How long must water boil to be sterilized, according to the CDC?

If you don’t have safe bottled water, you should boil your water to make it safe to drink. Boiling is the surest method to kill disease-causing germs, including viruses, bacteria, and parasites. You can improve the flat taste of boiled water by pouring it from one container to another and then allowing it to stand for a few hours, or adding a pinch of salt for each quart or liter of boiled water. Steps for boiling water: bring the clear water to a rolling boil for 1 minute (at elevations above 6,500 feet, boil for 3 minutes). Let the boiled water cool. Store the boiled water in clean sanitized containers with tight covers.

Source: CDC