Incubation period refers to the time from exposure to a pathogen until when the first symptoms appear in the host. Incubation period depends on the amount of exposure to the pathogenic agent, the host's immune response as well as how quickly the germ multiplies. Examples of varying incubation periods include the following--chicken pox is about 2 weeks, cholera is between 1-3 days, influenza is between 1-3 days, common cold is between 1-3 days. HIV can incubate between 2 and 3 months or longer. Therefore, it is very possible, depending on the disease pathogen to become ill overnight.