Salmonella, fears over which sparked a cautionary recall of Kinder chocolate eggs in several European countries on Tuesday, is one of the most common causes of food-borne outbreaks.
Named after the American veterinarian who helped discover the bacteria, Daniel Elmer Salmon, salmonella often causes mild illness, but can be life-threatening in extreme cases.
It is most often transmitted to humans who eat food contaminated with the faeces of an infected animal, according to the US Centers for Disease Control (CDC).
This often happens when people consume raw or undercooked food like meat and eggs, or when people handling food fail to wash their hands.
Less often, unwashed fruits and vegetables can become infected. Whether or not a person contracts salmonellosis, the infection caused by salmonella, depends on the type of bacteria and the quantity consumed.
While an estimated 94 percent of salmonellosis is transmitted by food, contact with chicks and pet turtles can be a source of infection, the CDC said.
If contaminated foods are distributed widely across borders, it can infected vast numbers of people.
Around 224,000 people were made sick by infected ice cream in the United States in 1994.
A decade earlier in France, at least 25,000 were infected by a food source that was never identified, according to the Pasteur Institute.
Symptoms usually show up around three days after infection and often include diarrhoea, vomiting, fever and stomach cramps.
A healthy adult normally recovers within a few days but in some cases, an infection can be dangerous or even fatal.