Principles of Epidemiology and Microbiology
Lesson
1: Introduction to Disease Transmission and Epidemiology
1-7
1-7. SOURCES OF DISEASE (RESERVOIRS)
The source of disease may be a case, a carrier, or an animal.
a. Case. A person who is actually ill with a disease is called a case. A case is a common source of infection.
b. Carrier. A person who harbors disease organisms but who is not ill is called a carrier. This person can spread the germs in the same manner as the case. Actually, he is more dangerous because he may not know that he is harboring the infectious germs.
c. Animal. An animal can actually be ill with disease or it can harbor the organisms, spreading it to humans in either instance. The term animal means any member of the animal kingdom, thus including insects as well as mammals.
