How these diseases spread depends on the specific disease or infectious agent. Some ways in which communicable diseases spread are:
1. physical contact with an infected person, such as through touch (staphylococcus), sexual intercourse (gonorrhea, HIV), fecal/oral transmission (hepatitis A), or droplets (influenza, TB)
2. contact with a contaminated surface or object (Norwalk virus), food (salmonella, E. coli), blood (HIV, hepatitis B), or water (cholera);
3. bites from insects or animals capable of transmitting the disease (mosquito: malaria and yellow fever; flea: plague); and
4. travel through the air, such as tuberculosis or measles.