Air Borne Infection: Epidemiology and control measures

1. Air Borne Infection:Epidemiology and control measures Moderator: Prof.A.M.Mehendale Presenter : Dr.Rohan

2. Defination • Epidemiology is the study of the distribution and determinants of health-related states or events (including disease), and the application of this study to the control of diseases and other health problems ’ - John M. Last(1988)

3. Communicable Diseases: A communicable (or infectious) disease is one caused by transmission of a specific pathogenic agent to a susceptible host. • Directly, from other infected humans or animals, or • Indirectly, through vectors, airborne particles or vehicles.

4. Theories of Disease Causation • Theory of humors (humor means fluid): • The miasmatic theory of disease • Theory of contagion • Germ theory • Koch’s postulates

5. Epidemiological triad

6. Epidemiological triad • r Agent Factors Physical Agents Chemical Agents Biological Agents Nutritional agents Host Factors Socio-demographic Factors Psycho-social Factors Intrinsic Characteristics Environmental Factors Physical Environment Biological Environment Social Environment

7. Impact of communicable Diseases • Six causes account for almost half of all premature deaths, mostly in children and young adults, and account for almost 80% of all deaths from infectious diseases: • Acute respiratory infections (3.76 million) • HIV/AIDS (2.8 million) • Diarrhoeal diseases (1.7 million) • Tuberculosis (1.6 million) • Malaria (1 million) • Measles (0.8 million)

8. Definitions

9. Epidemic Epidemics are defined as the occurrence of cases in excess of what is normally expected in a community or region. Epidemic varies according • agent, • the size, type • susceptibility of population exposed, • and the time and place of occurrence.

10. Agent ‘A substance, living or non living, or a force, tangible or intangible, the excessive presence or relative lack of which may initiate or perpetuate a disease process’ Biological Nutrient Physical Chemical Mechanical Social

11. r • The pathogenicity of the agent: its ability to produce disease, measured by the ratio of the number of persons developing clinical illness to the number exposed. • Virulence: a measure of the severity of disease, which can vary from very low to very high. • Infective dose: the amount required to cause infection in susceptible subjects. • The source of infection: the person or object from which the host acquires the agent.

12. Host ‘the person or animal that provides a suitable place for an infectious agent to grow and multiply under natural conditions’ • Intrinsic Demographic characteristics Biological characteristics Socio-economic Lifestyle characteristics

13. r • The incubation period—the time between entry of the infectious agent and the appearance of the first sign or symptom of the disease. • Environment (Extrinsic) Physical Enviornment Bilogical Environment Psychosocial Enviornment

14. Air Borne Disease: “A mechanism of transmission of an infectious agent by particles, dust or droplet nuclei suspended in air” Two types of particles are implicated the airborne form of spread of infectious agent • Droplet Nuclei • Droplet Particles

15. Droplet Nuclei • tiny particles (1-10 microns) that • represent the dried residue of droplets. • Smaller particles (<3 microns) in diameter may contain one or two micro-organism which fail to settle due to gravity and • remain suspended in the atmosphere for long periods of time.

16. Dust Larger droplets which are expelled during talking, coughing or sneezing, settle down by their sheer weight on the floor and other objects in the immediate environment. • streptococci, viruses and fungal spores and skin squmae have been found in the dust. • Some of them as TB bacilli may remain viable under optimum condition of temperature and moisture. • Dust released becomes infective again. This type of transmission is more common in hospital settings.

17. Fig.Partticle size and presence of particulate matters with settling velocity • r

18. Agent Factors:Main agent in Air borne infection are viruses, bacterias or Fungal spores • r

19. Source Of Infection: Either clinical, Subclinical case or carriers • r • Infections caused by clinical case: • Chicken pox • Measles • Rubella • Mumps (no sub-clinical case) • Influenza • Diphtheria • Pertussis (no sub-clinical case) • Mycobacterim TB Carrier: • Diphetheria (95%) • Meningococcal Meningitis(70-80%) • Mycobacterium TB

20. Incubation Period: • All the viral infections have short incubation period varying from 1-3weeks. • Shortest incubation period is for influenza which is 18 to 72 hours. In case of Bacterial infections incubation period is as: Diphtheria 2-6 days Pertussis (no sub-clinical case) 7-14 days Meningococcal Meningitis 2-10 days

21. r • r Period of communicability: Highly infectious in early stage of disease (Prodromal Period) Secondary attack Rate: Secondary attack rate is highest in case of Chickenpox 90% and Mumps 86%. In case of bacterial infection if person is unimmunized it may range to 90% (Pertussis) All viral infections confers lifelong immunity (once attacked)

22. r • Infective material: Nasopharyngeal, Bronchial secretions or skin squmae can also be source of infection. Host Factors: • Age: Most susceptible age group is 6months-3 yrs more common in less than 5yrs of age and elderly people except influenza which is common in all ages.

23. r • Sex: Both the sexes are equally susceptible • Human mobility: Infections are more common in people who are generally mobile on duty.

24. Environmental Factors: • Air borne infection is more common in the winter and spring region. • In India Influenza infection is more common in the summer season. • Diphtheria, Measles are common in all the season. • Winter season favors the transmission due to dampness and humidity. • Overcrowding favors the transmission of the air borne infection.

25. Environmental Factors The following factors have been associated with the emergence and spread of infectious diseases • the changes in human demographics and behaviour • the impact of new technologies and industries • economic development and changes in land use • increased international travel and commerce • microbial adaptation and change • the breakdown of public health measures, and • Sharing an environment with domestic or wild animals or birds

26. Mechanism of Air Borne Infection:

27. Air Borne infection Control

28. Early Recognition Rapid identification of Patients Prone of air borne Diseases: • Clinical indications: • Unexplained cough • Severe acute febrile respiratory illness (e.g., fever > 38°C, cough, shortness of breath) • Exposure history consistent with ARD of potential concern • Epidemiological indications • History of travel to area affected by ARDs • Possible occupational exposure • Unprotected contact with ARDs patient(s)

29. Standard Precautions • Hand hygiene • Respiratory hygiene/cough etiquette • Use of personal protective equipment (PPE) • Prevention of needle sticks/sharps injuries • Cleaning and disinfection of the environment and equipment

30. Hand Hygiene • Hand hygiene should be performed: • before and after any direct contact with a patient • after contact with blood, body fluids, secretions and excretions • after contact with items contaminated with blood, body fluids, secretions and excretions, including respiratory secretions • Use alcohol-based hand rub or wash hands with soap and water • Wash hands if visibly soiled

31. Respiratory Hygiene/Cough Etiquette

32. Droplet Precautions • Protection against respiratory pathogens transmitted by large droplets • In addition to Standard Precautions: • Use a medical mask when < 1 m of patient • Maintain a distance ≥ 1 meter between infectious patient and others • Place patient in a single room or cohort with similar patients • Limit movement

33. Administrative controls •Isolation/separation •Masks •Effective treatment Respiratory Protectio Environmental Controls Dilution (ventilation) Removal (Fans) Decontamination (UVGI)

34. AIRBORNE PRECAUTIONS • Private room with monitored negative air pressure • 6-12 air changes per hour • High efficiency particulate air (HEPA) filtration for recirculated air • HCWs wear respirators (minimum N95) • Limit patient movement/transport

35. AIRBORNE PRECAUTIONS

36. Personal Protective Equipment • Types of PPE Used in Healthcare Settings • Gloves – protect hands • Gowns/aprons – protect skin and/or clothing • Masks and respirators– protect mouth/nose • Respirators – protect respiratory tract from airborne infectious agents • Goggles – protect eyes • Face shields – protect face, mouth, nose, and eyes

37. PPE for Standard Precautions: Based on Risk Assessment • IF direct contact with blood & body fluids, secretions, excretions, mucous membranes, non-intact skin • Gloves • Gown • IF there is the risk of spills onto the body and/or face • Gloves • Gown • Face protection (mask plus eye protection goggle or visor; face shield)

38. r • Contact Precautions • Gloves • Gown • Droplet Precautions • Medical mask • Airborne Precautions • Particulate respirator

39. References: • 1. Last JM. A Dictionary of medical epidemiology, 4th edition. • 2. LangmuirA. D. (1961). "Epidemiology of airborne infection." Bacteriology Reviews 25: 173-181. • 3. Hill AB. The environment and disease: association or causation? Proc R Soc Med 1965;58: 295-300. • 4. Park K. Park’s textbook of preventive & social medicine. 19th ed. Jabalpur: M/s Bhanarsidas Bhanot publishers; 2007. • 5. R. Bonita, R. Beaglehole, T. Kjellström. Basic epidemiology / 2nd edition. Epidemiology. World Health Organization • 6. Infection prevention and control of epidemic- and pandemic-prone acute respiratory diseases in health care WHO Interim Guidelines, 2007.