Foodborne Viruses

Viral Hepatitis A

Hepatitis A (previously called infectious hepatitis) is caused by the Hepatitis A virus. The onset of this illness is often abrupt with fever, malaise, anorexia and abdominal discomfort being the main symptoms. However, many adults and most children may be infected (and infectious) but have no or very mild symptoms. These symptoms may be followed by jaundice which is the yellowing of the skin and the whites of the eyes. The incubation period (the time from exposure to symptoms) is normally about 4 weeks but can be anywhere from 2 to 7 weeks depending on the dose of the virus eaten.

People with symptoms may be ill for as little as 1 ¬ 2 weeks, but most people do not feel fully recovered for quite a few weeks. In some rare cases, people are severely ill for several months and liver failure and death occasionally occur.

Because of good sanitation practices in countries like Canada, exposure to the virus does not usually occur until later in life. Children can be infected but this is less common and they are unlikely to show any symptoms.

How Is Hepatitis A Spread?

Other people are the only source of the hepatitis virus. The virus is found in faeces in high numbers a week or two before symptoms become obvious. Therefore, it is possible to unknowingly spread the virus to other people through lapses in proper personal hygiene (hand washing). Outbreaks have been associated with contaminated water; food contaminated by infected foodhandlers, including sandwiches and salads which are not cooked or are handled after cooking; and raw or undercooked shellfish which were grown in sewage¬polluted waters.

Disease transmission is also frequent in day care centres, particularly where there are children in diapers. In such cases, it is often older family members of children in day care or staff in the day care who are affected, while the children themselves have no symptoms. Household contacts, and people sharing things with other infected individuals, are also at increased risk of infection.

How Do You Prevent Hepatitis A?

* Thoroughly cook all seafood (oysters, clams and other shellfish) to a temperature of 85 ¬900C for 4 minutes before eating.

* Avoid recontamination of cooked food by placing them on clean surfaces which were not previously used for the preparation of other foods.

* Educate foodhandlers and other persons preparing food about good sanitation and personal hygiene. In particular, emphasis

* should be on proper handwashing before, during and after food preparation, and the sanitary disposal of faeces.

* Foodhandlers who are acutely ill should stay off work for at least one week after symptoms develop.

* Never order or accept raw shellfish in an eating establishment.

* Buy or use shellfish obtained from approved sources only.

How Do You Control Hepatitis A?

* See your personal physician for diagnosis and treatment.

* If a Hepatitis A outbreak is suspected in your community, an in¬depth investigation will be conducted.

* If you have been infected, you should be prepared to answer detailed questions, and to submit faecal or blood samples to health authorities.

* Persons who have been in contact with a case of hepatitis may be protected with immune globulin (IG or gamma globulin.) Your doctor or health unit will advise if IG is appropriate for you.

viral infections

The most important agents of these diseases are:

Mouth and foot disease virus: is present in all kind of tissues of cattle and swine. Hepatitis A - virus

Hepatitis E - virus

Influenza viruses: They can be divided in three types: A, B and C.

Especially the type A undergoes genetic variation. Thats the reason why often new strains of influenza arise. These strains are called serotypes because they can be distinguished by serological agglutination tests. Influenza-A-virus: is found in lung of swine. It is the most common type of influenza outbreaks in humans.

Norovirus

Norovirus should replace the designation "flu-like", "Norwalk-like","Norwalk- and Norwalklike viruses (Caliciviruses) ", "bug".

Norwalk- and Norwalklike gastroenteritis virus are leading causes of foodborn diseases:Norwalk virus is part of a family which is not well defined It causes stomach and intestinal illness. It was first identified in 1972 in the city of Norwalk ( Ohio. The group if these viruses are recently called Noroviruses. The are from the genus Norovirus, family Caliciviridae. They are single stranded RNA, nonenveloped. They spread by person-to-person contact from the stool of infected persons and its symptoms are vomiting and diarrhoea.Special care is needed to avoid spreading of the disease such as:

Avoid food or water which has been contaminated by stool from infected persons, raw shellfish, oysters, clams, ice, eggs, salads and other food contaminated by sick food handlers or water which has been contaminated by sewage of cities or disposals of boats.

Incubation is 1 to 2 days. Illness is not severe, but rehydration may be necessary. Recovery in 2 to 3 days. People with the virus are contagious skin to skin for 3 days after symptoms have disappeared. The stool remains infectious for 2 to 3 weeks after symptoms are gone. Strict handwasching and use of disinfectants are very important to avoid spreading of the virus.

People can be reinfected and have the disease several times in life because there are many strains and a strong mutagenic activity.

Food should be served in restaurants authorised persons only instead of self-serving service.

Hotels should carefully clean bed clothes and pillow cases. Refrigerators and icemachines should be thawed and cleaned periodically. As disinfectant chlorine water solution should be used.

Viral gastroenteritis outbreaks caused by caliciviruses have been associated with eating contaminated shellfish, particularly oysters (Crassostrea virginica), implicating sewage from oyster harvesting vessels as the probable cause of contaminated oysters.

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