Diarrhoea is when you are passing stools more frequently than is normal for you or passing looser stools than usual. You can get diarrhoea as a result of stress or drinking too much caffeine or alcohol, but often it is caused by an infection in the bowel known as gastroenteritis. Gastroenteritis can be caused by a virus, bacteria or a parasite. It is very common for people travelling to other parts of the world, i.e. Asia, the Middle East, Africa and Latin America, to get bacterial or viral diarrhoea, also known as travellers’ diarrhoea. Normally, travellers’ diarrhoea will go away by itself within about 3 days.

If you have diarrhoea, you can dehydrate quite quickly, especially if you’re also vomiting, so you need to drink plenty of fluids to rehydrate.

Usually, severe travellers’ diarrhoea is caused by bacterial and viral infections. The season can affect the risk – you are more likely to pick up diarrhoea caused by bacteria in the rainy season (or diarrhoea caused by a virus in the dry season). The type of travel also influences this – camping and backpacking put you at a higher risk than business travel.

You also can pick up a viral infection by direct contact, so you need to wash your hands regularly to prevent it (especially after going to the bathroom, before you eat, after coming into contact with animals, or after contact with another person who has diarrhoea.) If you can’t wash your hands with soap and water, use a hand sanitiser.

You can also catch bacterial diarrhoea by eating contaminated food or drinking contaminated water. Bacterial diarrhoea is often severe and comes with cramps, headache, fever and loss of appetite, as well as nausea and vomiting. There are several things you can do to prevent getting it:
Drink bottled or sterilised water (use this for everything you might eat or drink, e.g. to wash fruit, clean your teeth or make ice). Don’t eat salads (the ingredients may have been washed in contaminated water).
Be careful if you eat dairy products, as they may be unpasteurised.

The chances of getting travellers’ diarrhoea may be minimised by taking special care of what you eat and drink. Wash your hands thoroughly before handling and eating food. Ensure all food is fresh, cooked thoroughly and served very hot (high temperatures kill most germs). Eat only foods prepared in a clean, reputable establishment – not from food stalls. Peel fruits and vegetables. Avoid salads, raw sea food, raw eggs (mayonnaise), unrefrigerated buffets, and food left standing at room temperature. Also avoid unpasteurised milk, ice, and ice cream from street vendors. Drink only bottled water (from sealed bottles), boiled water or water that has been filtered and disinfected; avoid local tap or drinking water.

Useful link: https://www.fitfortravel.nhs.uk/home