Disease common-source outbreaks

As with most viruses, the epidemiology of the NorwaUc-like organism is not well understood. The disease commonly affects children and adults, but it is not often associated with disease in neonates and preschool children. Outbreaks occur throughout the year and have been documented in families, health care systems, cruise ships, and college dormitories. NorwaUc-like viruses are often spread from person to person. Other vectors of transmission include contaminated water supplies, fecal-oral spread, and food-borne outbreaks. Almost any food that has come in contact with contaminated water can serve as a vehicle for an outbreak. A major source of food-borne gastroenteritis is contamination of shellfish beds from raw sewage dumped into the water supply. 

Food borne diseases may effect a large number of persons in a short time from a common source. Previous outbreaks of Salmonellosis connted thousands of affected persons. Two representative examples of these ontbreaks are the following. In the USA in 1985 contamination of pasteurized milk with Salmonella typhimu-rium caused an outbreak of salmonella infection which affected 170,000 people. Another outbreak in China in 1991, contamination of hquid ice-cream with Salmonella enteritidis affected 224,000 people. 

As with travel, international commerce has had a profound effect on health. In recent years, the globalization of the food supply and the development of extensive food distribution networks have increased the risk of foodborne disease outbreaks. In particular, outbreaks associated with fresh produce have caused concern. In 1998, eight restaurant-associated outbreaks of shigellosis caused by a common strain of Shigella sonnet occurred in the United States and Canada. The source, contaminated parsley, was traced to a 1,600-acre farm in Mexico (Naimi et ah, 2003). 

On occasion, the virus spreads beyond the affected individual. The intermediate cycle of yellow fever transmission occurs in humid or semi-humid savannahs of Africa and can produce small-scale epidemics in rural villages. Semi-domestic mosquitoes infect both monkey and human hosts and increased contact between man and infected mosquito leads to disease. This is the most common type of outbreak observed in recent decades in Africa. Urban yellow fever results in large explosive epidemics when travelers from rural areas introduce the virus into areas with high human population density. Domestic mosquitoes, most notably Aedes aegypti, carry the virus from person to person. These outbreaks tend to spread outward from one source to cover a wide area. 

A disease due to the toxicant found in the Lathyrus seed (Lathyrus sativus). The toxin produces an irreversible, gradual weakness, followed by paralysis of both legs (paraplegia). Outbreaks occur in Asia and North Africa mainly during years of poor wheat crops. In these areas, it is common practice to plant Lathyrus with the wheat. If rainfall is adequate, the wheat overgrows the Lathyrus. However, in a year when the rains fail, mainly Lathyrus seed is harvested and it becomes the main dietary energy source and the symptoms... 

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