Eating on the street without getting ill

The US Centers for Disease Control and Prevention says food and drink from street vendors carry a higher risk of illness, and that fully cooked food served hot is among the safest choices. It advises avoiding salads and uncooked vegetables where water may be unsafe, avoiding ice unless you are reasonably sure it was made with safe water, drinking bottled water from an unopened factory-sealed container, and eating fruit you have washed in safe water and peeled yourself. Water that has just been boiled, as in tea or coffee, is generally safe.

On hands, the same advice is to wash with soap and water before eating, or to use a sanitiser with at least 60% alcohol when soap is not available. Sanitiser works less well on greasy hands and against norovirus.

The scale of the problem is global, not Vietnamese: the World Health Organization estimates that about 866 million people fall ill each year from contaminated food, roughly one in nine people worldwide.

The UK Foreign Office reports deaths and serious illness in Vietnam from alcoholic drinks containing methanol, including drinks bought in licensed bars, shops and hotels in tourist areas. Even small amounts of methanol can kill, and it cannot be detected by taste or smell. The same advice says to avoid buying liquor from street vendors or strangers, and to get urgent medical help if anyone shows symptoms after drinking.

For street eating, that means being cautious with unlabelled rice spirit, home-made fruit wines and cheap cocktails. Bottled beer and sealed soft drinks are the lower-risk choice. The Foreign Office also advises buying your own drinks and keeping them in sight, and being wary of snacks or drinks offered by new acquaintances.

Mild traveller's diarrhoea usually settles within a few days. Drink plenty of safe fluids, use oral rehydration salts if you have them, and eat plain food such as rice porridge (chao) or plain rice until you feel better. Pharmacies are common in Vietnamese cities.

Get medical help if you have a high fever, blood in your stool, severe pain, signs of dehydration such as dizziness or very little urine, or if symptoms do not ease after a couple of days. Children, older travellers and anyone who is pregnant or has a long-term condition should seek help sooner. The UK Foreign Office advises travel insurance that covers medical treatment and evacuation, and to contact the insurer quickly if you are referred to a hospital. For an ambulance, dial 115.