EPIDEMIOLOGY – STUDY OF FACTORS AFFECTING HEALTH/ILLNESS; MONITOR PUBLIC HEALTH:

REPORT MORBIDITY/MORTALITY RATESRESPOND TO: DISEASE OUTBREAKS, EPIDEMICS, PANDEMICS:

DETERMINE CAUSES, INSTITUTE CONTROLINVESTIGATE EMERGING/RE-EMERGING DISEASES

DETERMINE RISK FACTORS/INSTITUTE CONTROL

CDC – CENTERS FOR DISEASE CONTROL & PREVENTIONWHO - WORLD HEALTH ORGANIZATION

ENDEMIC, SPORADIC OUTBREAK, EPIDEMIC, PANDEMICINDEX CASE = FIRST CASE IN EPIDEMIC

Figure 28-23 Locations of some emerging and reemerging infectious diseases.

JOHN SNOW – FIRST EPIDEMIOLOGIST – ENGLISH PHYSICIANSTUDIED CHOLERA OUTBREAKS IN LONDON – ~1840-1854VIBRIO CHOLERAE – BEFORE GERM THEORY OF DISEASE

CONVINCED BY OBSERVATION – CHOLERA SPREAD BY UNCLEANHANDS/SHARED FOOD

1849 – OUTBREAK – SNOW SUSPECTED WATER AS SOURCEMAPPED DEATHS FROM OFFICIAL RECORDS,CLUSTERED AROUND ONE WATER PUMP ON BROAD STREET. REMOVED PUMP HANDLE, NUMBER CASES DROPPED

Figure 28-20 Early epidemiology ACTUALLY THE FIRST EPIDEMIOLOGY.

1854 OUTBREAK TWO WATER PROVIDERS (FOR AFFECTED AREA)SOUTHWARK/VAUXHALL AND LAMBETHPATIENT INTERVIEWS - SNOW –

MOST VICTIMS (~88%) –WATER FROM S/V COMPANYS/V TOOK WATER FROM THAMES BELOW SEWAGE DISCHARGELAMBETH TOOK WATER FROM THAMES ALSO, BUT ABOVE

SEWAGE DISCHARGESNOW – WATER CONTAMINATED BY SEWAGE WAS RESPONSIBLE

& THE AGENT WAS ABLE TO MULIPLY IN WATER

USED: CASE REPORTING / MAPPING

SURVEILLANCE POPULATION SURVEYS – E.G., IMMUNIZATION RECORDS

EVALUATE EFFECTIVENESS IN CONTROLLING SPECIFIC INFECTION CASE REPORTING – ALLOW LOOKING BACK TO DETERMINE SPECIFIC

CONDITIONS WHICH PUT PEOPLE AT RISK

TOOLSCASE REPORTS – MORBIDITY DATA

NOTIFIABLE DISEASES – MUST BE REPORTED TO CDC:E.G., ANTHRAX, CHLAMYDIA, CHOLERA, LEGIONELLOSIS’PERTUSSIS, TUBERCULOSIS, VACOMYCIN-RESISTANT STAPHAUREUS (VRSA)HANTA VIRUS, HIV, MUMPSCOCCIDIOIDOMYCOSIS

MORTALITY DATA – DEATH CERTIFICATES

INVESTIGATE ACTUAL CASES –INTERVIEW HIV+ PEOPLE TO IDENTIFY PARTNERS

REMOTE SENSING & GEOGRAPHIC MAPPING IMAGES OF EARTH SURFACE FROM SATELLITES

BIOLOGICAL SENSORS (SENTINEL BIRDS)

GEOGRAPHIC INFORMATION SYSTEM - DISPLAY DATA ON MAPS, CORRELATE FEATURE MAPPED WITH DISEASE DISTRIBUTIONE.G., CORRELATE HABITATS OF MALARIA PARASITE AND MOSQUITO

VECTOR WITH MALARIA

INFECTIOUS DISEASE FREQUENCY INCIDENCE = NUMBER NEW CASES IN DEFINED AREA/DEFINED TIME PERIOD

OFTEN EXPRESSED PER UNIT OF POPULATION (E.G, 100,000)

MORBIDITY RATE = NUMBER NEW CASES DURING SPECIFIED TIME/NUMBER INDIVIDUALS IN POPULATION EXPRESSED AS PERCENTAGE

PREVALENCE RATE = TOTAL NUMBER CASES IN POPULATION/TOTAL POPULATION, EXPRESSED AS PERCENTAGE

MORTALITY RATE = NUMBER DEATHS DUE TO GIVEN DISEASE/TOTAL POPULATION WITH THAT DISEASE

PATTERNS OF INFECTIOUS DISEASES IN POPULATIONS

INFECTIOUS – RESULTS FROM VIRUSES, BACTERIA, FUNGI, PROTOZOA,HELMINTHS

COMMUNICABLE – SPREAD PERSON – PERSONRABIES IS INFECTIOUS, NOT COMMUNICABLE

EPIDEMICSCOMMON SOURCE – REACH PEAK 1-2 WEEKS; DECLINES EVERYBODY GETS DISEASE FROM ONE SOURCE LEGIONNAIRRE’S DISEASE -LEGIONELLOSIS LEGIONELLA PNEUMOPHILA – GRAM POSITIVE RODS SOIL/FRESHWATER, THRIVES IN SHOWERS/AIR CONDITIONING SYMBIOSIS WITH PROTISTS AIRBORNE SPREAD TO HUMAN RESPIRATORY SYSTEM MULTIPLY IN PHAGOSOMES OF MACROPHAGES IN ALVEOLI BRONCHOPNEUMONIA – DEATH 10-15% SYMPTOMATIC ERYTHROMYCIN/RIFAMPIN NOT COMMUNICABLE!!!

EPIDEMIC PROPAGATED – GRADUAL INCREASE FOLLOWED BY GRADUAL DECREASE

SINGLE INFECTED PERSON INTRODUCED INTO SUSCEPTIBLE POPULATIONCOMMUNICABLE DISEASESTREPTOCOCCUS PYOGENES SORE THROAT – NEW POPULATIONS OF SENSITIVE SCHOOL KIDS ARRIVE, ONE INFECTED KID INITIATES EPIDEMIC, PERSON-PERSON TRANSMISSION

HERD IMMUNITY - LARGE PERCENTAGE POPULATION HAS ACQUIRED IMMUNITY

ENDEMIC DISEASES EXIST EVEN WITH HERD IMMUNITY –INFECTED PEOPLE TRANSMIT TO OTHER SUSCEPTIBLE

E.G., STDs PATHOGENS ENTER HUMAN POPULATION FROM ANIMAL RESERVOIRS

E.G., RABIES

EPIDEMICS – PATHOGENS EVOLVE TO CIRCUMVENT IMMUNITYE.G., INFLUENZA VIRUS –

ANTIGENIC DRIFT – MUTATIONS IN ENVELOPE PROTEINSHEMAGLUTININ, NEURAMINIDASE

ANTIGENIC SHIFT – GENOMIC RNA MOLECULES REASSORTINFLUENZE REPLICATED IN BIRDS & MAMMALS

2009 H1N1 INFLUENZA PRODUCED BY ANTIGENIC SHIFT MIXED INFECTION OF INDIVIDUAL CELLS BY TWO OR MOREVIRUSES OF DUCK, PIG AND HUMAN STRAINS

EPIDEMIC INDENTIFICATION/CONTROL – GOAL: IDENTIFY INDEX CASE (PATIENT ZERO), IDENTIFY CONTACTS, TREAT

OR QUARANTINE

SARS - SEVERE ACUTE RESPIRATORY SYNDROME

EARLY 2003 – 23 YR OLD FEMALE HOSPITALIZED IN SINGAPORE – ATYPICAL PNEUMONIA

LEGIONELLA, CHLAMYDIA, MYCOPLASMA – NEGATIVENASOPHARYNGEAL ASPIRATE – VIRUS PARTICLES BY EM – CORONA VIRUS6 DAYS WITHOUT ISOLATION – 20 OTHERS INFECTED, CANADA/VIETNAM

[PATIENT ZERO – THIS LADY HAD VACATIONED IN HONG KONG – CERTAIN HOTEL – PROBABLY INFECTED BY PHYSICIAN WHO STAYED ON SAME FLOOR SAME TIME; RETURNED TO SINGAPORE, INFECTED THOSE OTHERS]

FEB 2003 – 305 CASES ATYPICAL PNEUMONIA REPORTED BY CHINA

MAR - WHO NAMES SARS NEW DISEASE, ISSUES TRAVEL ALERT, - WORLD-WIDE COOPERATION

APR - PRESIDENT BUSH AUTHORIZES QUARANTINE OF SARS PATIENTS

APR - VIRUS GENOME SEQUENCED – CANADA

APR - SARS VIRUS - A PREVIOUSLY UNKNOWN PATHOGENIC VIRUS

TOTAL TIME ~ 7 WEEKSDEATH RATE ~5%; TOTAL NUMBER DEATHS <1000

1975 – LEGIONELLOSIS DISEASE RECOGNIZED, 7 YEARS TO FIND CAUSE1981 - AIDS DISEASE RECOGNIZED, ACQUIRED IMMUNODEFICIENCY SYNDROME

PCP PNEUMOCYSTIS PNEUMONIA IN YOUNG OTHERWISE HEALTHY MALES3 YEARS TO ISOLATE HIV

IDENTIFYING SOURCE OF OUTBREAK:4 MONTH PERIOD NEW DELHI – 45 CASES PEDIATRIC POST-OPERATIVE

WOUND INFECTIONS32 SPECIMENS – STAINED AND CULTURED POSITIVE

MYCOBACTERIUM ABSCESSUS - ~4-12 WEEKS

FIND SOURCE AND CLEAN IT UP!CULTURED SAMPLES FROM VARIOUS SOURCES, INSTRUMENTS,FOUND MANY CULTURES/STRAINS OF MYCOBACTERIUMDID ANY OF THEM CAUSE OUTBREAK?

AMPLIFY SPECIFIC REGION OF CHROMOSOMES, CUT BY RESTRICTIONENZYMES, LOOK FOR DIFFERENT LENGTHS OF FRAGMENTSONE STRAIN - WATER TAP IN OPERATING ROOM &ONE STRAIN - DEFECTIVE AUTOCLAVEIDENTICAL TO THOSE FROM PATIENTS

Figure 28-9 Morphology, growth, and DNA fingerprinting of Mycobacterium tuberculosis.

FINDING THE SOURCE

2010- SALMONELLA ENTERICA SEROVAR ENTERITIDIS SALMONELLOSIS OUTBREAK– EGGS IN SHELL, >500,000,000 EGGS RECALLED, ~2000 CASESMAY – NOV

JULY – CDC REPORTED SUSTAINED INCREASE IN NUMBER OF S. ENTERITIDISWITH INDISTINGUISHABLE DNA RESTRICTION PATTERNEXPECTED ~1,600 CASES/ ACTUALLY ~3,600; ~2000 UNEXPECTED

PUBLIC HEALTH OFFICIALS – 29 RESTAURANTS WHERE >1 ILL PERSON HAD EATENEGGS SUSPECTED – THOSE PEOPLE HAD ALL EATEN EGGS

WHO SUPPLIED EGGS?WRIGHT COUNTY EGG – GALT, IOWA – HAD SUPPLIED EGGS TO 4

RESTAURANTSALSO POTENTIAL SOURCE – HILLANDALE FARMS, IOWA

MUST SHOW THAT ORGANISM CONTAMINATED THE FARMS –600 SAMPLES TESTED – MANURE, TRAFFIC AREAS, EQUIPMENT,FEED MILL OWNED BY WRIGHT COUNTY EGG – SUPPLIED ALSO HILLANDALE11 SAMPLES YIELDED SAME ORGANISM

POSITIVE SAMPLE ALSO FROM EGG WASHING FACILITY – HILLANDALE

VOLUNTARY RECALL BY BOTH COMPANIES

TECHNOLOGY AIDING NEW AGENTS EMERGE/SPREAD

FEEDING ANIMAL PRODUCTS TO ANIMALS – BONE MEALTRANSMISSABLE SPONGIFORM ENCEPHALITISMAD COW DISEASE

SUBURBAN DEVELOPMENT – NEW ENGLAND –DEER PREDATORS/HUNTERS ELIMINATEDDEER AND DEER TICKS FLUORISH – LYME DISEASE

BLOOD TRANSFUSIONS/TRANSPLANTS – HIV AND HEPATITIS C“BEFORE TESTING”

LIVING WITH DUCKS, BIRDS, PIGS – INFLUENZA ANTIGENIC SHIFTSPRODUCTION OF NEW VARIANTS TO WHICH PEOPLE NOTIMMUNE

COMMERCIAL MEAT PACKING – GROUND MEAT, HAMBURGER PATTIESE. COLI O157:H7 – ENTEROHEMORRHAGIC STRAIN - HUS