Communicable Disease Control
Core concepts
Understand the epidemiologic triad (agent, host, environment), modes of transmission (direct, droplet, airborne, vector-borne, vehicle-borne), and the chain of infection. Master R0, epidemic curves (common-source vs propagated), and outbreak investigation. Know vaccine types (live attenuated, inactivated, toxoid, subunit, mRNA), cold chain, and immunisation schedules. Be familiar with tuberculosis, HIV, malaria, hepatitis, and emerging infections, plus principles of antimicrobial resistance and infection prevention and control. Understand surveillance types (passive, active, sentinel) and notification.
Traps
- Confusing airborne (e.g., TB, measles) with droplet (e.g., influenza) transmission.
- Assuming live vaccines are safe in immunocompromised patients-they are contraindicated.
- Misreading an epidemic curve: a single sharp peak suggests a common-source exposure.
- Forgetting that R0 is a property of the pathogen–population interaction, not fixed.
Worked example / rule of thumb
A point-source outbreak shows cases rising rapidly and falling after the exposure ends, with a single peak within one incubation period. A propagated outbreak shows successive peaks one incubation period apart. Rule of thumb: look at the shape of the epidemic curve and the timing of exposures to distinguish common-source from person-to-person spread.