Viruses are a leading cause of foodborne illness in the United States. According to the Centers for Disease Control and Prevention (CDC), viruses account for more than 50% of foodborne disease. Annually, Norovirus causes about 21 million illnesses and contributes to about 70,000 hospitalizations and 800 deaths.
Norovirus and Hepatitis A are the two main viruses of concern for the food industry. Over the past several years, a number of Norovirus and Hepatitis A (HAV) outbreaks have been linked to a wide variety of foods, including berries, pomegranate seeds and oysters. While both viruses are transmitted via the fecal-oral route, they have very different durations and symptoms.
How do foodborne viruses spread?
Norovirus (NoV), also called the Norwalk Virus, is the most common cause of acute gastroenteritis in the U.S. Norovirus illness spreads easily and is often mistaken for the stomach flu. People who are infected with Norovirus can spread it directly to other people, or can contaminate foods they prepare. The virus can also survive on contact surfaces or spread through contact with an infected person.
Most Norovirus outbreaks occur in food service settings such as restaurants and cafeterias. Infected food handlers are frequently the source of the outbreaks, often by touching ready-to-eat (RTE) foods such as raw fruits and vegetables with their bare hands. However, any food served raw or handled after being cooked (even in the production facility) can become contaminated. Foods that are commonly involved in outbreaks of Norovirus illness are:
- Leafy greens
- Fresh fruits and vegetables
- Herbs and spices
- Shellfish (such as oysters)
- Any food that is served raw or handled after being cooked
HAV infection is primarily transmitted via the fecal-oral route, by person-to-person contact or consumption of contaminated food or water. Foods commonly associated with HAV infection include:
- Raw or undercooked shellfish from contaminated waters
- Raw produce
- Contaminated drinking water
- Uncooked foods and cooked foods that are not reheated after contact with an infected food handler
What are the symptoms?
The symptoms of NoV include: low-grade fever, fatigue, abdominal cramps, vomiting, nausea, muscle aches, chills, headache and watery diarrhea. These symptoms generally last 24-48 hours. The infectious dose of this virus is typically very low – from 1-10 virus particles.
HAV is a liver disease that results from infection with exposure to a low dose of virus particles (1-100). Severity of illness from HAV can range from a mild illness lasting a few weeks to a severe illness lasting several months. Symptoms of HAV include: fever, fatigue, abdominal discomfort, nausea, vomiting, joint pain, loss of appetite, jaundice, clay-colored bowel, dark urine and joint pain. HAV is usually spread when a person ingests fecal matter, even in microscopic amounts — from contact with objects, food, or drinks contaminated by the feces of an infected person (typically from improper hand washing).
One major difference between these foodborne viruses is that once a person has been infected with Hepatitis A, the body develops antibodies that will protect them from the virus for life. HAV is one of the few foodborne illnesses that can be prevented by vaccination. Vaccination is recommended for travelers to certain countries and for people at high risk for infection with the virus.
How can you eliminate the spread of viruses?
The best way to eliminate the spread of NoV and HAV is with proper hand washing – washing with plain soap and water for 20 seconds. The efficacy of alcohol-based hand sanitizers to prevent the spread of these viruses is controversial. There is mixed evidence, using surrogate viruses, that alcohol based sanitizers should not be considered a substitute for soap and water.
When it comes to sanitization in the food plant, sodium hypochlorite (chlorine bleach) is recommended after proper sanitization with soap and water. However, an extremely high bleach concentration is recommended for the elimination of HAV and NoV in the plant environment. 1000 – 5000 ppm of bleach is recommended for hard, nonporous surfaces.
What virus testing methods are currently available?
Typically, viruses are present in foods in low numbers, making their detection in traditional cell cultures difficult. Recent diagnostic advances, such as real time RT-PCR, have greatly advanced the detection of foodborne viruses. With RT-PCR, the detection of Norovirus (GI and GII) and Hepatitis A is 1-10 copies depending on the quality of the RNA purification from the food matrix.
Silliker’s new virus laboratory, located in Crete, IL offers qualitative testing for Norovirus GI/GII and Hepatitis A in a number of matrices including: fruits, vegetables, herbs, spices, shellfish, water and environmental swabs. The testing method used was adapted from ISO 15216-2.