| Disease | How Agent Leaves the Body | How Organisms May Be Transmitted | Method of Entry into the Body |
|---|
| Acquired immunodeficiency syndrome (AIDS) | Blood, semen, or other body fluids, including breast milk | Sexual contact | Reproductive tract |
| Contact with blood or mucous membranes or contaminated syringes | Contact with blood |
| Placental transmission | Placental transmission |
| Breastfeeding |
| Cholera | Feces | Water or food contaminated with feces | Mouth to intestine |
| Diphtheria | Sputum and discharges from nose and throat | Droplet infection from patient coughing | Through mouth or nose to throat |
| Skin lesions (rare) |
| Ebola virus | In body fluids such as blood, saliva, sweat, or urine | By direct contact with blood, body fluids, or skin | Through contacted tissue |
| Gonococcal disease | Discharges from infected mucous membranes | Sexual activity | Reproductive tract or any mucous membrane |
| Hepatitis A, viral | Feces | Food or water contaminated with feces | Mouth to intestine |
| Hepatitis B, viral and hepatitis D | Blood and serum-derived fluids, including semen and vaginal fluids | Contact with blood and body fluids | Exposure to body fluids including during sexual activity, injection drug abuse, or surgery |
| Contact with blood |
| Hepatitis C | Blood and other body fluids | Parenteral drug use | Infected blood |
| Laboratory exposure to blood | Contaminated needles |
| Health care workers exposed to blood, e.g., dentists and their assistants and clinical and laboratory staff | Cuts; mucosal exposures |
| Hookworm | Feces | Cutaneous contact with soil polluted with feces | Larvae enter through skin (esp. of feet), migrate through the body, and settle in small intestine |
| Eggs in feces hatch in sand y soil |
| Influenza | As in pneumonia | Respiratory droplets or objects contaminated with discharges | As in pneumonia |
| Leprosy | Cutaneous or mucosal lesions that contain bacilli | Cutaneous contact or nasal discharges of untreated patients | Nose or broken skin |
| Respiratory droplets |
| Measles (rubeola) | Discharges from nose and throat | Respiratory droplets | Through mouth and nose |
| Meningitis, meningococcal | Discharges from nose and throat | Respiratory droplets | Mouth and nose |
| Mumps | Discharges from infected gland s and mouth | Respiratory droplets and saliva | Mouth and nose |
| Ophthalmia neonatorum (gonococcal infection of eyes of newborn) | Vaginal secretions of infected mother | Contact with infected areas of vagina of infected mother during birth | Directly on conjunctivae |
| Pertussis | Discharges from respiratory tract | Respiratory droplets | Mouth and nose |
| Pneumonia | Sputum and discharges from nose and throat | Respiratory droplets | Through mouth and nose to lungs |
| Poliomyelitis | Discharges from nose and throat and via feces | Respiratory droplets; contaminated water | Through mouth and nose |
| Rubella | Discharges from nose and throat | Respiratory droplets | Through mouth and nose |
| Streptococcal pharyngitis | Discharges from nose and throat | Respiratory droplets | Through mouth and nose |
| Syphilis | Lesions | Sexual intercourse; contact with skin or mucous membrane lesions | Directly into blood and tissues through breaks in skin or membrane |
| Blood | Contaminated needles and syringes | Contaminated needles and syringes |
| Transfer through placenta to fetus |
| Tuberculosis, bovine | Hand s, towels, hand kerchiefs | Milk from infected cow | Mouth to intestine |
| Tuberculosis, human | Sputum | Droplet infection from person coughing with mouth uncovered | Through nose to lungs or intestines |
| Typhoid fever | Feces and urine | Food or water contaminated with feces or urine from patients | Through mouth via infected food or water and thence to intestinal tract |