True, but, if I took every simple precaution I know of to prevent all of the unlikely but known conditions, I doubt I'd get anything done in a day. Or have much fun.
* Avoid cars.
* Wash hands after exposure to public transit and before touching one's face.
* Always wear sunscreen when exposed to the sun.
* Don't wear contact lenses.
* Wash hands after exposure to dust of any kind.
* Wear mask during moderately poor air condition (almost every day in SF Bay!)
* Don't swim in the south (killer amoebas)
* Don't breathe in the north-west (killer fungi)
* Don't walk in the north-east (insanity causing ticks).
* Drink out of only glass or stainless steel.
* Eat only fresh unprocessed foods.
* Never eat bacon or BBQ.
* Never drink alcohol.
* And definitely, never, ever, go to a hospital.