| Disease | Agent | Transmission |
| AIDS (acquired immune deficiency syndrome | Virus | Contact of body fluid (semen, blood, vaginal secretions) with that of an infected person. Sexual contact and sharing of unclean paraphernalia for intravenous drugs are the most common means of transmission. |
| Blastomycosis | Fungus | Inhaling contaminated dust |
| Botulism | Bacteria | Consuming contaminated food |
| Chicken pox | Virus | Direct or indirect contact with infected person |
| Common cold | Virus | Direct or indirect contact with infected person |
| Diphtheria | Bacteria | Direct contact with infected person |
| Encephalitis | Virus | Mosquito bite |
| Gonorrhea | Bacteria | Sexual contact |
| Hepatitis | Virus | Direct or indirect contact with infected person |
| Herpes simplex | Virus | Direct contact with infected person |
| Histoplasmosis | Fungus | Inhaling contaminated dust |
| Hookworm | Nematode | Contact with contaminated soil |
| Infectious mononucleosis | Virus | Direct or indirect contact with infected person |
| Influenza | Virus | Direct or indirect contact with infected person |
| Lyme disease | Bacteria | Deer tick bite |
| Malaria | Protozoa | Mosquito bite |
| Measles | Virus | Direct or indirect contact with infected person |
| Mumps | Virus | Direct or indirect contact with infected person |
| Pertussis (whooping cough) | Bacteria | Direct or indirect contact with infected person |
| Poliomyelitis | Virus | Direct contact with infected person |
| Rubella (German measles) | Virus | Direct or indirect contact with infected person |
| Scarlet fever | Bacteria | Direct or indirect contact with infected person |
| Spotted fever | Rickettsia | Tick bite |
| Syphilis | Bacteria | Sexual contact |
| Tapeworm | Nematode | Consuming infected meat or fish |
| Toxoplasmosis | Protozoa | Consuming raw meat; contact with contaminated soil |
| Trichomoniasis | Protozoa | Sexual contact |
| Typhus | Rickettsia | Lice, flea, tick bite |
| Yellow fever | Virus | Mosquito bite |