Accordingto Institute of Food Science and Technology (2010), food was first recognizedas a vehicle for viruses in an outbreak of raw-milk associated poliomyelitis in1914 followed with an outbreak in a primary school in Norwalk, Ohio in 1918where Norwalk virus was identified as the cause of infection in both childrenand adults. In the middle of 1950s, shellfish was identified as thetransmission route in Sweden and then in the United States. The introduction ofmolecular methods in 1990s led the identification of viruses as the leadingcause of human gastroenteritis in developed countries. There are many differentviruses can cause gastroenteritis including norovirus, adenoviruses,sapoviruses and astroviruses and the symptoms are similarly to gastroenteritiscaused by bacteria and parasites. Koopman,M. (2012) described foodborne transmission is one mode of transmission for manyviruses associated with disease ranging from mild diarrhea to severeneurological symptoms.
Foodborne viruses transmission can occur by faecal-oralroute through contamination of food by food handlers during food production, bycontamination of food during the production processes or by consumption ofproducts of animal origin harboring a zoonotic virus. The viruses will infecttheir hosts after ingestion, followed by invasion of cells in the epitheliallining of the gut and replicate in the same site or in another place in the body. The most frequently identifiedfoodborne viruses through those transmission routes are norovirus, Hepatitis Avirus, severe acute respiratory syndrome (SARS)-associated coronavirus, Nipahvirus and Hepatitis E virus.
Accordingto IFST (2010), foods which are associated with foodborne viruses outbreaksincluding:a. Molluscanshellfish including oysters, cockles, musselsb. Vegetablesc. Fruitsd. Drinking watere. Fruit juicesf. Milkand milk productsg. Undercooked wildboar or deer meath.
Pig liver sausagei. Porkliversj. Saladdressing and cake icings Incontrast with foodborne bacterial infections which has established microbiologicalcontrol criteria as indicators for food contamination, control criteria forfoodborne viruses is unavailable to protect against foodborne virus infection.
According to Diane et al., (2010), the fundamental properties of foodborneviruses should be understand in order to establish preventive program and to designappropriate control measures. There are few challenges in dealing withfoodborne viruses as described by Diane et al.,(2010) and IFST (2010): a. There is nosystematic surveillance for foodborne viral diseaseMost countries have somelevel of reporting of foodborne illness outbreaks but few of these systemsinclude viral foodborne illness. Although case based surveillance is establishedfor hepatitis A and enterovirus, it does not focus on detecting foodborne virustransmission as a source of infection resulting insufficient statistics onfoodborne viral diseases or under-reporting.
b. Detection andisolation of food or waterborne viruses is limited by : i. thenon-routine nature of testing for the viruses in foods as the viruses needliving host or tissue to replicate ii. longincubation of some viruses such as Hepatitis A iii. difficultyor inability to culture in laboratory cell cultures iv.
thelow level of virus particles in a contaminated food v. techniquespreviously available are not suitable for routine application with low recoveryrates c. Unnoticedinfections of foodborne viruses due to symptoms which are relatively mild.
Forexample infections of Noroviruses which are recognized as one of the commoncauses of gastroenteritis at the community level. As the symptoms are mild,infections go unnoticed except during major outbreaks especially in health careinstitutions such as nursing homes and hospitals.d. Application ofappropriate control measures. For example, freezing will not affect infectivityof viruses, in fact it may help to preserve the viruses.
Many fruits andvegetables are sold unwashed or with little processing.