What is gastroenteritis? 

Gastroenteritis (tummy bug, food poisoning, traveller's diarrhoea, viral enteritis or intestinal flu) is a gut infection that causes stomach cramps, vomiting and diarrhoea. It is very common and is often caused by unclean food or water.

How did I get it? 

Your tummy upset may be due to:

• a virus passed on by someone who may or may not have symptoms
• bacteria from food that is not fresh or well-cooked, unclean water, hands, cooking or eating utensils. Bacteria can also be spread by flies. Meat, poultry, dairy products, eggs, shellfish and parboiled rice are the most commonly affected
• amoebas or parasites
• poisonous food such as toadstools. 

What happens? 

The infection irritates your stomach and gut making the muscles tighten, causing vomiting or diarrhoea. You can get sick from an hour to five days after getting infected, depending on the bug.

What will I feel? 

You may get cramps, have a gurgly, uncomfortable tummy, vomit and have watery diarrhoea which may be bloody or mucousy. You may also feel sick, shivery, have a headache and/or fever. It usually only lasts a few days, but may last longer.

If you become very weak, have trouble waking up, have sunken eyes, go very pale, stop passing water or get very dry skin and tongue, you may be dehydrated and need urgent attention.

How is gastroenteritis diagnosed? 

Mostly by the symptoms. If they are very bad or not settling, the doctor may send a stool (faeces) sample to the laboratory.

What makes it better?

• fluids; the most serious problems for people with a tummy bug, particularly those who are very young, very old or who have chronic health conditions, are dehydration and losing important minerals. Drink as much as you can, as often as you can (even if it is in little sips), especially after you have vomited or had diarrhoea. You can get rehydration salts and glucose solutions from your doctor or chemist. Or use watered-down, flat Coca-Cola, ginger ale or lemonade (not diet versions), weak cordial or suck on an iceblock. If vomiting and/or diarrhoea is very bad, or you have not held any fluids down for between 12 (older adults and small children) or 24 hours (healthy adults) then you should visit your doctor for a check-up
• rest
• a light, clear broth and bland food (plain bread, stewed apple, porridge, jelly, plain biscuits) when you feel ready to eat
• if your baby has a tummy bug, continue breast-feeding but give extra water. If they are bottle fed, give water on the first day, then watered down formula or milk from the second day
• children may not want to eat for a day or more. As long as they are drinking, don't worry.

What makes it worse? 

Drinking concentrated drinks (tea, coffee, full strength fruit juice), or eating milk products, fatty or fried food, raw vegetables, fruit or wholegrain breads too early in your recovery.

How can my doctor help me? 

Your doctor can give you rehydration salts if necessary, and maybe something to stop vomiting, cramps or diarrhoea (you could also talk to your pharmacist, as some of these products are able to be purchased at your local pharmacy). If you don't get better in five to seven days, are very weak, have other health problems or are very old or young, you may be put in hospital so fluids can be given by drip. Antibiotics are only used for bad infections.

How can I protect myself and others?

Handling food

• wash your hands before eating or preparing food and after going to the toilet
• if you work with food commercially, use latex gloves and avoid touching food with the hands where possible
• wash the tops of cans before opening
• wash all utensils, boards and surfaces used for meat, poultry, etc with hot, soapy water
• don't let raw food come in contact with these surfaces
• if it smells bad or looks dodgy throw the food out. 

Shopping

• buy perishable food only as you need it
• get it home from the supermarket and stored quickly
• check out use-by dates carefully
• don't leave poultry or meat in their store wrappers for more than two days. Rewrap in wax paper or plastic wrap
• when freezing, wrap tightly, date and use within six months. 

Cooking

• never defrost frozen foods on the bench: thaw in the fridge, in warm water or the microwave or cook them from frozen
• cook food thoroughly, particularly meat, chicken, eggs, milk products, fish and shellfish
• clean and cook chicken very well, pack stuffing loosely
• serve hot food hot (most bacteria are killed at 100°C) and cold food cold (bacteria stop growing at 0°C but can survive). They grow extremely well between 15°C and 51°C
• put leftovers in the fridge quickly and reheat well
• avoid raw fish, meats and shellfish unless you are sure they are well prepared and from a reliable place. 

Travelling/eating out

• look at how clean the eating establishment is
• be wary of food, even salad and cold cuts, that sit all day
• in developing countries: don't eat raw food, food from street stalls or peeled fruits; drink only bottled or boiled water or drinks; avoid ice
• use water purification tablets. 

Also see: Food and drink - safety tips for travellers

What happens if it is not treated? 

Most people get better in a few days. If they don't or if they are dehydrated, they may be put in hospital for more intensive treatment or to undergo further tests to determine what is causing the problem.

Written by Anna Mickell RCpN. Reviewed by everybody.