The Centers for Disease Control and Prevention (CDC) estimates that each year 76 million – or one out of every four – Americans are sickened as a result of consuming contaminated foods or beverages. Some become seriously ill; 325,000 require hospitalization and 5,000 die. Older adults, young children, and those who have weakened immune systems are particularly vulnerable.
More than 250 different foodborne diseases have been identified. Most of these diseases are infections caused by a variety of bacteria, viruses, and parasites.
Foods that are contaminated with poisonous chemicals or harmful substances can also cause illness. Symptoms of foodborne illness vary by disease but the most common are nausea, vomiting, abdominal cramps, and diarrhea.

I have some of the symptoms described. Do I have a foodborne illness?
Possibly. For example, scientists estimate that 35% of diarrheal illness is caused by a foodborne pathogen. Diarrhea that is caused by food poisoning usually lasts one week or less. Symptoms that appear suddenly are a sign of foodborne illness, although the last food consumed is not necessarily the cause of illness. Different microbes have different incubation periods. The incubation period refers to the time between ingestion and onset of symptoms.
Incubation Periods of Common Foodborne Pathogens
PATHOGEN INCUBATION PERIOD
Staphylococcus aureus1 to 8 hours, typically 2 to 4 hours.
Campylobacter 2 to 7 days, typically 3 to 5 days.
E. coli O157:H7 1 to 10 days, typically 2 to 5 days.
Salmonella 6 to 72 hours, typically 18-36 hours.
Shigella 12 hours to 7 days, typically 1-3 days.
Hepatitis A 15 to 50 days, typically 25-30 days.
Listeria 3 to 20 days, typically 14 days
Norovirus 24 to 72 hours, typically 36 hours.

How can I find out if I am sick because of something I ate or drank?
Foodborne infections are usually diagnosed by laboratory tests that identify the organism. Bacteria such as E. coli O157:H7, Salmonella, Shigella, and Campylobacter are found by microbiologic testing of the ill person’s stool. Parasites can be identified by examining stool specimens under the microscope. Laboratory testing to detect viruses requires stool specimens or serum derived from blood samples. Many foodborne infections are not detected through routine laboratory procedures and health care providers must order appropriate testing before the cause can be identified.
Should I see a doctor if I think I have a foodborne illness?
A person with symptoms of a foodborne illness should seek prompt medical attention if there is blood in the stools, if they are experiencing prolonged vomiting or show signs of dehydration, if diarrhea last 3 days or more or if diarrhea lasts more than 3 days. Anyone at risk for serious consequences – the very young, the very old, or those with immune impairment – should consult a health care provider if symptoms do not improve after 24 hours.
What else should I do?
If you think you have a foodborne illness contact your local health department. They will ask you questions about your symptoms, when they started, and what you have eaten for several days prior to symptom onset. Because some of the organisms that cause illness can be spread by ways other than food, they will ask you about other potential sources such as contact with others with similar symptoms or exposure to animals. This distinction is important so that public health authorities can if necessary, take steps to stop others from becoming ill.
If you know others who have similar symptoms, urge them to contact the health department. Oftentimes, information compiled from a group of individuals provides clues to the source of illness that can be missed when only one person reports to the health department.
If you suspect that your illness is food related, keep any left over food for possible testing. If laboratory tests show the food was contaminated, you will have powerful evidence that the food is the likely cause of your illness. The health department will advise you about any laboratory tests that should be conducted and how long food should be kept. Similarly, keep retail or restaurant receipts showing that you purchased the suspected food. Receipts often contain valuable pieces of information about a food product that the consumer does not know or cannot recall.
Common myths of foodborne illness
As you attempt to determine if you have a foodborne illness and what the potential source could be, avoid these common misconceptions.
The last thing I ate is what made me sick.
Not necessarily. Refer to the table that shows how long it takes for certain microbes to grow inside your body and cause illness. Write down what you ate, where you ate, and when you ate in as much detail as possible. Health department investigators will ask you for this information and accurate recall is critical.
If other people ate what I ate and did not become ill, that particular meal could not be the source of my illness.
Not necessarily. It is well documented that microbes that cause foodborne illness are not always uniformly distributed in a food item. Also, people have different immune systems. One person may consume hamburger prepared from a package of ground beef and become seriously ill with E. coli O157:H7 or Salmonella while his dining companion consumes ground beef from the same package and remains healthy.