Viruses are thought to be the leading cause of foodborne illness in the United States based on the percentage of people ill, even though there are only a few viruses that are important foodborne pathogens.

Viruses are much smaller than bacteria and cannot live outside a host, such as an animal or the human body. They are not cells but look more like particles (they have a protein coat, not a cell wall); reproducing only when they invade living cells. Although they do not multiply in food products, it can take only a few viral particles to make a person sick. Viruses are easily transferred from one food product to another, from contaminated water to foods, and from infected food handlers to foods. The two most well-known foodborne viruses are Hepatitis A and Norovirus (also known as Norwalk virus). Antibiotic drugs will not help in treatment because antibiotics fight against bacteria not viruses.

What is Norovirus?

Norovirus is a leading cause of foodborne illness. You can get norovirus from contaminated food or water, an infected person, or by touching contaminated surfaces. Norovirus causes inflammation of the stomach, intestines or both. This is called acute gastroenteritis. This leads you to have stomach pain, nausea, diarrhea and vomiting. Quick Facts about Norovirus.

Anyone can be infected with norovirus and get sick. Also, you can have norovirus illness many times in your life. Norovirus is the most common cause of acute gastroenteritis in the United States. Each year, it causes about 21 million illnesses and contributes to about 70,000 hospitalizations and 800 deaths. If you have norovirus illness, you can feel extremely ill and throw up or have diarrhea many times a day. This can lead to dehydration, especially in young children, older adults, and people with other illnesses. Most people with norovirus illness get better within 1 to 3 days, however, it can be serious for some people, especially young children and older adults.

Norovirus and food
Norovirus is a leading cause of illness from contaminated food in the United States.
Foods commonly involved in outbreaks include:

  • leafy greens (such as lettuce, spinach)
  • fresh fruits
  • shellfish (such as oysters)

However, any food served raw or handled after being cooked can get contaminated.

Most common symptoms of Norovirus:

  • diarrhea
  • throwing up
  • nausea
  • stomach pain

Other symptoms:

  • fever
  • headache
  • body aches

Symptoms of dehydration:

  • decrease in urination
  • dry mouth and throat
  • feeling dizzy when standing up

*Children who are dehydrated may cry with few or no tears and be unusually sleepy or fussy.

Treating Norovirus

  • There is no specific medicine to treat people with norovirus illness. Antibiotic drugs will not help because antibiotics fight against bacteria not viruses.
  • If you have norovirus illness, you should drink plenty of liquids to replace fluid lost from throwing up and diarrhea. This will help prevent dehydration.
  • Dehydration can lead to serious problems.
  • Severe dehydration may require hospitalization for treatment with fluids given through your veins (intravenous or IV fluids). If you or someone you are caring for is severely dehydrated, call the doctor.
  • Sports drinks and other drinks without caffeine or alcohol can help with mild dehydration. But, these drinks may not replace important nutrients and minerals.
  • Oral rehydration fluids that you can get over the counter are most helpful for mild dehydration.

For more on preventing norovirus infection.

What is Rotavirus?

Rotavirus is a virus that causes gastroenteritis (inflammation of the stomach and intestines). The rotavirus disease causes severe watery diarrhea, often with vomiting, fever, and abdominal pain. In babies and young children, it can lead to dehydration. Rotavirus is the leading cause of severe diarrhea in infants and young children worldwide.

Rotavirus spreads easily among young children. Children can spread the virus both before and after they become sick with diarrhea. They can also pass rotavirus to family members and other people with whom they have close contact.

Rotavirus is passed from a person’s body into the environment via the feces of infected persons. The virus spreads by the fecal-oral route; this means that the virus must be passed by an infected person and then enter a susceptible person’s mouth to cause infection.

How is Rotavirus spread?
By contaminated
• Food
• Water
• Hands
• Objects (toys, surfaces)

Rotavirus disease is most common in infants and young children, but adults and older children can also become infected with rotavirus.

Once a person has been exposed to rotavirus, it takes about 2 days for symptoms to appear.

Symptoms include:
• Fever
• Vomiting
• Diarrhea
• Abdominal pain

  • Vomiting and watery diarrhea may last from 3 to 8 days in a child who is infected with rotavirus. Additional symptoms include loss of appetite and dehydration, which can be especially harmful for infants and young children.
  • Usually a person’s first infection with rotavirus causes the most severe symptoms. There is no antiviral drug to treat rotavirus infection. Antibiotic drugs will not help; this is because antibiotics fight against bacteria not viruses.
  • Dehydration can lead to other serious problems. Severe dehydration may require hospitalization for treatment with intravenous (IV) fluids (fluids given to the patient directly through their veins).
  • The best way to protect against dehydration is to drink plenty of liquids (oral rehydration therapy).
  • Severe dehydration can be serious. If you think you or someone you are caring for is severely dehydrated, contact your doctor.

About rotovirus.

About rotavirus (Spanish)

I was one of more than 25 individuals who was sickened by a virus-contaminated salad at a work-related banquet in a California hotel. My symptoms of nausea, diarrhea, and painful abdominal cramping were so severe that I went to a hospital emergency room for treatment. This hospital visit was just the beginning of an ongoing battle with food poisoning that caused severe damage to my entire gastrointestinal system.
Barbara
Survivor, Norovirus

What is Hepatitis A?

Hepatitis A (Hep A) is a contagious liver disease that results from infection with the Hepatitis A virus.

Foodborne Hepatitis can range in severity from mild illness to a severe illness lasting several months. 

Hepatitis A is usually spread when the virus is taken in by mouth from contact with food, drinks, or objects contaminated by the feces of an infected person.

+ Contaminated food or water:

  • Hepatitis A can be spread by eating or drinking food or water contaminated with the virus.
  • This is more likely to occur in countries where Hepatitis A is common and in areas where there are poor sanitary conditions or poor personal hygiene.
  • The food and drinks most likely to be contaminated are fruits, vegetables, shellfish, ice, and water.
  • In the United States, chlorination of water kills Hepatitis A virus that enters the water supply.

+ Person to person contact:

  • When an infected person does not wash his or her hands properly after using the toilet and touches other objects or food.
  • When a parent or caregiver does not properly wash his or her hands after changing diapers or cleaning up the stool of an infected person.
  • When someone engages in certain sexual activities, such as oral-anal contact with an infected person.

Treatment for Hepatitis A
There are no special treatments for Hep A.

Most people with Hep A will feel sick for a few months before they begin to feel better. A few people will need to be hospitalized.

Antibiotic drugs will not help; this is because antibiotics fight against bacteria not viruses. During this time, doctors usually recommend rest, adequate nutrition, and fluids.

Does Hep A cause symptoms?
Not always. Some people get Hepatitis A and have no symptoms of the disease. Adults are more likely to have symptoms than children. 

A doctor can determine if you have Hepatitis A by discussing your symptoms and taking a blood sample.

The symptoms of Hepatitis A
If you do have symptoms, they may include the following:
• Fever
• Fatigue
• Loss of appetite
• Nausea
• Vomiting
• Abdominal pain
• Dark urine
• Clay-colored bowel movements
• Joint pain
• Jaundice (a yellowing of the skin or eyes)

Some people do not have any symptoms.

What if a restaurant has an outbreak of Hepatitis A?
Talk to your health professional or a local health department official for guidance. Outbreaks usually result from one of two sources of contamination: an infected food handler or an infected food source.

Your health department will investigate the cause of the outbreak.

Keep in mind that most people do not get sick when someone at a restaurant has Hepatitis A.

However, if an food handler is infectious and has poor hygiene, the risk goes up for patrons of that restaurant.

In such cases, health officials might try to identify patrons and provide Hepatitis A vaccine or immune globulin if they can find them within 2 weeks of exposure.

On rare occasions, the source of the infection can be traced to contaminated food.

Foods can become contaminated at any point along the process: growing, harvesting, processing, handling, and even after cooking.

In these cases, health officials will try to determine the source of the contamination and the best ways to minimize health threats to the public.

CDC/ E.H. Cook, Jr.
CDC/ E.H. Cook, Jr.

I think I have been exposed to Hep A.
If you have any questions about potential exposure to Hepatitis A, call your health professional or your local or state health department.

If you were recently exposed to Hepatitis A virus and have not been vaccinated against Hepatitis A, you might benefit from an injection of either immune globulin or Hep A vaccine.

However, the vaccine or immune globulin must be given within the first 2 weeks after exposure to be effective.

A health professional can decide what is best on the basis of your age and overall health.

How serious is Hepatitis A?
Almost all people who get Hepatitis A recover completely and do not have any lasting liver damage, although they may feel sick for months.

Hepatitis A can sometimes cause liver failure and death, although this is rare and occurs more commonly in persons 50 years of age or older and persons with other liver diseases, such as Hepatitis B or C.

There are five identified types of viral hepatitis and each one is caused by a different virus. In the United States, Hep A, Hep B and Hepatitis C are the most common types.