Gastroenteritis | Pokenga whēkau

Gastroenteritis or gastro in adults

Key points about gastroenteritis

  • Gastroenteritis (pokenga whēkau) is a gut infection that causes diarrhoea. It can also cause fever, stomach cramps and vomiting. 
  • The word gastroenteritis or gastro covers tummy bugs, food poisoning, traveller's diarrhoea, viral enteritis and intestinal flu.
  • It can be caused by viruses which pass from person to person, sometimes via surfaces or food.
  • It can also be caused by drinking water or food that's been contaminated by toxins or bacteria (food poisoning) or by parasites.
  • It's important to stay hydrated by drinking plenty of fluid, especially as an older adult or a child.
  • Wash your hands carefully with soap to stop the spread.
Young man tramping holds stomach in pain
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Gastroenteritis (pokenga whēkau/gastro) is a gut infection that causes diarrhoea lasting from a few days up to a month.

Gastroenteritis is very common in Aotearoa New Zealand and is often caused by contact with an infected person or unclean food or water.

Your stomach upset may be due to:

  • a virus passed on by someone who may or may not have symptoms
  • bacteria from food that's not fresh or is undercooked, or unclean water, hands, cooking or eating utensils
  • amoebas or parasites from food or water
  • toxins from bacteria or viruses.

Common foods that could be contaminated are meat, poultry, dairy products, eggs, shellfish and parboiled rice.

Raw chicken and vegetable on the same board is a risk for gastroenteritis

Image credit: Canva

Examples of infections that cause gastro

The infection irritates your stomach and gut, making the muscles tighten and causing diarrhoea and sometimes vomiting. Symptoms can begin an hour or up to 5 days after you've been infected depending on the type of infection. 

Symptoms include:

  • diarrhoea (runny poo which can be watery, bloody or mucous)
  • stomach cramps
  • feeling sick and weak
  • lethargy
  • loss of appetite
  • headache
  • fever (high temperature).

These symptoms usually only last a few days, but may last up to a few months depending on the cause.

Make an appointment to see your healthcare provider:

  • if your faeces (poo) contains blood or pus
  • if you have long-term health problems which weaken your immune system
  • if your diarrhoea has lasted for longer than a week.


See your healthcare provider immediately if you:

  • become very weak
  • feel drowsy
  • have sunken eyes
  • don't pass urine for 8 hours or more
  • get very dry skin or a dry tongue.

You could be dehydrated and require rehydration immediately. Read more about dehydration.

Diagnosis

Diagnosis is mostly based on your symptoms. If they are very bad or not settling, your healthcare provider may send a stool (faeces/poo) sample to the laboratory to identify the type of infection.


Treatment

Most people recover without needing any medicine. The best thing to do when you have gastroenteritis is to rest and keep drinking small amount of fluids to prevent dehydration. Older adults and children are most at risk of dehydration.

Norovirus infections are the most common cause of gastroenteritis and antibiotics don't work for them. For most types of food poisoning antibiotics don’t make you better any faster. There are medicines to stop diarrhoea or vomiting. However, it is important to see your healthcare provider before you use these medicines as they can have side effects which are worse than the illness itself, or make your illness last longer.

See our topic on diarrhoea for self-help and treatment options for diarrhoea and/or vomiting. It includes information on children and dehydration, and when to contact your healthcare provider.

Gastroenteritis isn't usually serious and most people recover without seeing a healthcare provider. However, some people may need to seek help and get treated in a hospital if they get dehydrated, particularly:

  • older adults
  • children less than 6 months of age.

Read more about gastroenteritis in children and dehydration.

Here are some things you can do when you have gastroenteritis:

  • Get plenty of rest.
  • Drink small amount of fluids often. Aim for 1 to 2 sips every few minutes. Slow down if feel like you might be sick. A good goal is to drink 2 litres in a day.
  • Drink water or watered down juice (1 part juice to 5 parts water).
  • Avoid tea, coffee and alcohol.
  • Avoid fatty, oily or sugary food and drinks. This includes sports drinks as they can make diarrhoea and tummy cramps worse.
  • Use oral rehydration salts if you have diarrhoea for more than a few days and you're not eating, or if you have both vomiting and diarrhoea. Oral rehydration salts are available at local pharmacies without prescription.

Apps reviewed by Healthify

You may find it useful to look at some Digestive health apps and Nutrition, exercise and weight management apps.

Careful handwashing is the most important way to prevent the spread of gastroenteritis. If you don't have access to soap, use hand sanitiser. Don't go to school, day care or your workplace until you've had no diarrhoea for 48 hours.

The following advice on food preparation, cooking and storage while you're at home comes from the Ministry of Primary Industries.


Preparing food

  • Wash your hands with soap and dry them well before handling, cooking, and eating food.
  • Wash chopping boards and kitchen tools in hot, soapy water and dry them well after using with raw meat or seafood.
  • Use different chopping boards for raw meat, seafood, and ready-to-eat foods like salads and cheese.
  • Don't wash chicken or raw meat. Washing will spread bacteria in your kitchen and may contaminate other food.
  • Wash your hands after handling eggs.
  • Keep surfaces and kitchen utensils clean and dry before and after handling eggs.
  • Use clean eggs free from dirt, faecal matter (poo), and cracks.


Cooking food

  • Make sure poultry, pork, processed and minced meat is cooked right through to kill harmful bacteria. Chicken and sausage juices should run clear and the meat shouldn't be pink in the middle.
  • Use a meat thermometer to check temperatures at the middle of the thickest part (where the temperature should be 75°C or more).
  • Defrost frozen foods thoroughly so they cook properly in the middle. Or, follow cooking instructions on labels or packaging that say you can cook the food directly from frozen.
  • Use 1 set of utensils for raw meat and chicken, and another set for cooked food. Put cooked items on a clean plate, not on the one that's been used for raw ingredients.
  • Check the use-by dates on food packaging. Don't buy, eat or drink once this date has passed.
  • If food is labelled with a best-before date, it's all right to eat the food after the date has passed, as long as the food is not showing signs that it's gone 'off'. Use your sense of smell, and look for signs of decay or mould. If in doubt, chuck it out.


Storing food

  • Refrigerate or freeze any leftovers within 2 hours – no food should be left at room temperature longer than that. 
  • Keep eggs in the fridge after purchase.
  • Cool hot foods for up to 30 minutes in room temperature before refrigerating to prevent raising the temperature in the fridge.
  • Cool large portions of hot food by dividing into smaller containers (this helps the food to cool faster), then cover, and refrigerate.
  • When eating outdoors, keep chilled foods (like salads) in a chilly bag or bin with ice packs until needed.
  • Eat leftovers within 2 days.
  • When in doubt, chuck it out.


Storing food in your fridge

Most harmful bacteria can't grow at low refrigeration temperatures. Set your fridge temperature between 2°C and 5°C and follow these tips.

  • Keep raw and cooked foods separate in the fridge.
  • Refrigerate raw meat on the bottom shelf, and keep it separate from cooked or other ready-to-eat foods.
  • Keep cooked food on a higher shelf than raw meat or chicken. This will prevent raw meat and chicken juices from dripping onto food that's ready-to-eat.
  • Keep your fridge clean, and don't overfill it. This can prevent cold air from circulating properly, which can affect the temperature of food inside the fridge.

 

It's also important to think about how to keep yourself safe when you're away from home.

Travelling/eating out

  • Look at how clean the café or restaurant is.
  • Avoid food, even salad and cold cuts, that sits in a cabinet 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.

The following links provide further information about gastroenteritis. Be aware that websites from other countries may have information that differs from New Zealand recommendations.

Gastroenteritis – causes, symptoms, treatment(external link) Southern Cross, NZ
Gastroenteritis(external link) KidsHealth, NZ
Food and drink considerations when travelling(external link) Centers for Disease Control, US

Apps

Digestive health apps
Nutrition, exercise and weight management apps

Resources

Gastroenteritis (tummy bug) [PDF, 233 KB] Hawkes Bay Public Health Unit, NZ
Viral gastroenteritis(external link) Regional Public Health
Gastroenteritis(external link) Te Whatu Ora, NZ

References

  1. Acute gastroenteritis(external link) Health New Zealand | Te Whatu Ora, 2023
  2. Gastroenteritis (tummy bug) information sheet [PDF, 233 KB] Hawkes Bay Public Health Unit, NZ
  3. Assessment and management of infectious gastroenteritis(external link) BPAC, NZ, 2009
  4. Infectious gastroenteritis(external link) Auckland Region HealthPathways, NZ, 2022
  5. Safe food preparation, cooking and storage at home(external link) Ministry for Primary Industries, NZ, 2024

Brochures

Gastroenteritis
Te Whatu Ora, NZ, 2023

viral gastroenteritis

Viral gastroenteritis
Regional Public Health, NZ, 2017

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Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Dr Emma Dunning, Clinical Editor and Advisor

Last reviewed: