Scientists discuss ways to control foodborne viruses

Experts have assessed prevention and intervention methods to tackle foodborne viruses in different products.

In February, the Joint FAO/WHO Expert Meeting on Microbiological Risk Assessment (JEMRA) on viruses in foods took place in Geneva, Switzerland, after a related request by the Codex Committee on Food Hygiene in 2022. The committee is meeting in Kenya this week.

The event focused on prevention and intervention measures. The findings have been summarized, and the full report will be available later.

The first part of the meeting in September 2023 in Rome, Italy, covered food attribution, analytical methods, and indicators. The virus-commodity combinations of highest priority were human norovirus and hepatitis A virus in shellfish, fresh and frozen produce, prepared and ready-to-eat (RTE) foods, and hepatitis E virus in pork and wild game.

At the second meeting, experts reviewed the scientific literature published since the 2008 JEMRA report on foodborne viruses and control measures to protect the supply chain from contamination.

Since the 2008 report, awareness of the public health importance of these virus-commodity combinations has increased, resulting in changes to some food supply chain management strategies, said scientists.

Shellfish and produce
Human fecal matter and vomit from infected individuals are the primary sources of contamination for norovirus and hepatitis A. The main contamination routes are fecally-impacted waters, food handlers carrying viruses, and surfaces. Microscopic amounts of the contaminants are enough to cause illnesses in humans. The zoonotic hepatitis E virus is in the meat, organ tissues, and excretions of infected swine and some game animals.

Experts say that prevention remains vital to control foodborne viruses because they are environmentally persistent and resistant to many treatments commonly used to inactivate pathogens.

For shellfish, sanitary surveys are increasingly used to evaluate human fecal pollution status in growing areas and can determine conditions in which harvesting can occur safely. Using more effective wastewater treatment can reduce viral loads in effluent but requires infrastructure investment. Climate change is expected to result in heavier rainfall in some locations, which may increase the likelihood of sewage overflows or runoff. Contaminated products are discarded or diverted to processing such as depuration or heat treatment.

Fresh and frozen produce are usually contaminated pre-harvest by sewage sludge, human fecally-impacted source waters, and infected food handlers. Frozen produce, especially berries, dominate outbreaks, aided by the fact that freezing preserves virus infectivity and results in globally distributed products with a long shelf-life. Production-related interventions should focus on the water source, location, method, and application timing. According to experts, emerging water treatments, such as ozone, ultraviolet, and ultrafiltration, show potential but require infrastructure investment.

RTE food and pork meat
Prepared and infected food handlers usually contaminate RTE foods. Prevention focuses on the exclusion of infected workers, surface disinfection, and attention to personal hygiene, including handwashing. Policies exist, and handwashing is promoted, but compliance is often poor.

Hepatitis E exposure can occur by consuming raw or inadequately cooked meats and direct contact with infected animals on farms or slaughterhouses. Studies suggest control measures should focus on preventing animal infection at the pre-harvest phase via biosecurity measures and disinfection and post-harvest interventions like preventing cross-contamination and virus inactivation by heat.

Experts said one issue was the limited ability to routinely cultivate wild-type foodborne viruses in the lab, which complicates the chance to validate interventions, compare studies, and interpret monitoring data.

They added that early identification of contamination hotspots may be a useful control tool, the usefulness of indicator organisms in predicting virus occurrence and infectivity could be better understood, and novel interventions should be validated using the relevant viruses before wide application in real-world situations.

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