One of the things that is most confusing to people about sous vide cooking is why it is suddenly ok to cook chicken or pork at 140°F (60°C) when traditionally it has to be cooked to a much higher doneness.
The answer is we have always been taught that temperature is what makes food safe, but this is only half of the equation. What makes food safe is actually a combination of the temperature it is heated to and the length of time it is held at that temperature. That time and temperature combines to pasteurize the food, making it safe to eat.