Food infection / Food poisoning



Food poisoning is caused by consuming food contaminated with bacteria, or their toxins, or viruses. It usually does not cause severe ailments (symptoms) and most people recover within days without the need for treatment.

In most cases of food poisoning, the food is contaminated with bacteria, such as salmonella, campylobacter or Escherichia coli, or by viruses, such as norovirus.

Signs and symptoms

The disorders (symptoms) related to food poisoning usually begin a few hours up to one or two days after eating the contaminated food (sometimes it can also take several days or several weeks).

The main symptoms (symptoms) are:

  • nausea
  • He retched
  • diarrhea (also with blood or mucus)
  • stomach cramps and abdominal pain
  • weakness
  • loss of appetite
  • fever
  • sore muscles
  • chills

What to do

Most people with food poisoning recover at home and do not need any specific treatment, although there are some situations in which it is advisable to contact the doctor.

In the early stages, when the complaints (symptoms) are more intense, it is advisable to rest, reduce or avoid eating solid foods and take care to drink fluids to prevent dehydration. In this regard, it is useful to drink a lot of water, even just sipping it.

When you feel better, you can have small light meals, such as toast, crackers, bananas and rice.

You can use a oral rehydration solution (after consulting your doctor if you have kidney disease) available at pharmacies and especially recommended for the most vulnerable, such as the elderly and those suffering from other diseases.

When to see your doctor

You should contact your doctor in the presence of:

  • fever, over 38.5 ° C (measured with thermometer)
  • vomiting, which persists and does not allow the intake of liquids
  • diarrhea, which does not improve after three days
  • signs of severe dehydration, such as confusion, rapid heart rate, sunken eyes, and reduced or no urine
  • neurological disorders, such as headache, cervical stiffness, confusion, loss of balance and dizziness, convulsions as well as fever and muscle aches

Some categories of people like:

  • individuals over 65 years of age
  • children under the age of 5
  • individuals with weakened immune systems due to diseases such as cancer, diabetes, liver or kidney disease, HIV / AIDS infection, alcoholism
  • people who use drugs antacids or who have undergone chemotherapy or radiotherapy treatments
  • pregnant women

they have a higher risk of getting food poisoning and, when this happens, of developing the disease in a severe form.

Types of Infection

Food contamination is usually caused by bacteria, but can also sometimes be caused by viruses or parasites.

Contamination by bacteria


Bacteria are usually found in raw or undercooked meat (particularly poultry), raw unpasteurized milk and raw water.
The incubation period (the time between eating contaminated food and the onset of the disturbances) for food poisoning caused by Campylobacter is usually between two and five days. The disturbances generally last less than a week. .


Bacteria are often found in raw or undercooked meat, raw eggs, milk and other dairy products.
The incubation period is typically between 12 and 72 hours. Disorders (symptoms), diarrhea, nausea, vomiting, fever, abdominal cramps, usually last four to seven days.


Bacteria can be found in a range of refrigerated foods "ready for consumption", including pre-made sandwiches, pates and soft cheeses (such as brie or camembert).
All of these foods should be consumed within the expiration dates.
The incubation period can vary considerably, from a few days to several weeks. Intestinal disorders (symptoms) are mild and usually heal within 3 days, while other disorders may appear in pregnant women, people with a weakened defense system (immune system) or over 65 years of age. (symptoms), even after a few weeks from the intake of contaminated food, which require a consultation with your doctor.
In particular, in pregnant women, flu-like disorders can occur, with fever and joint pain, but risks to the fetus can occur: abortion, premature birth and infection of the newborn.
Neurological disorders such as headache, cervical stiffness, confusion, loss of balance and dizziness, convulsions as well as fever and muscle aches may occur in people with immunosuppression or in the elderly over 65 years of age.

Escherichia coli

Bacteria are present in the intestines of many animals, including humans. Most bacterial strains are harmless, but some can cause serious illness.
Most cases of food poisoning caused by E. coli occur after eating undercooked meat, fresh vegetables and sprouts, unpasteurized drinks, unpasteurized raw milk.
The incubation period is typically 1 to 8 days while complaints (symptoms) usually last for a few days or weeks.
In some cases, when the infection is caused by certain Escherichia coli bacteria that produce specific toxins (shiga-toxins) and children under 5 years old, or the elderly over 65 years are affected, more serious disorders such as painful abdominal cramps, diarrhea may appear. often with blood and vomit. Sometimes, very serious complications (haemolytic uremic syndrome) can occur that require urgent specialist medical treatment.


Bacteria can contaminate any food washed using contaminated water, especially fruit and vegetables.
Disorders (symptoms) typically develop within 7 days of consuming contaminated food and last up to a week. They are characterized by abdominal cramps, diarrhea often with blood and mucus, and fever.

Other toxin-producing bacteria

Bacillus botulinum (botulism)

Bacillus cereus

Food poisoning is caused by the ingestion of pre-formed toxins in food. This occurs when food, especially after cooking it, is not stored properly (i.e. it has not been stored in the refrigerator at a low temperature). This allows for the growth of bacteria and the production of toxins.
There are two types of heat-stable toxin that cause vomiting or diarrhea, respectively. Vomiting is associated with the consumption of starchy foods (rice, potatoes); diarrhea from eating meat, both of which are contaminated with spores. Disorders arise very quickly (after 1-6 hours on average) and last about 24 hours, but can cause severe dehydration.

Staphylococcus aureus (enterotoxigenic strain)

It is the most frequent cause of food poisoning (poisoning).Staphylococci can contaminate foods rich in proteins (egg-based products, dairy products, cured meats, creams, meats) which, kept at room temperature, allow bacteria to grow and produce a "thermostable enterotoxin responsible for the disturbances. In man" they manifest themselves. 1-6 hours after ingestion of contaminated food and consist of vomiting, abdominal cramps and diarrhea. They are short-lived (24-48 hours) but can cause severe dehydration.

Clostridium perfringens (producer of type A enterotoxin)

Bacteria, in the form of spores, mainly contaminate meat-based foods. The spores are not destroyed by cooking and, once ingested, in the distal part of the intestine they are transformed into bacteria that produce enterotoxin. After an incubation of 8-16 hours, diarrhea appears which usually heals in a short time.

Virus contamination


It is a very common virus that causes epidemics in hospitals, schools, hotels. It spreads easily from person to person through contaminated food or water. The most frequent foods as a source of infection are raw crustaceans, especially oysters, and frozen berries. The virus also contaminates the environments (bathrooms, floors) where it remains for a long time and can cause infections by contact with contaminated surfaces.
The main complaints (symptoms) it causes are nausea, vomiting, diarrhea and abdominal cramps; sometimes flu-like disorders such as fever, usually not elevated, muscle aches and fatigue also appear. The incubation period lasts 12-72 hours and complaints usually pass within 24-48 hours.

Contamination by parasites

In Italy, food poisoning caused by parasites is rare, while it is much more common in developing countries.

Parasitic infections that can be spread in contaminated food are:

  • giardiasis
  • cryptosporidiosis
  • amoebiasis

Disorders (symptoms) that occur in food poisoning caused by parasites usually develop within 10 days of consuming contaminated food or water. Sometimes, however, it can take weeks for them to appear. Left untreated, they can last a long time, sometimes several weeks or even months.


Food poisoning can usually be treated at home without consulting a doctor. Most people get better within a few days.

It is important to avoid dehydration by drinking plenty of water as it is necessary to replace the fluids lost through vomiting and diarrhea.

It is also necessary:

  • rest as much as possible
  • eat whenever possible, limiting yourself to light foods (e.g. crackers, rice and bananas)
  • avoid alcohol, caffeine, carbonated drinks, and spicy and fatty foods

You should contact your doctor if you have:

  • fever, over 38.5 ° C (measured with thermometer)
  • persistent vomiting, which does not allow you to drink liquids
  • diarrhea, which does not improve after three days
  • signs of severe dehydration, such as confusion, rapid heart rate, sunken eyes, and reduced or no urine
  • neurological disorders, such as headache, cervical stiffness, confusion, loss of balance and dizziness, convulsions as well as fever and muscle aches
  • pregnancy

Prevent the spread of infection

If you are affected by a food poisoning it is advisable to:

  • avoid preparing food for other people
  • limit contact with the weakest individuals to a minimum, such as the elderly or young children
  • avoid going to work or school before 48 hours have passed after the last episode of diarrhea

Furthermore it is necessary:

  • make sure everyone in the house wash their hands regularly with soap and warm water, especially after going to the bathroom and before and after preparing food
  • disinfect frequently the toilet seat, tubs and taps
  • make sure each cohabiting person has their own towels
  • wash the laundry of the infected person by setting the washing machine to the hottest temperature

The oral rehydrating solutions

The oral rehydrating solutions they are recommended for people, such as the elderly and the chronically ill, who are most at risk of dehydration. They are available at drugstores, dissolve in water and help supplement the minerals, glucose and other important compounds that the body loses due to diarrhea and vomiting.

If you have kidney disease, some types of oral rehydration salts may not be suitable; ask your pharmacist or doctor.

Further treatments

If the complaints are severe or persistent or if you are vulnerable to severe infections, it may be useful to do some in-depth tests.

If the vomiting is particularly severe, drugs to stop the vomiting (antiemetics) may also be prescribed.

In some cases, you may need to be hospitalized for a few days so you can be monitored and replenished intravenously.

Probiotics and lactic ferments can help replenish the intestinal microbial flora (the "good" bacteria found in the intestine) modified during the disease and can also accelerate the disappearance of the disorders. use on a case-by-case basis.

Report of food poisoning

If it is believed that the food poisoning was caused by a food consumed in a restaurant or purchased in a store, it is advisable to report it to the ASL.


Ministry of Health. Food poisoning from natural toxins: a guide to recognition and prevention

Tuscany region. Guidelines for the correct management of episodes of food-borne illnesses

Graziani C, Serra R, Busani L. Surveillance and diagnostics of acute gastroenteritis in Italy.Rome: Higher Institute of Health; 2012 (ISTISAN Reports 12/38)

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