Escherichia coli (STEC) infection: symptoms and advice

Escherichia coli (E. coli) is a bacterium that normally lives in the intestines of people and other warm-blooded animals. Although most strains of E. coli are harmless, some types can cause illness. Find out about how E. coli strains can make you ill and how to avoid infection.

What types of E. coli cause illness?

E. coli form an important part of a healthy human intestine, producing vitamin K and helping prevent colonisation by disease-causing bacteria. However, some strains can cause illness.

The harmful strains are known as Shiga toxin-producing E. coli (STEC), also called verocytotoxigenic E. coli (VTEC).

Harmful STECs are generally identified by their subgroup, and there are more than 200 of these. E. coli O157:H7 causes the vast majority of human illnesses.

Symptoms of STEC infection

STEC infections typically cause mild or severe diarrhoea and stomach cramps 3 to 9 days after the bacteria are consumed.

Most patients recover within 10 days. However, a small proportion (usually infants and frail, elderly people) develop life-threatening conditions such as acute kidney disease. Most people with kidney disease recover completely. While deaths do occur, they are rare.

How you can be exposed

Because E. coli live in the gut of humans and animals, they can contaminate farm, water catchment and food processing environments through faeces, and can subsequently contaminate foods. Food hygiene controls are designed to prevent, or minimise, such food contamination.

The main source of STEC is believed to be cattle and sheep, which are not affected by the bacteria. STEC illnesses in New Zealand have been mainly associated with farm environments, farm animal contact, and consumption of untreated water or raw (unpasteurised) milk.

In other countries humans have been infected with STEC from contaminated foods like raw or undercooked ground meat products, raw milk and contaminated raw vegetables, in particular leafy greens and seed sprouts. Undercooked meat has not been associated with STEC illness in New Zealand.

Person-to-person transmission can occur if infected people do not wash their hands properly after using the toilet.

How to avoid STEC infection

  • Cook all minced meat patties and sausages thoroughly, and do not eat undercooked minced products.
  • Use a meat thermometer to check that the internal temperature is higher than 70 degrees Celsius. If you don't have a thermometer, make sure the cooked meat is brown throughout (not pink), and the juices run clear.
  • Wash leafy green salad vegetables before use.
  • Avoid raw drinking milk, unpasteurised dairy products, and unpasteurised juices.
  • Beware of untreated non-tank water at farms.
  • Wash your hands immediately after touching animals or handling at-risk foods like raw meat and unpasteurised milk.
  • Make sure you, and those around you, wash your hands carefully with soap after using the toilet to reduce the risk of spreading the disease.

Always wash your hands with soap and dry them carefully before touching food. This is especially important for children in at-risk environments, such as farms, petting zoos, school fairs, agricultural shows – or at anywhere there are, or have been animal faeces.

Find out more

Last reviewed: