Communicable Diseases: Epidemiology, Prevention & Control
Communicable Diseases: Epidemiology, Prevention & Control
A comprehensive guide to understanding infectious diseases, their transmission, and control strategies for public health professionals
Core Epidemiology Concepts
Understanding the fundamentals of infectious disease epidemiology
Epidemiological Triad
Agent: Pathogenic organism (virus, bacteria, parasite, fungus)
Host: Human with susceptibility factors
Environment: Conditions facilitating transmission
Modes of Transmission
Airborne: Respiratory droplets (influenza, measles, TB)
Fecal-oral: Contaminated food/water
Vector-borne: Insects (malaria, dengue)
Contact: Direct person-to-person
Disease Patterns
Endemic: Constant presence in population
Epidemic: Sudden increase above baseline
Pandemic: Widespread across multiple countries
Surveillance & Monitoring
Active Surveillance: Regular contact with health facilities
Passive Surveillance: Report-based system
Outbreak Investigation: Identifying source and contacts
Communicable Diseases Overview
Details on epidemiology, transmission, and control measures
Measles
Agent
Measles virus (paramyxovirus)
Transmission
Airborne respiratory droplets
Incubation
7-21 days (average 10 days)
Rubella
Agent
Rubella virus (togavirus)
Transmission
Respiratory droplets
Incubation
14-21 days
Mumps
Agent
Mumps virus (paramyxovirus)
Transmission
Respiratory droplets, saliva
Incubation
16-18 days (range 12-25)
Influenza
Agent
Influenza A, B, C viruses
Transmission
Respiratory droplets, aerosols
Incubation
1-4 days
Viral Hepatitis
Agent
Hepatitis A, B, C, D, E viruses
Transmission
Fecal-oral (A, E); Bloodborne (B, C, D)
Incubation
15-50 days (varies by type)
Japanese Encephalitis
Agent
Japanese encephalitis virus (flavivirus)
Transmission
Mosquito-borne (Culex species)
Incubation
5-15 days
Acute Respiratory Tract Infection
Agent
Multiple viruses and bacteria
Transmission
Respiratory droplets, aerosols
Incubation
1-5 days (varies)
Diphtheria
Agent
Corynebacterium diphtheriae
Transmission
Respiratory droplets
Incubation
2-5 days
Whooping Cough (Pertussis)
Agent
Bordetella pertussis
Transmission
Respiratory droplets
Incubation
7-14 days
Tuberculosis (TB)
Agent
Mycobacterium tuberculosis
Transmission
Airborne droplet nuclei
Incubation
3-8 weeks (can be prolonged)
Typhoid Fever
Agent
Salmonella typhi
Transmission
Fecal-oral (contaminated food/water)
Incubation
6-30 days (average 10-14)
Tetanus
Agent
Clostridium tetani
Transmission
Wound contamination (non-communicable)
Incubation
3-21 days (average 7-10)
Intestinal Worms
Agent
Roundworms, hookworms, tapeworms
Transmission
Contaminated food/water, soil
Incubation
Weeks to months
Food Poisoning
Agent
Bacteria, viruses, toxins, parasites
Transmission
Contaminated food/water
Incubation
Hours to days
Acute Diarrhoeal Diseases
Agent
Viruses, bacteria, parasites, toxins
Transmission
Fecal-oral route
Incubation
1-7 days
Filaria (Lymphatic Filariasis)
Agent
Wuchereria bancrofti, Brugia malayi
Transmission
Mosquito-borne
Incubation
4-6 months
Leishmaniasis
Agent
Leishmania species
Transmission
Sandfly vector
Incubation
Weeks to months
Malaria
Agent
Plasmodium species (P. falciparum, P. vivax, etc.)
Transmission
Anopheles mosquito-borne
Incubation
7-30 days (varies by species)
Rabies
Agent
Rabies virus (rhabdovirus)
Transmission
Animal bite/saliva (non-communicable person-to-person)
Incubation
1-3 months (variable)
Trachoma
Agent
Chlamydia trachomatis (serovars A-C)
Transmission
Contact with eye/nasal secretions
Incubation
7-14 days
Leprosy (Hansen's Disease)
Agent
Mycobacterium leprae
Transmission
Respiratory droplets (untreated)
Incubation
2-5+ years
STI & HIV/AIDS
Agent
HIV virus, other STI pathogens
Transmission
Sexual contact, blood exposure, mother-to-child
Incubation
Window period: 18-45 days
Prevention & Control Strategies
Evidence-based approaches to disease prevention at individual and population levels
Primary Prevention
Immunization: Vaccines for measles, diphtheria, pertussis, tetanus, influenza, hepatitis, JE, rubella, mumps
Health Education: Safe food/water practices, hygiene promotion
Environmental Health: Sanitation, water quality management
Secondary Prevention
Early Detection: Surveillance and screening programs
Case Management: Rapid diagnosis and treatment
Contact Tracing: Identify and monitor exposed individuals
Isolation/Quarantine: Prevent transmission to others
Tertiary Prevention
Rehabilitation: Post-TB treatment monitoring
Disability Management: Leprosy complications, rabies prevention
Palliative Care: HIV/AIDS support
Complication Prevention: Micronutrient supplementation for measles
Population-Level Control
Vector Control: Insecticide-treated nets (malaria, dengue), environmental management
Food Safety: Inspection and hygiene standards
Outbreak Response: Epidemiological investigation and containment
Case Reporting: Surveillance system data submission