Norovirus fact sheet

General
Noroviruses are common worldwide and are one of the most frequent causes of gastrointestinal illness. Infection occurs via contaminated food or water or via smear (fomite) and person-to-person transmission. Most norovirus infections are caused by smear (fomite) transmission. The disease is characteristically manifested by sudden, forceful vomiting, nausea and occasionally stomach cramps. Noroviruses are robust and can withstand cold temperatures. Outbreaks occur predominantly seasonally in the winter months.

Properties

• Virus (pathogen)

Origin / Occurrence

• Worldwide distribution in animals and humans
• Noroviruses can be present on contaminated raw foods (e.g., seafood, fruits and vegetables), in contaminated water, and on contaminated surfaces

Significance

• Stool or vomit of infected persons are common sources of norovirus. Transmission then often occurs via contact, smear (fomite) or droplet infection, and can also occur via the airborne route through aerosols. Furthermore, transmission can occur through consumption of contaminated food or contaminated water
• Infectivity of noroviruses is very high, as a small number of viral particles can cause disease. In addition, they are easily transmissible and show high resistance to disinfectants, environmental influences and heat
• Noroviruses are often the cause of group outbreaks in, for example, nursing homes, hospitals, day-care centers and cruise ships

Clinical picture

• Low minimal infectious dose: approx. 10–100 viral particles
• Incubation period: 12–72 hours
• Duration of illness: 1 to 3 days
• Symptoms: vomiting, nausea, diarrhea, occasionally stomach cramps. Less common symptoms are low-grade fever, chills, headache, muscle pain and fatigue
• A possible consequence is a significant disturbance of electrolyte and fluid balance, which can cause complications especially in small children or elderly patients
• After recovery from an infection only short-lived immunity exists

Examples of affected foods

• Contaminated seafood (e.g., mussels, oysters)
• Vegetables, salads, fruits (due to field fertilization with feces or irrigation with fecally contaminated water)
• Contaminated drinking water
• Foods contaminated by excretions

Stability

• Replication is only possible in host cells in humans
• Viruses cannot multiply in food and drinking water, but can remain infectious for an extended period
• Temperature:
  • Viruses can remain infectious for long periods at refrigerator and freezer temperatures (−18 °C)
  • Increasing inactivation above +60 °C
• Sensitive to low pH values and dryness

Inactivation by heating

• At +85 °C for at least 2 minutes exposure time the viruses are inactivated (Attention: check core temperature)

1. Train staff regarding potential faults and improvement measures
2. Regular cleaning and disinfection of hands and regular glove changes
3. Regular change of work clothing. Ensure work clothing is kept clean
4. Train staff on the requirements for infection control
5. Effectiveness control by visual on-site inspections and follow-up testing

Deficiencies in infection control:
This creates the risk of transmission of pathogenic microorganisms from people to product-contact surfaces or directly to food

Examples:

Salmonella from excretions or infected employees

Staphylococcus aureus from employees with inflamed or purulent wounds or colonization of the nasopharynx

1. Employees who are ill with or suspected of infections with Salmonella, EHEC/STEC, Shigella, Vibrio cholerae, hepatitis A or E viruses or other infectious gastrointestinal diseases, or who excrete the aforementioned bacterial pathogens, must not work in food businesses handling perishable foods and in kitchens according to the Infection Protection Act (IfSG) (see IfSG § 42)
2. The same applies to employees who have inflamed or purulent wounds. Non-infected wounds must be hygienically and properly covered
3. Regular training/instruction of employees regarding required infection control measures
4. Effectiveness control by visual on-site inspections, checks of training documentation and follow-up testing

1. Maintain distance from fields with animal husbandry; keep wild animals away from fields using e.g. fences or nets
2. Water hygiene: do not use contaminated water for irrigation. Irrigation and drainage systems must be suitable. Regular monitoring of microbiological water quality
3. No microbially contaminated fertilizers may be used in crop production
4. Personnel and work hygiene during harvest and downstream steps
5. Remove soil and contamination by washing
6. Effectiveness control by follow-up testing

Use of microbiologically contaminated raw materials or ingredients:

If no reliable inactivation steps are present in the process, the foods produced may be microbiologically contaminated (e.g., raw vegetables or seafood …)

1. Check products at goods receipt for e.g. incoming/transport temperature, shelf life, packaging, deviations or abnormalities
2. The same applies to goods before use in production. In case of doubt, do not use the food and consult supervisors
3. Check microbiological specifications. If necessary, arrange laboratory testing of suspicious products or request results from the supplier
4. Effectiveness control by follow-up testing

1. Review work organization in the facility
   1. Separate work areas, equipment and utensils for raw and processed foods
   2. Separation of "clean" and "unclean" areas and activities
2. Train staff regarding potential faults and improvement measures
3. Effectiveness control by visual on-site inspections and follow-up testing

1. Review processes, production protocols and documentation
2. Inactivation of the viruses from a core temperature of +85 °C for at least 2 minutes
3. Check correctness of processes and temperatures
   1. In general, holding temperatures above +60 °C are required
   2. Rapid cooling: after 3 hours a core temperature of at least +7 °C must be reached (special caution is required for large quantities)
4. Effectiveness control by follow-up testing

1. Require traceability of the cold chain from transport or supplier
2. Check incoming and storage temperatures
3. Monitor refrigeration temperatures and cold chains during processing, transport and sale
4. If overripening (or excessive shelf life) is suspected, carry out appropriate storage tests
5. Effectiveness control by follow-up testing

1. Require traceability of the cold chain from transport or supplier
2. Check incoming and storage temperatures
3. Monitor refrigeration temperatures and cold chains during processing, transport and sale
4. If overripening (or excessive shelf life) is suspected, carry out appropriate storage tests
5. Effectiveness control by follow-up testing

1. Review processes, environmental conditions, production protocols and documentation
2. Effectiveness control by follow-up testing