How many bacteria need to be present to cause foodborne illness?

The number of bacteria required to cause foodborne illness can vary significantly depending on the type of bacteria and the individual's health. For some pathogens, like Salmonella or E. coli, as few as 10 to 100 cells can be enough to cause illness in susceptible individuals. Other bacteria may require a larger quantity, such as thousands or millions of cells, to lead to infection. Factors such as the specific strain, food type, and the person's immune system also play a crucial role in determining the risk.