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.
A person is contagious during the hepatitis D incubation period. Someone who is infected with hepatitis D begins to be contagious early in the incubation period.The point at which a person is thought to be most contagious is right before symptoms begin. If a person develops chronic hepatitis D, he or she remains contagious indefinitely.* For hepatitis B, the incubation period is between 4 and 20 weeks.  * For hepatitis C, it's estimated that the incubation period is 2 to 26 weeks.