Class test on Infectious Disease Epidemiology

1. Class test on Infectious Disease Epidemiology Dr. Pracheth R. MD, DNB, PGDipPHSM

3. Modes of transmission Direct contact: • Direct contact: STD, leprosy • Droplet infection • Soil • Innocculation into skin/mucosa • Transplacental/vertical

4. Indirect (Flies, fingers, fomites, food, fluid) Vehicle borne: • Water, food, milk and milk products • Diarrhoea, cholera, typhoid

7. Vector borne • Arthropod/living carrier: transports agent- susceptible individual • Methods of transmission Mechanical: flies Biological: Replication/development /both in vector

8. Continued…. • Propagative: multiplies, no change in form. Plague bacilli in rats • Cyclo-propagative: form, number: malaria parasites • Cyclo-developmental: only development, no multiplication. Microfilaria in mosquito

9. Airborne • Droplet nuclei: • Tiny particles; dried residues of droplets • 1-10 microns • TB, influenza, chicken pox • Dusts: • Larger droplets: settle dusts • Pneumonia, tuberculosis

10. Fomite borne • Inanimate objects other than water, food • Soiled clothes, towels, linen, cups • Diphtheria, typhoid, dysentry

11. Unclean hands and fingers • Staphylococcal, streptococcal • Lack of personal hygiene

13. Successful parasitism • Portal of entry • Site of election • Portal of exit: • Dead end infection • Survival in external environment

14. Cold chain • System- storage and transport vaccines – recommended temperature from manufacture to vaccination site • Polio- heat sensitive: -20 degree C • Freezer: Polio, measles • Cold part, not freeze: typhoid, tetanus, DPT, DT, BCG

15. Cold chain equipment • Walk in cold rooms: • Regional level • Store vaccines- 3 months • 4-5 districts

16. Walk-in cold rooms (WIC)

17. Contd… • Deep freezers (300 l) and ILR (320 l) • All districts, WIC locations • Make ice packs • OPV, measles • Small deep freezer and ILR (140 l): • PHCs • Deep freezers: make ice packs used in cold box, vaccine carriers- transport vaccines.

18. Deep freezers

19. Ice-lined refrigerators (ILR)

20. Dial thermometer

21. Contd.. • All vaccines in PHC: stored in ILR • TT, DT, DPT: basket in ILR • Not kept on floor: freeze and spoil • Dial thermometer: temp , twice a day • Defrosting: vaccines to cold boxes containing ice packs • Equipment/ electric failure: ice boxes and then alternative vaccine storage

22. Dos of ILR • Keep cool room, away direct sunlight • ILR- levelled • Voltage stabilizer • Well aerated room • Locked, open when necessary • Defrost periodically • Dial thermometer

23. DONTs • No objects on ILR • Don’t store drugs • Drinking water/ food • Expired vaccines

24. Contd.. • Cold box: • Peripheral centres • Transport of vaccines • Before placing vaccines, fully frozen ice packs at bottom • DPT, DT, TT- not in direct contact with frozen ice packs

25. Contd.. • Vaccine carriers: • Small quantities ( 16-20 vials) of vaccines- out of reach stations • 4 fully frozen ice packs

26. Vaccine carriers

27. Contd… • Day carriers: • 6-8 vials, transport nearby place • 2 ice packs • Ice packs: • Contain water, no salt added • Level made: water marked upto that • Leak: discarded.

28. Ice packs

29. Steps in investigation of epidemic • Verification of diagnosis: first step, not necessary to examine all cases- take sample • Confirmation of existence of epidemic: 2 standard errors from endemic occurrence

30. Steps in investigation of epidemic • Define population at risk : obtain area map, calculate denominator-population at risk • Rapid search for cases and characteristics: medical survey, epidemiological case sheet, search for more cases- till area declared free of epidemic- twice incubation period of disease since appearance of last case

31. Steps in investigation of epidemic • Data analysis: time-epidemic curve, place-spot map, person • Formulate hypothesis • Test hypothesis • Further evaluation • Write report

32. Types of disinfection • Concurrent: after discharge-infectious material: urine, faeces, vomit, stool • Terminal: after disease agent removed from body ; disinfecting bedsheets, linen after death of patient • Precurrent (Prophylactic): handwashing, pasteurization

33. Adverse Events Following Immunization (AEFI) • Medical incident: after immunization- caused by immunization. • Vaccine reactions: Vaccine given correctly; Caused by properties of vaccine; Common minor reactions; Hypersensitivity- anaphylactic shock, serum sickness • Immunization error related reactions : Faulty techniques; Incorrect dose, diluent; Vaccine stored incorrectly

34. AEFI • Immunization anxiety related reactions: fainting, headache • Coincidental events: Unconnected with vaccine

35. Incubation period (IP) • Time between invasion: infectious agent-sign and symptom • Median IP: time : 50% cases occur • Latent period: • For non-infectious diseases • Period from disease initiation and detection

36. Importance • Trace source of infection • Immunization • Prognosis • Determine period of surveillance

37. Continued….. • Serial interval: • Gap between onset : primary and secondary cases • Generation time: • Interval: receipt of infection-maximal infectivity • Communicable period: • Time : infectious agent: transferred : person-person

39. New National Immunization Schedule , 2016 • Birth: BCG, Hep B, OPV 0 • 6 weeks: OPV 1, DPT 1, Hep B 1, HiB1, RotaV1, IPV • 10 weeks: OPV 2, DPT 2, Hep B 2, HiB2, RotaV2 • 14 weeks: OPV 3, DPT 3, Hep 3,HiB3, RotaV3 IPV • 9 months: Measles, Vitamin A • 16-24 months: DPT, OPV booster, Measles (2nd disease), JE, Vitamin A • 5-6 years: DPT booster • 10, 16 years: TT

40. Multiple Choice Questions (MCQs) 8. All the following are used as proxy measures for incubation period except: • Latent period b. Period of communicability c. Serial interval d. Generation time b. Period of communicability

41. MCQs 9. Carrier has no role in transmission of a. Cholera b. Typhoid c. Diphtheria d. Measles d. Measles

42. Carriers • Inadequate treatment/immune response: disease agent not eliminated: carrier • Infected person/ animal: harbours infectious agent, absence of disease, infect others

43. Continued…. • Temporary • Chronic • Incubatory: measles • Convalescent: diphtheria • Healthy: polio

44. MCQs 10. Which of the following is not a killed vaccine? • DPT b. Rabies c. Hepatitis B d. Rubella d. Rubella

45. Vaccines • Live vaccine: Attenuation: organisms passed repeatedly: laboratory/tissue culture; Lost potential: full-blown diseases; Examples: BCG, Measles, Chicken Pox, Oral Polio • Killed vaccine: Killed: heat/chemicals; Safe, less efficacious; Examples: Rabies, Hepatitis B, Typhoid, cholera • Toxoids: Exotoxins: diphtheria, tetanus; Detoxicated, used to prepare vaccines • Cellular fractions: meningococcal vaccine • Combination of vaccines: Pentavalent

46. MCQs 11. Screening fever cases for malaria during home visits by Multipurpose Workers is……………………. a. Active surveillance b. Passive surveillance c. National surveillance d. Sentinel surveillance a. Active surveillance

47. Surveillance • Continuous scrutiny: all aspects of occurrence, spread-effective control • Types: Individual/Local population/ National population/ International surveillance • Active/ passive • Uses of surveillance: Information about trends of disease, feedback to modify system, timely warning of epidemics

48. Thank you 