Infectious Disease Transmission: Routes, Vectors, and Prevention
Infectious agents (viruses, bacteria, fungi, parasites, prions) spread via specific routes from reservoir to susceptible host.
Direct Transmission
- Person-to-person: Respiratory droplets (flu, TB, COVID), direct contact (skin, sexual), vertical (mother→child).
- Animal-to-person: Bites, scratches, contact with tissues/fluids (rabies, toxoplasmosis).
Indirect Transmission
- Fomites: Contaminated surfaces/objects (norovirus, C. difficile, SARS-CoV-2).
- Vehicle-borne: Food (Salmonella), water (cholera), blood products (HIV, HCV), medical devices.
- Airborne: Aerosol nuclei <5 µm (measles, TB, varicella) – travel distances, remain suspended.
Vector-Borne
- Biological: Pathogen replicates in vector (mosquitoes: malaria, dengue; ticks: Lyme; fleas: plague).
- Mechanical: Passive transfer (flies: trachoma, diarrheal pathogens).
Prevention by Route
| Route | Key Interventions |
|---|---|
| Respiratory | Vaccines, masks, ventilation, isolation |
| Sexual | Condoms, PrEP, partner treatment, vaccination (HPV, HepB) |
| Food/Water | Sanitation, hygiene, pasteurization, cooking |
| Vector | Insecticide-treated nets, repellents, environmental management, vaccines (yellow fever, JE) |
| Blood/Body fluids | Screening, universal precautions, needle safety |