Germ Warfare: Viruses

Dear Dr. B: What is a virus? What are the common viruses which cause illnesses in humans?

Answer: A virus is a minute organism that consists of a core of nucleic acid surrounded by protein. Viruses can grow and reproduce only inside living cells such as bacteria, plants and animals. They are composed of RNA or DNA. Viruses are very small. A special kind of microscope is required to see them.

There are many, perhaps hundreds of different viruses causing all kinds of diseases in animals and plants. Some examples of common human diseases caused by viruses are: AIDS, measles, mumps, smallpox, yellow fever, rabies, poliomyelitis, influenza, the common cold, hepatitis and certain types of cancers. Viruses also cause gastroenteritis.

In the last few months many institutions have fallen victim to viral gastroenteritis, also known as “stomach flu,” although influenza virus has nothing to do with gastroenteritis. Getting a flu shot will not prevent viral gastroenteritis. Many different viruses can cause gastroenteritis, including rotaviruses, adenoviruses, caliciviruses, astroviruses, Norwalk virus and a group of Norwalk-like viruses, now known as noroviruses.

The main symptoms of viral gastroenteritis are watery diarrhea and vomiting. The affected person may also have headache, fever and abdominal cramps (stomachache). In general, the symptoms begin one to two days following infection with a virus that causes gastroenteritis and may last for one to 10 days, depending on which virus causes the illness.

Normally the prognosis is good. Most people recover completely without any long-term effects. But in children and old patients the disease can be fatal if fluid and electrolyte balance of the body is not maintained.

Viral gastroenteritis is contagious. The virus spreads through close contact with infected persons by sharing food and water. Food may be contaminated by people who cook or handle food who have viral gastroenteritis, especially if they do not wash their hands regularly after using the bathroom or changing diapers.

Viral gastroenteritis can affect people in all parts of the world. Some viruses have seasonal activity and occur during cooler months of October to April. Quite often the outbreaks occur in institutional settings such as schools, hospitals and nursing homes and group settings such as cruise ships. Transmission of Norwalk virus is through the fecal-oral route.

Studies have shown water is the most common source of outbreaks. Shellfish and salad ingredients are the foods most often implicated in Norwalk outbreaks. Ingestion of raw or insufficiently steamed clams and oysters poses a high risk for infection with Norwalk virus. Rotavirus and the Norwalk family of viruses are the leading causes of viral gastroenteritis.

Wash your hands, clean and cook your food well and maintain good hygiene. That’s the best way to prevent gastroenteritis. If you like to eat out then pick your restaurants carefully.

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