The Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) have collaborated on a new report that ranks the most common viral foodborne illnesses.

The report from the Joint Expert Meeting on Microbiological Risk Assessment (JEMRA), published in December 2024, found that norovirus is the leading cause of foodborne illness.

According to the report, they came to this conclusion after conducting a “review of viruses known to be associated with foodborne illness in humans.

The frequency of illness and clinical severity, as well as virus-food combinations, are ranked in the context of foodborne illness,” Food&Wine reports.

The report took a semi-quantitative approach, meaning that it took into account specific numbers as well as the “expert knowledge” of the report’s authors.

As for the foods most likely to be linked to norovirus, they found that it is usually ready-to-eat foods, frozen berries, and shellfish.

The Centers for Disease Control and Prevention (CDC) explains that the most common symptoms of norovirus are diarrhea, vomiting, nausea, and abdominal pain. However, symptoms such as fever, headache, and body aches may also be present.

Norovirus is estimated to cause 125 million cases of foodborne illness and 35,000 deaths worldwide each year, the authors of the joint report added.

According to the CDC, it causes 2,500 outbreaks in the United States alone, accounting for 58% of foodborne illnesses in the country.

Norovirus is highly contagious, and outbreaks of the virus have been linked to foods with low levels of contamination. Viral contamination can occur throughout the food chain.

Severe outcomes, including hospitalization and death, mainly affect children under five, the elderly and people with weakened immune systems who can shed the virus for a long time.”

Along with norovirus, hepatitis A, the second most common viral disease, is also on the unpopular list. According to the report, it causes 14 million cases of foodborne illness and 28,000 deaths worldwide each year.

There are significant regional differences in the proportion of hepatitis A cases attributed to food, due to endemic prevalence and vaccine use, it added.

International food trade plays an important role in transmitting the virus to susceptible populations. Greater compliance with international standards, such as good agricultural and hygiene practices, is likely to reduce global transmission.

The report added that transmission is most commonly associated with shellfish, frozen berries and ready-to-eat foods.

And in third place is the hepatitis E virus, which the report says is “unique among foodborne viruses” because it is “a zoonotic pathogen with many asymptomatic animal carriers, particularly pigs.”

It noted that there is no global estimate of cases attributed to food, but that countries that have investigated its spread “have found that their previous estimates are too low.”

Hepatitis E, the report added, can cause severe illness, especially in people with pre-existing medical conditions, and can lead to cirrhosis of the liver and neurological damage.

Undercooked pork products, including liver or raw sausage containing liver or blood, as well as liver pâté, are the main foods contaminated with the hepatitis E virus, it warns.

Most common viral foodborne diseases

Norovirus: 125 million cases and 35,000 deaths per year
Hepatitis A: 14 million cases and 28,000 deaths per year
Hepatitis E: 3.3 million cases and 44,000 deaths per year
However, a number of other viruses, including astrovirus, sapovirus, enterovirus, enteric adenovirus and rotavirus, may actually outnumber them.

The team said there were “insufficient data to rank the foods that could be contaminated” with these viruses.

While all this is alarming, the authors also said that improved surveillance and better reporting of cases of these foodborne illnesses could help control or prevent their spread.

The expert committee recommends that member states consider developing training capacities and adopting these methods for detecting viruses in food and the environment, it concluded.

This approach has the potential to improve knowledge about food attribution, support risk analysis, and reduce the number of foodborne viral diseases worldwide.

Appropriate global action will help mitigate the expected increase in the risk of these viral diseases due to population growth, the climate crisis, and the globalization of food supply chains. Ultimately, better training and detection could save millions of lives worldwide.