of zoonotic bacteria (meaning various strains of it can be transmitted from animals to humans and / or vice versa) of which there are thousands of different species. Many species of salmonella are not harmful to humans at all, though they may be dangerous to animals; the reverse is also true. According to the Surveillance Report from the Food Diseases Active Surveillance (FoodNet) for 2007, salmonella is the most-reported type of bacterial infection.
Although one strain is responsible for typhoid fever, we're most familiar with salmonellosis, or food-poisoning. According to the CDC, there are 1.4 million cases of salmonellosis each year, with around 400 deaths.
Unlike many other bacteria, sneaky Sal does not usually affect the taste of the food it's contaminated. This comes in handy for it, since it takes a high concentration, usually in a significant amount of food, to cause sickness in a healthy adult. In the cases of those with weak or compromised immune systems, however, such as HIV or transplant patients, and especially with pregnant women, infants and very small children, that's not always the case. In fact, with infants, even breathing contaminated dust can be enough.
In most people the symptoms, which usually manifest 48 – 72 hours after ingestion, are very mild – diarrhea, vomiting, cramps and fever. Headache and chills are also common. The symptoms can last a few days, and in some cases can be managed without medical care, though that's never advisable. In children it can, very often, infect outside the intestine, causing Salmonella meningitis, and in a very small number of cases salmonellitis can lead to Reiter's syndrome – a condition involving sore joints, eye irritation and painful urination – which can last several months and lead lead to a particularly hard-to-treat form of chronic arthritis.
Since this zoonotic microbe makes its home in the digestive tract, people contract it by consuming food that has come into contact with animal feces. In the case of chickens, this obviously means eggs as well as meat. It's also strongly associated with reptiles, so it's best to wash your hands after handling your pet iguana – and maybe save kissing it on the lips for special occasions. However, it's very long-lived and hardy; living microbes have been found in hardened, 2–year-old animal scat. It's very easy to cross-contaminate the meal you're preparing simply by cutting your salad vegetables on the same cutting board you used to slice your meat, or by using a wooden board rather than a plastic one for meat-preparation.
It goes to follow, then, that surfaces like your kitchen tiles and the grout between them might also be welcoming, friendly resort destinations. Frequent cleaning and regular visits by a professional carpet-and-tile cleaner can keep the number of toxic tourists in your home to a minimum.