NEET PG High-Yield: Classification of Transmission
Infectious agents utilize various modes to spread from a reservoir to a host. Understanding this classification is key to implementing effective infection control protocols.
| Mode | Description | Examples |
|---|---|---|
| Direct | Direct contact, droplet spread, contact with soil/skin. | HIV, STIs, Rabies, COVID-19 (Droplet). |
| Indirect: Vehicle | Contaminated materials (fomites), water, food, and biological products. | Cholera (Water), Hep A (Food). |
| Indirect: Vector | Mechanical (physical transport) or Biological (multiplication). | Malaria (Mosquito – Bio), Housefly (Mech). |
| Indirect: Airborne | Suspension in dust or aerosolized particles (>5 µm) travels long distances. | Tuberculosis, Measles, Varicella. |
High-Yield NEET PG Pearls:
- Droplet vs. Airborne: Droplets are larger (>5 µm) and fall quickly to the ground (within 1 meter). Airborne particles are smaller and remain suspended for hours.
- Vehicle vs. Vector: A vehicle is inanimate (water, food, surface). A vector is a living (insect, animal).
- Mechanical Vector: The pathogen does not multiply in the vector (e.g., housefly carrying Shigella on its legs).
- Biological Vector: The pathogen must undergo multiplication or a cycle of development in the vector (e.g., Plasmodium in Anopheles).