Tips to keep you healthy:
1 - Have your food cooked thoroughly. This is equal to refusing to eat any raw or half-cooked food, especially street food.
2 - Drink only bottled water or chilled boiled water. Tap water is not drinkable in Vietnam so your water bottle will not be of much use here. You can buy a 1.5l mineral water and carry with you around. Try to avoid ice at all times.
3 - Wash hands frequently, before eating and after using the toilettes. It might be best to keep a hand-sanitizer handy and use it often as you can. Hand-sanitizer is also available for purchase at most supermarkets in Vienam.
4 - Avoid lettuce, unpeeled fruits and vegetables in street vendors. Local authorities also advise that you thoroughly wash fruits carefully before consuming.
5 - Stay active. Travelling to an exotic country may sometimes mean overstuffing yourself with seafood and foreign cuisines. Help your digestive system by walking lightly after a heavy meals and stay active during the day with mildly rigorous activities such as hiking, trekking and swimming.