Foodborne viruses - what they cause, how they get into food, and what we can do about it
In recent years there has been an ever increasing awareness of the threat of foodborne viruses in the global food supply chain. In 2011, the US Centers for Disease Control and Prevention (CDC) estimated that each year roughly 48 million US citizens gets sick, 128 000 are hospitalized, and 3000 die from foodborne diseases. They report that almost 60% of domestically acquired foodborne illnesses were caused by norovirus, as compared to the other four of the top 5 pathogens of concern. This resulted in an estimated 5.5 million illnesses, of which nearly 15,000 infections required hospitalization and 149 died (http://www.cdc.gov/foodborneburden/2011-foodborne-estimates.html).
In the EU, data gathered in 2009 shows that enteric viruses were responsible for more than 1,000 outbreaks (19% of the total of all outbreaks), affecting nearly 9,000 people, with numbers on the increase since 2007 (EFSA 2011).
In the UK, the Food Standards Agency's (FSA) Strategic Plan for 2015-2020 has, as one of its main objectives, "to protect public health from risks which may arise in connection with the consumption of food (including risks caused by the way in which it is produced or supplied) and otherwise to protect the interest of consumers in relation to food. This would include the reduction of foodborne disease to ensure that food is safe." The Strategic plan has resulted in the FSA's commitment to gaining a better knowledge of the threat posed by foodborne viruses, through scientific projects aiming to identify the scale of the threat to the UK population and by identifying potential methods to help the food industry adopt appropriate control measures. The issues surrounding foodborne viruses were considered so serious that, in February 2016, the FSA alongside the European Food Safety Authority (EFSA) held an international workshop on foodborne viruses to identify key research priorities to help the industry, scientists and regulators to understand and manage the risk to consumers and thereby protect public health.
This white paper looks at the viruses concerned, how they get into food, and how we can detect and control them.
The Viruses: Norovirus, Hepatitis A and Hepatitis E
There are three viruses of primary concern in food safety: Norovirus, Hepatitis A and Hepatitis E. Noroviruses (NoV) are transmitted via the faecal-oral route, and are highly contagious, with the infectious dose thought to be approximately 18 virus particles (Teunis et al., 2008). Noroviruses are non-enveloped, about 27 to 32 nm in size, and are single-stranded RNA enclosed in a capsid (outer protein shell), and belong to the Caliciviridae family. The incubation period of NoV in humans is around 12-72 hours, often with a rapid onset of symptoms which usually appear 20-30 hours after infection. Symptoms are generally mild, but include projectile vomiting and/or one to several days of diarrhoea; therefore dehydration is the biggest issue related to NoV infection.