Salmonella

Salmonella infection is a type of gastroenteritis (‘food poisoning’). Symptoms including diarrhoea and stomach cramps usually appear 6 to 72 hours after becoming infected. Good hygiene can help stop it spreading.

Most people recover from Salmonella without treatment. Staying hydrated, resting and avoiding spreading the infection to others are key to managing salmonella infection.

On this page, you can find the following information:

How is salmonella infection spread?

You can get salmonella from foods contaminated with the bacteria, such as meat, chicken, eggs, milk and fruit and vegetables. People or animals infected with salmonella can pass it on in their faeces (poo) into soil, water and food. The bacteria can also contaminate (make unsafe) surfaces such as toys, bathroom taps or doors and nappy change tables. Salmonella is often spread to humans in the following ways:

Eating contaminated food: This includes undercooked meat, especially chicken, or contaminated raw fruit and vegetables. Contamination of food can also happen when hands are not washed properly after going to the toilet or changing the nappy of an infected infant.
Cross-contamination: Salmonella can spread in the kitchen by cross-contamination from raw chicken meat, including juices from the meat, to other food, utensils (such as cutting boards), food contact surfaces and the hands and clothing of food handlers.
Drinking contaminated water: Drinking contaminated water is responsible for a number of outbreaks globally, such as contamination of water from sewage outflow systems, waste run-off from grazed pasture. You can also get salmonella from swimming or playing in contaminated water, such as rivers and lakes. 
Direct handling of animals: Salmonella are found in the poo of many animals, including farm animals and household pets. It can be spread by handling infected animals and not washing hands afterwards.

Who is most at risk of salmonella infection?

Anyone can get salmonella, but babies, older people and people whose immunity is compromised (through illness or cancer treatment) are most at risk.

Travellers to developing countries where sanitation and food hygiene may be less strict, farm workers, meat processing workers and those who handle raw meat may be more likely to be exposed to salmonella.

Note: There are different strains of Salmonella bacteria. Salmonella typhi causes an infection known as typhoid which can cause serious illness if not treated.

What are the symptoms of salmonella infection?

Salmonella infection is a form of gastroenteritis (gastro). Symptoms of salmonella can include runny poo (diarrhoea), stomach pain or cramps, and feeling or being sick (nausea or vomiting).

Symptoms usually appear 6 to 72 hours after becoming infected. The symptoms usually last between one-to-seven days but in more severe cases they can last up to 10 days.

How is salmonella infection diagnosed?

Most cases of gastro do not require special investigations. If your symptoms are severe or ongoing, or your doctor suspects you might have salmonella, you may be asked to provide a stool (poo) sample. This can be tested in the laboratory for salmonella and other germs.

Salmonella is a notifiable disease. This means that if you are found to have salmonella, your doctor will notify the Public Health Service. Someone from your local public health team may contact you to find out how you picked up the bacteria. This helps them trace the source of infection to reduce the risk of a large outbreak.

How is salmonella infection treated?

Most people will recover without the need for any special medication. You can help your recovery by drinking plenty of fluids to avoid getting dehydrated. Take extra care with young children and older adults who can become dehydrated very quickly. Also, eat as you feel able – be guided by your appetite. Start with bland food such as toast or rice and small, light meals.

Antibiotics

Antibiotics are not commonly needed to treat salmonella infections. They have little impact on how long you are sick or how severe your symptoms are. They may help prevent the spread of the disease by killing the bacteria in your poos. Antibiotics may be considered when symptoms are severe or prolonged, or for people at high risk of complications, such as pregnant women or people with weakened immune systems.

Medicines for diarrhoea

Medicines for diarrhoea, such as loperamide and Diastop®, are not routinely recommended, but may be considered in some circumstances. They must be avoided if you have blood and mucous in your poos. This can make things worse as it can prolong the diarrhoea and there is the risk of the serious complication, toxic megacolon. Medicines for diarrhoea are also not recommended for use in children under 12 years. Before taking them, check with your doctor whether they are safe for you.

How long do I need to take off work or school?

Stay away from school, early childhood centres or work until 48 hours (2 days) after the symptoms have gone and do not have visitors from outside the family.
However, as salmonella infection is a notifiable disease (see diagnosis above) you will need to check with your doctor first.

Do not swim in pools (private or public) for at least 2 weeks after your symptoms have gone.

How can salmonella infection be prevented?

Every year about 200,000 New Zealanders get a food-related illness, of which salmonella infection is one. This is a higher rate than in other developed countries. Because we have a high rate of salmonella infection in New Zealand, and because you can’t tell if a food has been infected with Salmonella bacteria, we all need to take steps to prevent it happening. 

There are several things you can do to help prevent it:

Wash your hands

Wash your hands thoroughly by using plenty of soap and hot water, cleaning between your fingers and under your fingernails, rinsing well and drying your hands on a clean dry towel or paper towel. Do this:

  • before and after preparing food
  • after going to the toilet or changing a baby’s nappy
  • after caring for people who are ill
  • after playing or working with animals.

Clean surfaces and toys

Regularly clean, sanitize, or disinfect toys and surfaces. These may  become contaminated with Salmonella bacteria, for example, if someone in your family has been infected, or if you have pets in your house.

Food preparation

Take care when preparing food, cook food well, watch what you eat and wash your hands frequently and properly. Use different chopping boards, trays, utensils and plates when preparing raw foods and ready-to-eat food. If you have only one chopping board wash it well in hot soapy water before reuse.

  • Clean: keep all food preparation areas, utensils and equipment clean. Wash raw vegetables properly.
  • Cook: raw foods well and leftovers until steaming hot. Ensure minced meat, chicken and sausages are cooked thoroughly until juices are clear. Thorough cooking of food kills Campylobacter. 
  • Cover: all foods in the fridge, cupboard and outdoors. Separate and store raw and cooked foods so there is no chance of cross-contamination.
  • Chill: store ready-to-eat food between 0-4°C. Any leftover cooked food should be covered and chilled (within 2 hours). 

See also: Food safety tips NZ Food Safety Authority 

If your water source is believed to be contaminated, you must boil all water for 1 minute before drinking, making up infant formula, food preparation and cleaning teeth. See also Water in rural areas (HealthEd, NZ) and food safety tips at home.

Learn more

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

Salmonella Auckland Regional Public Health Service
Tips for food safety
Ministry for Primary Industries, New Zealand, 
Salmonella Centers for Disease Control and Prevention

References

  1. Assessment and management of infectious gastroenteritis BPAC, NZ, 2009
  2. Campylobacter, E. coli and salmonella HealthEd, NZ, 2016
  3. Salmonella (Salmonellosis) Auckland Regional Public Health Service   
Credits: Health Navigator Editorial Team. Last reviewed: 23 Sep 2021