Salmonella infection is a type of food poisoning. Most people develop symptoms including diarrhoea, fever and abdominal cramps 12 to 72 hours after eating contaminated food.
Key points about salmonella
- You usually get salmonella infection by eating food contaminated with Salmonella bacteria.
- Symptoms usually last for 4 to 7 days and most people recover without treatment.
- Staying hydrated, resting and avoiding spreading the infection to others are key to managing salmonella infection.
- Prevention involves following food safety and handwashing guidelines.
- There are different strains of Salmonella bacteria. Salmonella typhi causes an infection known as typhoid which can cause serious illness if not treated.
How is salmonella infection spread?
Salmonella bacteria live in the gut of animals, so they can affect meat, chicken, eggs and milk. Other foods, such as fruit and vegetables, can also get contaminated through contact with faeces (poo) in soil or water. Infected people or animals pass Salmonella bacteria in their faeces (poo) into soil, water and food. The bacteria can also pass into and contaminate (make unsafe) surfaces such as toys, bathroom taps or doors and nappy change tables. You get infected by swallowing the bacteria.
This can happen when you:
- handle raw meat or poultry
- eat contaminated raw or under-cooked food
- eat contaminated bought food, such as takeaways or restaurant food
- drink contaminated water
- drink raw milk or raw milk products
- have contact with faeces, for example, when you change a nappy
- have contact with infected animals, especially puppies and kittens with diarrhoea, tropical fish and reptiles
- have contact with the manure from farm animals
- swim or play in contaminated water, such as rivers and lakes
- travel overseas (one of the causes of traveller’s diarrhoea).
Anyone can get salmonella, but babies, older people and people whose immunity is compromised (through illness or cancer treatment) are most at risk.
What are the symptoms of salmonella infection?
Symptoms can include:
- diarrhoea, which may have blood in it
- stomach pain or cramps, which may be severe
- flu-like symptoms, including headache, muscle pains, fever and fatigue (feeling very tired)
- nausea (feeling sick)
- vomiting (being sick).
Symptoms usually appear 12 to 72 hours after you get infected. The symptoms usually last between 1 and 7 days, but in more severe cases they can last up to 10 days.
How is salmonella infection treated?
Salmonella does not usually cause a severe or long-lasting illness. You will normally be better within 2 weeks. However, some people, especially young children and older people, can get very ill as they are more likely to become dehydrated. They may need hospital treatment.
The main treatment is to rest and have extra fluids, to prevent dehydration. Try to drink small amounts of water often. Oral rehydration solutions (available from pharmacies) are useful because they also replace vital salts. Avoid fizzy or sugary drinks (including fruit juice), milk and alcohol. For 48 hours, eat bland, non-greasy foods or soups and avoid grains, uncooked fruits and vegetables.
If your symptoms are severe, you should see your doctor, who may also prescribe medicine.
How is salmonella infection diagnosed?
To get a diagnosis, you need to see your doctor. They will probably ask you to provide a specimen (a small amount) of your faeces (poo) so it can be tested. Your doctor will tell you how to collect the specimen and what to do with it.
Salmonella is a notifiable disease. This means that if you have salmonella, your doctor will tell your local Public Health Service (PHS). The PHS may contact you to find out how you were infected. This helps to prevent more cases of the infection.
How long will I be infectious?
You will be infectious as long as the Salmonella bacteria is in your system. This varies from person to person and can range from a few days to several weeks from when the diarrhoea started. It's important to take extra care to not pass on the infection during this time.
How can I care for myself with salmonella?
- If your doctor prescribes medicine, make sure you take it as instructed.
- Drink plenty of water or oral rehydration solution while you have diarrhoea (runny poos) or vomiting (throwing up).
- If your child is ill and is not able to drink, go back to your doctor.
- Stay away from school, early childhood centres or work until at least 48 hours (2 days) after your symptoms have gone.
How can I prevent salmonella?
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.
Regularly clean areas and surfaces (including toys) that may have become contaminated with Salmonella bacteria, for example, if someone in your family has been infected, or if you have pets in your house.
- Thaw meat in the fridge and not at room temperature.
- Keep raw meat covered and separate from other foods, and store at the bottom of the fridge.
- Use separate chopping boards when preparing raw foods and cooked foods, or wash the board in hot soapy water between preparing raw and cooked foods.
- Cook chicken thoroughly until the juices are clear.
- Cook all minced meat patties and sausages thoroughly.
- Avoid drinking raw milk and raw milk products.
- Avoid eating shellfish that has been gathered from contaminated waters.
- Wash fruit and vegetables before use.
If you have salmonella, avoid preparing food for other people. If you must do so, wash and dry your hands well first.
Avoid drinking water that has not been treated, including water from lakes, rivers or streams. If in doubt, make the water safe by boiling it or by installing an appropriate disinfection/filtration (treatment) unit.
If you have to drink untreated water that is taken from a roof, river or lake (eg, in a rural area), it should be boiled for 1 minute or put through an appropriate treatment unit.
Don’t go swimming in a pool if you have diarrhoea. You need to wait at least 2 weeks after the symptoms have gone. If you or a child are unwell then do not share bathwater, as this can easily pass the infection on.
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 Regional Public Health, Greater Wellington Region
Tips for food safety Ministry for Primary Industries, New Zealand, 2017
Salmonella infection NHS Choices, UK, 2017
Salmonella Patient Info, UK, 2016
- Assessment and management of infectious gastroenteritis BPAC, NZ, 2009
- Campylobacter, E. coli and salmonella HealthEd, NZ, 2016
- Salmonella (Salmonellosis) Auckland Regional Public Health Service