There are four main types of air pollution sources: mobile sources â such as cars, buses, planes, trucks, and trains stationary sources â such as power plants, oil refineries, industrial facilities, and factories
Incubation Period: Average 9-10 days. Period of Communicability: Highly communicable in the early phase and at the beginning of the paroxysmal cough stage (first 2 weeks). The child is no longer contagious after 5 days of treatment.
The Contagious Period. A person is contagious during the hepatitis B incubation period. A person who is infected with the virus begins to be contagious early in the incubation period. About one-half of people remain contagious for up to two months after symptoms begin. The remainder of people who do not develop chronic hepatitis B will remain contagious for up to 15 weeks after symptoms begin.