EPIDEMIOLOGY

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EPIDEMIOLOGY
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MORBIDITY VS MORTALITY

• SUVEILLANCE OF DISEASE OCCURRENCE
• REPORTING SYSTEM FROM INDIVIDUAL DOCTORS TO
  COUNTY, STATE AND FEDERAL PUBLIC HEALTH OFFICIALS
• CENTERS FOR DISEASE CONTROL AND PREVENTION
• IN ATLANTA GEORGIA

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STATISTICS AND EPIDEMIOLOGY

• PROBABILITY OF EXPOSURE
• PROBABILITY OF TRANSMISSION

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HISTORY OF EPIDEMIOLOGY

• JOHN SNOW AND CHOLERA

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TYPES OF STUDIES

• DESCRIPTIVE EPIDEMIOLOGY
• ANALYTICAL EPIDEMIOLOGYEXPERIMENTAL STUDIES

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DESCRIPTIVE EPIDEMIOLOGICAL STUDIES

• DESCRIBES PATTERNS OF DISEASE IN POPULATIONS
  USING AGE, GENDER, GEOGRAPHIC AREA AND TIME OF
  OCCURENCE

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ESCHERICHIA COLI

• E. COLI O157H7
• JANUARY 1993 -WASHINGTON STATE
• SEVERE BLOODY DIARRHEA
• FOUND IN HAMBURGER MEAT

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ANALYTICAL EPIDEMIOLOGICAL STUDIES

• USE SCIENTIFIC METHOD
• ESTABLISHES CAUSE AND EFFECT RELATIONSHIPS
• COHORT STUDY
• CASE CONTROL STUDY

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COHORT STUDY

• MOST DEFINITIVE
• STUDY GROUPS WITH AND WITHOUT RISK FACTORS
• LEGIONAIRES DISEASE

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CASE CONTROL STUDY

• INDIVIDUALS WITH DISEASE ARE COMPARED WITH THOSE
  WITHOUT
• HANTAVIRUS

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EXPERIMENTAL STUDIES

• ANIMAL STUDIES
• HUMAN STUDIES

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TERMS OF EPIDEMIOLOGY

• INCIDENCE
• NUMBER OF NEW CASES SEEN IN A SPECIFIC TIME
  PERIOD
• PREVELANCE
• TOTAL NUMBER OF CASES AT ANY ONE TIME

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MORBIDITY RATE

• EXPRESSED AS CASES PER 10,000 PER YEAR

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MORTALITY RATE

• NUMBER OF INDIVIDUALS WHO DIE AS OF A SPECIFIC
  DISEASE
• PUBLISHED IN MORBIDITY AND MORTALITY WEEKLY
  REPORTS

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PATTERNS OF DISEASE OCCURENCE

• ENDEMIC, EPIDEMIC, PANDEMIC AND SPORADIC DISEASES

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ENDEMIC DISEASE

• CONSTANTLY PRESENT
• PARTICULAR GEOGRAPHIC AREA
• INVOLVES RELATIVELY FEW INDIVIDUALS
• NOT MAJOR HEALTH PROBLEM
• TUBERCULOSIS AND MUMPS IN US
• GONORRHEA AND CHANCROID IN WORLD

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EPIDEMIC DISEASE

• UNUSUAL OCCURENCE OF DISEASE
• INVOLVES LARGE SEGMENT OF POPULATION
• FOR LIMITED TIME
• ENDEMIC DISEASES CAN BECOME EPIDEMIC
• INFLUENZA, MEASLES AND CHICKEN POX

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PANDEMIC DISEASE

• SERIES OF EPIDEMICS
• AFFECT SEVERAL COUNTRIES
• MAJOR PORTIONS OF THE WORLD
• INFLUENZA PANDEMIC OF 1918-1919
• HIV AND AIDS
• GENITAL HERPES AND GENITAL WARTS

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SPORADIC DISEASES

• UNCOMMON
• OCCUR IRREGULARLY
• AFFECT FEW PEOPLE
• DIPHTHERIA AND WHOOPING COUGH
• CAN OCCASIONALLY BECOME EPIDEMIC

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TYPES OF EPIDEMICS

• COMMON SOURCE
• PERSON TO PERSON
• http//uhavax.hartford.edu/bugl/histepi.htm
• http//en.allexperts.com/e/e/ep/epidemic.htm

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COMMON SOURCE EPIDEMICS

• SINGLE EXPOSURE SOURCE
• RAPID ONSET OF DISEASE CASES
• RAPID DECLINE OF DISEASE CASES

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PERSON TO PERSON EPIDEMIC

• PROPOGATED
• SLOW PROLONGED RISE OF CASES
• SLOW PROLONGED DECLINE IN CASES

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INFLUENZA EPIDEMICS

• PRIME EXAMPLE OF PERSON TO PERSON EPIDEMICS
• WORLD HEALTH ORGANIZATION TRIES TO LIMIT BY
  VACCINES
• SOMETIMES WORKS SOMETIMES NOT

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DISEASE TRANSMISSION
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RESERVOIRS

• SUPPORTS SURVIVAL, MULTIPLICATION, AND
  TRANSMISSION
• LIVING RESERVOIRS
• NONLIVING RESERVOIRS

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TERMS

• VECTORS
• VEHICLES
• FOMITES

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HUMAN RESERVOIRS

• MOST HUMAN PATHOGENS CANNOT LIVE OUTSIDE HOST
  LONG
• MANY RESTICTED ALMOST ENTIRELY TO HUMANS

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POTENTIALSOURCES

• BODY FLUIDS
• FECES
• URINE
• SEMEN AND DISCHARGES FROM GENITOURINARY TRACT
• SALIVA FROM MOUTH
• MUCUS FROM RESPIRATORY TRACT
• BLOOD
• DISCHARGES FROM SORES AND WOUNDS

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CARRIERS

• HOST WHO HARBORS PATHOGENS THAT ARE TRANSMISSIBLE
  TO OTHERS
• HEALTHY CARRIERS
• INCUBATORY CARRIERS
• CONVALESCENT CARRIERS
• INTERMITTENT CARRIERS

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ZOONOSES VECTOR TRANSMITTED DISEASES

• RABIES
• YELLOW FEVER
• PLAGUE
• ROCKY MOUNTAIN SPOTTED FEVER
• TYPHUS FEVER
• LYME DISEASE

• LEISHMANIASIS
• AFRICAN SLEEPING SICKNESS
• CHAGAS DISEASE
• VIRAL ENCEPHALITIS
• MALARIA

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NONLIVING RESERVOIRS

• FOMITES
• VEHICLES

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PORTALS OF ENTRY

• SKIN
• MUCOUS MEMBRANES
• RESPIRATORY
• GASTROINTESTINAL TRACT
• URINARY TRACT
• PARAENTERAL ROUTE
• WOUNDS, ANIMAL BITES, INJURIES
• PATHOGENS ARE GENERALLY RESTRICTED TO SPECIFIC
  PORTALS

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INFECTIOUS DOSE

• NUMBER OF PATHOGENS NEEDED TO CAUSE DISEASE
• VARIES FROM ONE TO HUNDREDS OF THOUSANDS
• HIV REQUIRES LARGE DOSES
• ENCAPSULATED STREPTOCOCCUS PNEUMONIAE JUST A FEW
• PATHOGEN MUST OVERCOME HOST DEFENSES

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FACTORS THAT AFFECT INFECTIOUS DOSE

• HOST DEFENSES
• ABILITY OF MICROBE TO OVERCOME DEFENSES
• MALNUTRITION
• IMMUNITY OF HOST

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PORTALS OF EXIT

• DISCHARGED WITH BODY FLUIDS AND WASTES
• SNEEZING, COUGHING , TALKING
• VAGINA AND SEMEN SECRETIONS

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TRANSMISSION

• AIRBORNE TRANSMISSION
• VEHICLE TRANSMISSION FOOD WATER
• DIRECT SEXUAL CONTACT
• VECTOR TRANSMISSION ZOONOSES
• DIRECT SKIN CONTACT
• NOSOCOMIAL TRANSMISSION
• TRANSMISSION BY BODY FLUIDS

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AIRBORNE TRANSMISSION

• COMMON CORYZA
• INFLUENZA
• LEGIONNAIRES DISEASE
• TUBERCULOSIS
• HISTOPLASMOSIS
• COCCIDIOMYCOSIS

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VEHICLE TRANSMISSION-

• FOOD POISONING OR INTOXICATION
• INFECTIONS

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FOOD POISONING OR INTOXICATAION

• STAPHYLOCOCCAL FOOD POISONING
• BOTULISM

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GASTROENTERITIS AND ENTEROCOLITIS

• TYPHOID FEVER
• SHIGELLOSIS
• HEPATITIS
• GIARDIASIS
• CYRPTOSPORIDISOSIS
• TOXOPLASMOSIS
• YERSINIOSIS

• VIRAL GASTROENTERITIS
• BACTERIAL GASTROENTERITIS
• BACTERIAL ENTEROCOLITIS
• E. COLI O157H7

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SEXUALLY TRANSMITTED DISEASES

• AIDS
• GENITAL HERPES
• GENITAL WARTS
• GONORRHEA
• SYPHILIS
• NONGONOCOCCAL URETHRITIS

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DIRECT TRANSMISSION BY SKIN CONTACT

• WARTS
• LEPROSY
• TINEA

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INDIRECT CONTACT

• FOMITES ARE CONTAMINATED WITH PATHOGENS

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VECTORS

• ARTHROPODS ARE MOST COMMON VECTOR
• MECHANICAL TRANSMISSION
• BIOLOGICAL TRANSMISSION

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MECHANICAL TRANSMISSION

• SIMPLE PASSIVE TRANSPORT
• PATHOGENS ARE CARRIED ON INSECTS (USUALLY) FEET
  OR BODY PARTS
• FLIES ON FOOD

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BIOLOGICAL TRANSMISSION

• MORE COMPLEX
• PATHOGENS REPRODUCE BOTH IN VECTOR AND HOST

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ALTERNATE HOST

• HOST WHERE ASEXUAL REPRODUCTION OCCURS

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DETERMINANT HOST

• HOST WHERE SEXUAL REPRODUCTION OCCURS

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NOSOCOMIAL INFECTIONS

• SERUM HEPATITIS
• PUERPERAL FEVER\INFECTIONS AFTER SURGERY

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• SERUM HEPATITIS
• EBOLA

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DISEASE PREVENTION

• REMOVAL OF PATHOGEN FROM FOOD AND WATER SOURCES
• VECTOR CONTROL
• ISOLATION AND QUARANTINE
• VACCINATION
• http//www.who.int/water_sanitation_health/hygiene
  /emergencies/em2002chap11.pdf

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REMOVAL OF PATHOGENS FROM FOOD AND WATER

• SEWAGE TREATMENT
• WATER TREATMENT
• PASTEURIZATION
• CANNING OF FOOD

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VECTOR CONTROL

• REDUCE INSECT NUMBERS LICE MOSQUITOS
  TICKS FLEAS

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ISOLATION AND QUARANTINE

• PREVENT EXPOSURE OF OTHER TO DISEASE PATHOGENS

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VACCINATIONS

• ATTEMPTING TO MAKE IMMUNOLOGICAL MEMORY
• HERD IMMUNITY

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TYPES OF VACCINATIONS

• TOXOIDS
• KILLED MICROBE
• INACTIVATED MICROBE
• ATTENUATED MICROBE
• INDIVIDUAL COMPONENTS OF MICROBE
• VECTOR VACCINES

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BOOSTER VACCINES

• GIVES MULTIPLE EXPOSURES TO ANTIGEN
• MAINTAINS IMMUNOLOGICAL MEMORY

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TYPES OF VACCINATIONS

• INTRADERMAL
• SUBCUTANEOUS
• INTRAMUSCULAR
• INTRAVENOUS
• ORALLY

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ROLE OF ADJUVANTS

• CHEMICALS THAT ENHANCE ANTIGENICITY
• ALUMINUM
• ALUM

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VACCINES FOR PREVENTION OF OF DISEASES

• PROPHYLAXIS
• TETANUS
• RABIES