Successfully reported this slideshow.

Dynamics Of Disease Transmission

17,034 views

Published on

Presentation from Dr. Akhilesh Bhargava

Published in: Health & Medicine, Technology

Dynamics Of Disease Transmission

  1. 1. Dynamics of Disease Transmission Dr. Akhilesh Bhargava MD, DHA, PGDHRM Prof. Community Medicine & Director-SIHFW, Jaipur
  2. 2. E Transmission-prerequisites A H • Agent • Source for agent • Portal of exit from host • Suitable mode of transmission • Portal of entry suitable to agent • Susceptible host 2 Akhilesh Bhargava
  3. 3. Chain of Transmission Mode Eyes Nose Mouth Skin Urinary tract Genital tract Agent 3 Akhilesh Bhargava
  4. 4. Modes of Spread vDirect ü Contact üEnsures certainty üLarger dose, üLess chances of organism dying outside human host ü Airborne ü Droplet (3-5 microns), Distance 1-2 feet ü Droplet Nuclei (< 3 microns) Distance 3-5 feet ü Infected dust ü Transplacental 4 Akhilesh Bhargava
  5. 5. vIndirect v vehicles üWater üFood üMilk üBlood and plasma üOrgans ü Number of case dependent on dose of infection in vehicle ü Cases confined to exposed population ü Large Geographic spread ü Cases start disappearing with vehicle control ü Common source is traceable 5 Akhilesh Bhargava
  6. 6. ü Vectors üMechanical üBiological üCyclo- propogative (change in form &number) e.g. Plague bacilli in Rats üCyclo- developmental (Change in form) e.g. Malarial parasite in mosquito üPropogative (Change in number) e.g. Microfilaria in mosquito 6 Akhilesh Bhargava
  7. 7. Herd Immunity • Resistance of a group to an attack by a disease to which a large proportion of the members of the group are immune • If a large % of population is immune Þ entire population is protected, not just those who are immune 7 Akhilesh Bhargava
  8. 8. Herd Immunity • Why? – If a large % of population is immune then likelihood is small that an infected person will encounter a susceptible person and transmit the infection • More of the encounters will be with other immune people • Important for immunization programs – Do not need 100% coverage immunization rates 8 Akhilesh Bhargava
  9. 9. Herd Immunity Necessary conditions: – Disease agent must be restricted to a single host species within which transmission occurs – Transmission must be relatively direct from one member of the host species to another – Infections must induce solid immunity 9 Akhilesh Bhargava
  10. 10. Herd Immunity • Works when: – Probability of an infected person encountering every other individual in the population (random mixing) is the same • Does NOT work when: – An infected person interacts only with people who are susceptible (no random mixing); likely to transmit the disease to those people 10 Akhilesh Bhargava
  11. 11. How to Prevent & Control Diseases ? • Individual patient level – Counseling – Screening – Treatment • Community level – Surveillance – Targeted measures • Agent • Environment • Host • Route of transmission 11 Akhilesh Bhargava
  12. 12. Basic Control Strategies • Substitution • Treatment • Isolation • Shielding 12 Akhilesh Bhargava
  13. 13. New com pound • Substitution or Process Agent Usually applicable where Physical / Chemical / Nutritional agents are involved 13 Akhilesh Bhargava
  14. 14. Treatment with chem icals / Sterilization • Treatment Antibiotic use Agent 14 Akhilesh Bhargava
  15. 15. • Isolation Agent Disinfection/ Sterilization Universal Precautions Vector control 15 Akhilesh Bhargava
  16. 16. Boosting immune system-Vaccination • Shielding Repellents Housing Behavioral modifications Agent Chemoprophylaxis 16 Akhilesh Bhargava
  17. 17. Prevention & control… Blocking Transmission • Food Hygiene • Water Treatment • Vector Control • Personal Hygiene • Sterilization & Disinfection • Environmental Engineering 17 Akhilesh Bhargava
  18. 18. Prevention & Control: Targeted Strategies Targeted at Reservoir (Human Host) • Early Diagnosis • Notification • Isolation • Surveillance • Quarantine • Disinfection 18 Akhilesh Bhargava
  19. 19. Targeted at Route of transmission – Direct spread • Contact tracing (TB, HIV) • Air quality monitoring • Reducing air microbial density • Avoid overcrowding, improving ventilation • Personal behavior-safe sex, lifestyle advice) • Isolation/quarantine – Indirect spread • Environmental control (proper food handling; water processing) • Safeguarding blood supply • Vector control (pest control) Direct spread through Air borne transmission (Droplet) is difficult to control in general population 19 Akhilesh Bhargava
  20. 20. Targeted at Susceptible Host • Immunization • Chemo- prophylaxis • Physical barriers- »Mosquito nets »Clothing »Housing • Improving Quality of life • Behavioral • Diet/exercise • Smoking/ Alcohol • Hygiene practices 20 Akhilesh Bhargava
  21. 21. Targeted at Agent In the environment Radiation Sterilization Antiseptics Incineration In Human beings Prompt Diagnosis and Treatment of patients with drugs e.g. Antibiotics 21 Akhilesh Bhargava
  22. 22. Targeted at Environment – Early Diagnosis • Lifestyle & behavior (e.g. breastfeeding) – Health services • Policy (notification, contact tracing) • Adequate provision for prompt Diagnosis & Treatment 22 Akhilesh Bhargava
  23. 23. – Legislation • Food hygiene (PFA Act) • Air- – The Air (Prevention & Control of Pollution) Act, 1981 • Water supply – The Water (Prevention & Control of Pollution) Act, 1974 • Sanitation – The Environment protection Act, 1986 – The National Environmental Tribunal Act, 1995 – The Bio-medical waste (Management & Handling Rules), Act, 1998 23 Akhilesh Bhargava

×