Briefly describe (a) Infectious agents; (b) Means of transmission of disease.

(a) An infectious agent is something that infiltrates another living thing, like you. When an infectious agent hitches a ride, you have officially become an infected host. There are four main classes of infectious agents: bacteria, viruses, fungi, and parasites.

(b) Infectious diseases are transmitted from person to person by direct or indirect contact. Certain types of viruses, bacteria, parasites, and fungi can all cause infectious disease. Malaria, measles, and respiratory illnesses are examples of infectious diseases.