1. Epidemiology and Public Health (Two Lectures) BY Prof. DR. Zainalabideen A. Abdulla, DTM&H., MRCPI, Ph.D., FRCPath. (U.K.)

2. Learning Objectives

3. Epidemiology Is the study of factors that determine the frequency, distribution, and determinants of diseases in human populations. - Microbiology & infectious diseases - Terminology - John Snow is the father of epidemiology (conducted a study in London about Cholera transmission; end of 19 th century)

4. Infectious disease: Caused by a pathogen Communicable disease: Transmissible (person TO person) e.g. Gonorrhea Contagious disease: Easily transmitted e.g. Influenza Zoonotic diseases (zoonosis): Animal Humans

5. Incidence Number of NEW cases of a disease in a defined population during a specific time period Morbidity : The same, but per a specifically defined population (e.g. 1,000, 10,000, 100,000)

6. Prevalence Period Prevalence: Total number of cases in a given population during specific time period (e.g. in 2012) Point prevalence: The same but in a particular moment (e.g. now)

7. Mortality Rate (Death Rate) Number of deaths of a particular disease during a specific time period per a specified population (per 1,000, 10,000, 100,000) Sporadic Diseases Diseases occur occasionally within a population of a particular area, e.g. Cholera in USA

8. Endemic diseases Always present within the population of a particular area, e.g. tuberculosis in USA Epidemic Diseases A greater than usual number of cases of a disease in a particular region occurring within a relatively short period of time, e.g. fungal meningitis in 2012 in USA.

9. Waterborne disease outbreaks From drinking (e.g. bacteria, viruses, parasites) or recreational (e.g. Cryptosporidium) water Foodborne disease outbreaks Norovirus most common in USA

10. Pandemic Disease A disease occurring in epidemic proportions in many countries simultaneously/worldwide, e.g. Spanish flu in 20 th century (killed 20 millions) Most Common Pandemic Diseases HIV/AIDS Tuberculosis Malaria - > 300 million; > 5 million deaths

11. HIV/AIDS - Epidemic started 1979 (recorded 1981) in USA Now > 1 million with HIV in USA) Worldwide: 35 million - HIV1 and HIV2 viruses - 10-15 years to develop after HIV infection - Different modes of transmission

13. Tuberculosis Multidrug-resistant tuberculosis (MDR-TB) Extensively drug-resistant tuberculosis (XDR-TB) Second killer after HIV/AIDS. 1/3 of the world population infected with TB (Latent TB) Leading killer of AIDS patients

14. Malaria 5 th leading cause of death worldwide (RTI, HIV/AIDS, diarrhea, TB) Most common in sub-Saharan Africa Half world’s population at risk > ½ million deaths worldwide; every 1 minute 1 child die in Africa (second leading cause of death after AIDS)

15. Interaction: pathogens, hosts & environment I. Pathogens Virulence Portal of entry Numbers II. Host Health status Nutritional status Susceptibility cont./…

16. cont./…Interactions IIII. Environment: Physical factors Reservoirs Sanitary/housing Infectious disease Virulence X Numbers vs Host Factors

17. Chain of Infection 1. Pathogen 2. Reservoir 3. Portal of exit 4. Mode of transmission 5. Portal of entry 6. Susceptible host

19. Strategies of breaking the chain of infection Broad goals: Eliminate/contain Reservoir Prevent contact with Exit Eliminate transmission Block entry Reduce/eliminate susceptibility cont./…

20. cont./… Strategies of breaking chain Specific methods: Hand hygiene Good nutrition Immunization Insect/rodent control Patient isolation Decontamination Wastes disposal Sanitation and safety measures

21. Reservoirs of infections Is any site where the pathogen can multiply or survive until transferred to a host. Reservoirs: Living hosts Inanimate objects

23. Human carriers Other humans (patients or carriers) Carrier = With pathogens, but no disease: - Passive: Never had the disease - Incubatory: Transfer disease during I.P. - Convalescent: Transfer disease during recovery period - Active: Completely recovered, continue to harbor the pathogen indefinitely (e.g. Mary Mallon: Typhoid Mary)

24. Animals Zoonotic diseases: Humans acquired them from animal sources via direct contact, inhalation, ingestion, or injection by arthropod. Examples (Table):. Rabies. Toxoplasmosis. Salmonellosis. Variant CJ disease. Anthrax (B. anthracis). Brucellosis, Campylobacteriosis

27. Arthropods (vectors). Insects (e.g. mosquitoes, lice, fleas, flies). Arachnids (e.g. mites, ticks) Blood (pathogen) Healthy Individual e.g. Malaria - Table/Figure

30. Nonliving reservoirs Air, soil, dust, food, milk, water and fomites Air contaminated by human secretions: Talk, breathing, sneezing, and coughing; or via air vents/current Most contagious: Colds and Influenza Dust: Carry bacteria and spores, fungi- dried cont./…

31. cont./… nonliving reservoirs Soil: Spores (e.g. Clostridium: tetanus, botulism, gas gangrene) Food & Milk: Pathogens Food poisoning (Dirty hands, soil, dust, hair, secretions, etc) Examples: Amebiasis, Cholera, hepatitis A Fomites: Gowns, towels, utensils, equipment contaminated by RT, GIT, skin) Dust: Carry bacteria and spores, fungi- dried

33. Modes of transmission Contact, Droplet, Airborne, Vehicular, Vector Droplets: 5 µm or more in diameter Coughing, sneezing, talking Airborne: Dispersal of droplet nuclei (residue of evaporated droplets) < 5 µm Vehicular: Food, water, dusts, fomites - Contact (direct & indirect); Vector: Discussed

35. Communicable diseases Infectious diseases transmitted from person to persons via: 1. Direct skin-to-skin contact Common cold virus- by hands shaking Healthcare workers: Wash hands 2. Direct mm-to-mm by kissing/sexual contact Most STD (Chlamydia “ most common notifiable disease in USA”, syphilis, gonorrhea, HIV, and herpes virus) cont./…

36. cont./… communicable diseases transmission 3. Indirect contact via airborne droplets of respiratory secretions, usually produced as a result of sneezing or coughing: Most contagious airborne diseases Pathogens carried by dust Colds, influenza, measles, mumps, chickenpox, smallpox, pneumonia

37. cont./… communicable diseases transmission 3. Indirect contact via food and water contamination with fecal material Restaurant food handlers 4. Indirect contact via arthropod vectors 5. Indirect contact via fomites that become contaminated by respiratory secretions, blood, urine, feces, vomitus, or exudates from hospitalized patients Table cont./…

38. cont./… communicable diseases transmission 6. Indirect contact via transfusion of contaminated blood or blood products from an ill person or by parenteral injection (injection directly into the blood-stream) using nonsterile syringes and needles, so: Disposable materials used in hospitals

41. Public Health Agencies 1. World Health Organization (WHO) Founded in 1948 Epidemiological terms regarding an infectious disease (Table): - Control - Elimination - Eradication cont./…

43. cont./… public health agencies 2. The Centers for Disease Control and Prevention (CDC):. USA, founded in 1946. Aspects of epidemiology/microbiology. Notifiable diseases should be reported. Table: ¾ top- are sexually transmitted, 2/10 are vaccine-preventable

45. Bioterrorism and Biological Warfare Agents Anthrax Cause: B. anthracis /G+, spore-forming B Forms: Inhalation, GI, cutaneous (Eschar) “according to severity” Involve: Hemorrhage, serous effusion Spread/spores: Aerosols, food, mail Prevention: Antibiotic therapy

48. Botulism Cause: Clostridium botulinum Toxin (neurotoxin)/ G+ spore-forming bacilli Nerve damage, visual difficulty, respiratory failure, flaccid paralysis, brain damage, death Source: Toxin to water supply, food, or spores into open wounds

49. Smallpox Serious, contagious fatal Fever, malaise, headache, prostration, severe backache, skin rash bleeding into skin and mm WHO: 1980 eradicated No need for vaccination Preserved virus Risk to wrong hands

51. Plaque (Black Death) Cause: Yersinia pestis/ G- coccobacilli Zoonosis, transmitted by flea bites Types: Bubonic, septicemic, pneumonic, and meningitis Transmission: Aerosols, person-to-person Bubonic: Swollen, inflamed, tender L.N. (buboes) Pneumonic: Highly communicable/lungs Septicemic: Cause septic shock and meningitis

56. Water supply pollution 1. Chemical 2. Biological Sources Rainwater falling Sewage into rivers Shallow water vs deep wells Cracked water pipes

59. Water treatment Filter Sedimentation or settling Coagulation/flocculation: Alum (Aluminum K Sulfate) Sand filter (remove organisms) Membrane filters (Tiny cysts: Giardia lamblia, Cryptosporidium 4-6 µm) Check contamination (fecal- Coliforms): E. coli, Enterobacter, Klebsiella: Safe = 1 coliform /100 ml water or less Common: G. lamblia, Cryptosporidium, E. coli O157:H7, Shigella, and norovirus Boiling 20 min kill tiny organisms, not spores or viruses

60. Sewage treatment Primary sewage Filter (screening), skimmer removed, settle, flocculation Primary sludge Secondary sewage: Primary effluent Aeration and trickling (aerobic microbes break organic into CO2 & H2O) settle Secondary effluent filter/chlorinated River Tertiary Sewage To drinking water, expensive, need to treat