Docs with no common sense

Is parasite illnesses contageous or not? If a person from cuba or haiti or africa ir mexico works in a kitchen in a restaurantsay as a cook. and has a parasite disease how many people can that 1 person infect? thousands? And how many other lives can 1 person effect? Where has common sense gone in the medical profession, them telling us that we cant have parasites because we live in the USA when we have a melting pot of all ethnics in the USA. This is a complete lack of common sense and could cause a plague of illnesses from parasites. How is this logic even tollerated? How many lives have been destroyed by this ignorance? Is it contageous or not??? Regardless of your skin color, parasites dont care where your from or your ethinticity! IS IT CONTAGEOUS BY LESS FORTUNATE PEOPLE IN OUR COUNTRY WHO COOK AND HANDLE OUR FOOD OR NOT?