MSU Extension Food Safety

Viruses differ from other foodborne pathogens because they are very small and need a living host to survive. For viruses to reproduce, they take over healthy cells and use the energy from the healthy cell to create virus cells to reproduce and infect other cells. The Michigan Department of Health and Human Services (MDHHS) shares that foodborne viruses are spread through contaminated food, contaminated water or poor personal hygiene by the person preparing the food (e.g. improperly washing hands after using the restroom or after coming in contact with an infected person’s feces or vomit). According to the Centers for Disease Control and Prevention (CDC), norovirus is the leading cause of foodborne illness outbreaks from contaminated food in the U.S. and is highly contagious. While highly contagious like norovirus, hepatitis A is less common in the U.S. and more common in economically challenged countries according to the World Health Organization (WHO).

According to the CDC, norovirus is an acute gastrointestinal illness leading to inflammation of the stomach or intestines, sometimes both. Norovirus is the leading cause of illness and outbreaks from contaminated food in the United States and causes 19-21 million illnesses, 109,000 hospitalizations and 900 deaths each year. Norovirus was previously known as Norwalk Virus and is sometimes referred to as ‘the cruise ship virus’ because of the increased likelihood of contact with the virus within a closed group on board cruise ships. Health officials also closely monitor illnesses on cruise ships, so the public is more likely to hear of a norovirus outbreak on a cruise ship than in other locations.

According to the CDC, hepatitis A is a liver disease that is the result of the hepatitis A virus. Hepatitis A can cause epidemics worldwide, leading to cyclical recurrences. These recurrences are more likely to affect developing countries due to increased likelihood of contaminated drinking water and poor sanitation. The hepatitis A virus can range in severity from a mild illness lasting several weeks to a more severe illness lasting several months. Fortunately, there is a vaccine for hepatitis A available for those 12 months and older, anyone traveling to certain high-risk countries, or people at higher risk for infection. According to the U.S. Department of Health and Human Services (DHHS), once someone has hepatitis A, their body develops antibodies that prevent them from getting the virus again.

How do you catch it?

Norovirus and hepatitis A can both be contracted by ingesting small particles of feces through consumption of contaminated food or water. Norovirus outbreaks may occur in food service settings, caused by infected food service workers touching raw, ready-to-eat foods with their bare hands that have not been properly washed. Norovirus is also able to live on surfaces contaminated with the virus and can be spread when an uninfected person or food touches that surface. Shellfish from contaminated waters can also be a source of norovirus. Norovirus spreads quickly in enclosed places with a lot of contact among groups of people like day care centers, schools, nursing homes and on cruises. In the United States, most norovirus outbreaks occur from November to April and during cooler months when people are more likely to be indoors. Norovirus changes its form every time it is passed from person to person, and our body does not recognize the new form of norovirus so we can become ill again.

Some of the sources of hepatitis A include raw and ready-to-eat foods, raw or undercooked shellfish, contaminated drinking water and cooked foods not reheated after contact with an infected food handler. Symptoms of hepatitis A usually appear within two-to-six weeks and can develop over a period of several days. Additionally, people can spread the virus for up to two weeks without showing symptoms so it is possible to catch the virus from someone who is not yet aware that they are ill. This may be most true with children under 6 years old because the majority of them do not show symptoms, according to the U.S. DHHS.

Symptoms and Duration

Norovirus

• Diarrhea, vomiting, nausea, stomach pain
• Diarrhea is more common in adults and vomiting is more common in children
• Incubation period lasts 12-48 hours
• Usually lasts one to three days, though norovirus can last 4-6 days in high-risk populations (older adults, young children and hospitalized individuals)

Hepatitis A

• Jaundice, diarrhea, dark urine, fever, headache, nausea, abdominal pain, loss of appetite
• Incubation period averages 28 days, ranging from 15-50 days
• Duration varies from two weeks to six months in more severe cases

Who is most at risk?

People that work or spend large amounts of time in closed environments are most at risk for norovirus. This includes nursing homes, day care centers, schools and cruise ships. Norovirus can lead to dehydration from vomiting or diarrhea and young children, older adults and those already sick with another infection are most at risk for severe symptoms. Norovirus is considered very common and the CDC estimates that most individuals will have norovirus about five times during their lifetime.

Most people in the United States are vaccinated against hepatitis A around 12 months of age but there are some groups that have a higher risk of infection worldwide. These include those who travel or live in countries where hepatitis A is common, family members or caregivers of a recent adoptee from a country where hepatitis A is common, those who live with someone who has hepatitis A and those who have blood-clotting disorders like hemophilia. While most people infected with hepatitis A recover without complications, liver failure and sometimes death can occur. These more severe outcomes are rare among healthy individuals and are seen more commonly in those aged 50 and older and when combined with other liver diseases like hepatitis B or C.

How to prevent it

Norovirus

• Wash hands thoroughly, especially after restroom use and before prepping food.
• Clean and disinfect surfaces contaminated by vomiting or diarrhea using a bleach-based cleaner (1000-5000ppm or 5-25 tablespoons bleach per gallon of water). Also, clean and disinfect food contact surfaces.
• Avoid food prep for others if vomiting or ill with diarrhea.
• Wash fruits and vegetables thoroughly before eating.
• Cook oysters and other shellfish to safe internal temperatures (at least 145°F) before eating. The CDC cautions that norovirus has been found to survive at 145°F so it is also important to take multiple prevention measures like purchasing from approved suppliers and practicing good personal hygiene.
• Wash clothing soiled by vomit or feces immediately to minimize spread of virus.
• Stay home for at least 48 hours after symptoms stop if working in a food service establishment to prevent spread of norovirus to others.

Hepatitis A

• Get vaccinated because Hepatitis A is one of the few foodborne pathogens with an associated vaccine. The CDC shares additional hepatitis A vaccine resources including who should get it, what to expect, safety and effectiveness.
• Wash hands thoroughly for 20 seconds with clean, soapy water after using the bathroom, changing a diaper, or before preparing food.
• Avoid raw shellfish, raw oysters, or other undercooked shellfish, particularly if you are in a high-risk population.

Check out other articles in this series to learn more about the Big 6 Pathogens from Michigan State University Extension.

Other articles in this series

• Introduction
• E. coli
• Salmonella
• Shigella