Never drink tap water. Bottled water is generally safe – check that the seal is intact at purchase. Avoid ice unless you know it has been made without tap water. Be careful of fresh juices served at street stalls in particular – they're likely to have been watered down with tap water or may be served in jugs/glasses that have been rinsed in tap water. Avoid fruit that you don't peel yourself, as it will likely have been rinsed in tap water. Alternatively, rinse fruit yourself in mineral water before you eat it. Boiling water is usually the most efficient method of purifying it. The best chemical purifier is iodine. It should not be used by pregnant women or those with thyroid problems. Water filters should also filter out most viruses. Ensure your filter has a chemical barrier such as iodine and a small pore size (less than four microns). In tourist areas, some guesthouses, cafes and restaurants use water filters; use your own judgment as to whether you think this water will be safe to drink.