EpidemiologyEpidemiology• Study of the distribution and Study of the distribution and

causes of disease in populationscauses of disease in populations– how many people or animals have a how many people or animals have a

diseasedisease– the outcome of the disease the outcome of the disease

(recovery, death, disability, etc.)(recovery, death, disability, etc.)– the factors that influence the the factors that influence the

distribution and outcome of the distribution and outcome of the diseasedisease

Epidemilogical TriadEpidemilogical TriadEnvironmentEnvironment

  VectorVector  

  

  

AgentAgent

HostHost

Types of HazardsTypes of Hazards•Biological HazardsBiological Hazards

–These are living organisms or their products that are harmful to humans

Biological HazardsBiological Hazards•Water-borne diseasesWater-borne diseases

– Transmitted in drinking waterTransmitted in drinking water•Disease organisms shed into Disease organisms shed into water in feceswater in feces

•Can produce illness in those who Can produce illness in those who consume untreated, contaminated consume untreated, contaminated waterwater

Biological HazardsBiological Hazards•Water-borne diseasesWater-borne diseases

– municipal water treatment municipal water treatment facilities are usually able to facilities are usually able to purify water purify water •removing these agents by removing these agents by filtrationfiltration

•killing them by disinfectionkilling them by disinfection

Biological HazardsBiological Hazards•Water-borne diseasesWater-borne diseases

– Examples Examples •Polio virusPolio virus•Hepatitis A virusHepatitis A virus•SalmonellaSalmonella•CholeraCholera

Waterborne Waterborne BacteriaBacteria

Escherichia coliBarbara E. Moore, Ph.D., Department of Biology, University of Texas at San Antonio

• Disease symptoms usually are Disease symptoms usually are explosive emissions from either explosive emissions from either end of the digestive tractend of the digestive tract

Waterborne Waterborne ProtozoansProtozoans

Giardia sp.**P. Darben

Barbara E. Moore, Ph.D., Department of Biology, University of Texas at San Antonio

• Disease symptoms are usually Disease symptoms are usually explosive emissions from either explosive emissions from either end of the digestive tractend of the digestive tract

Waterborne Waterborne Human Human VirusesViruses

Hepatitis A virus Hepatitis E virus

Norwalk virus* Rotavirus**F. Williams

Barbara E. Moore, Ph.D., Department of Biology, University of Texas at San Antonio

Eradicating Eradicating DracunculiasisDracunculiasis

Water and Sanitation – Critical Elements in Development - Mike Lee CSU @ HaywardWater and Sanitation – Critical Elements in Development - Mike Lee CSU @ Hayward

http://www.youtube.com/watch?v=Qwk-THcjmlI

http://www.youtube.com/watch?v=omudJzeX4q0&feature=related

http://www.youtube.com/watch?v=8FYgQFSrZDE&feature=related

Biological HazardsBiological Hazards•Food–borne diseasesFood–borne diseases

– To protect against food-borne To protect against food-borne diseasedisease•local health departments local health departments

– inspect inspect »food service establishments food service establishments (restaurants) (restaurants)

»retail food outlets (supermarkets)retail food outlets (supermarkets)»processing plantsprocessing plants

–verify that foodverify that food»stored stored »handled properlyhandled properly

Biological HazardsBiological Hazards•Food-borne diseasesFood-borne diseases

– Examples Examples •SalmonellaSalmonella

–Eggs or undercooked chickenEggs or undercooked chicken–ReptilesReptiles

•Escherichia coli 0157:H7Escherichia coli 0157:H7–SpinachSpinach–Undercooked meatUndercooked meat

»Jack in the BoxJack in the Box

Biological HazardsBiological Hazards•Vector-borne diseasesVector-borne diseases

– Transmitted by insects, Transmitted by insects, other arthropods and other arthropods and other animals including other animals including humanshumans

– Improper environmental Improper environmental management can cause management can cause vector-borne disease vector-borne disease outbreaksoutbreaks

Biological HazardsBiological Hazards•Vector-borne diseasesVector-borne diseases

– Examples Examples •MosquitoesMosquitoes

–MalariaMalaria–West Nile VirusWest Nile Virus

•FleasFleas–Bubonic plague Bubonic plague

3. Mosquito injects Plasmodium sporozoites into human host

2. Plasmodium develops in mosquito

1. Female mosquito bites infected human, ingesting blood that contains Plasmodium gametocytes

4. Parasite invades blood cells, causing malaria and making infected person a new reservoir

Anopheles mosquito (vector)in aquatic breeding area

eggslarva

pupaadult

Fig. 16.10, p. 409

Areas in which malaria hasdisappeared, been eradicated,or never existed

Areas with limited risk

Areas where malariaTransmission occurs

Biological HazardsBiological Hazards•Vector-borne diseasesVector-borne diseases

– Examples Examples •HumansHumans

–SARSSARS–Tuberculosis Tuberculosis –HIVHIV–STDsSTDs

Deaths per100,000 people

<2.5

2.5-10

10-35

35-70

70-100

100+

Tuberculosis epidemic, kills about 2 million people a year.

Biological HazardsBiological Hazards•Vector-borne diseasesVector-borne diseases

– Greatest viral health Greatest viral health threat to human life are threat to human life are virulent flu strainvirulent flu strain•1918 Swine Flu1918 Swine Flu

–Killed 20 – 30 millionKilled 20 – 30 million•Today flu kills Today flu kills

–1 million per year worldwide1 million per year worldwide–20,000 in the U.S.20,000 in the U.S.

Spread of DiseasesSpread of Diseases• Increases international travelIncreases international travel• Hunger and malnutritionHunger and malnutrition• Accidental introduction of insect Accidental introduction of insect

vectorsvectors• FloodingFlooding

Reducing Spread of Reducing Spread of DiseasesDiseases

• Reduce poverty and malnutritionReduce poverty and malnutrition• Improve drinking waterImprove drinking water• Reduce unnecessary use of antibioticsReduce unnecessary use of antibiotics• Educate people on taking antibioticsEducate people on taking antibiotics• Reduce antibiotic use in livestockReduce antibiotic use in livestock• Careful hand washing by medical staffCareful hand washing by medical staff

Hazardous Hazardous ChemicalsChemicals

•Methods to determine threatMethods to determine threat– Case StudiesCase Studies

•MD with actual patient recordMD with actual patient record– EpidemiologyEpidemiology

•Health officials investigating case Health officials investigating case studies studies

–Laboratory InvestigationsLaboratory Investigations•Substances that are fatal to more Substances that are fatal to more than 50% of the test animals (LD50) than 50% of the test animals (LD50) at a given concentrationat a given concentration

ToxicityToxicityToxicity LD50 Lethal Dose Examples

Super < 0.01 less than 1 drop dioxin, botulism

Extreme <5 less than 7 drops heroin, nicotine

Very 5-50 7 drops to 1 tsp. morphine, codeine

Toxic 50-500 1 tsp. DDT, H2SO4, Caffeine

Moderate 500-5K 1 oz.-1 pt. aspirin, wood alcohol

Slightly 5K-15K 1 pt. ethyl alcohol, soaps

Non-Toxic >15K >1qt. water, table sugar

(LD50 measured in mg/kg of body weight)

Dose-Response Dose-Response CurvesCurves

Nonlineardose-response

Lineardose-response

Thresholdlevel

Eff

ect

Eff

ect

DoseDose

Nonlineardose-response

Lineardose-response

No thresholdNo threshold

Eff

ect

Eff

ect

ThresholdThreshold

DoseDose

Fig. 16.6, p. 401

Chemical HazardsChemical Hazards•Hazardous ChemicalsHazardous Chemicals

•MutagensMutagens– Chemicals (and ionizing Chemicals (and ionizing

radiation) that changes DNA or radiation) that changes DNA or RNA in cellsRNA in cells

Chemical HazardsChemical Hazards•Hazardous ChemicalsHazardous Chemicals•MutagensMutagens

–TeratogensTeratogens•Chemicals, radiation, or viruses Chemicals, radiation, or viruses that cause birth defects while the that cause birth defects while the human embryo is gestating, human embryo is gestating, especially in the first three monthsespecially in the first three months

TeratogensTeratogens•Examples:Examples:

– RubellaRubella– Mercury in waterMercury in water– Fetal alcohol syndromeFetal alcohol syndrome– Crack found in babiesCrack found in babies– MethamphetamineMethamphetamine

Chemical HazardsChemical Hazards•Hazardous ChemicalsHazardous Chemicals•MutagensMutagens

– TeratogensTeratogens

–CarcinogensCarcinogens

CarcinogensCarcinogens•Causative agentsCausative agents

– Chemicals – Tobacco smokeChemicals – Tobacco smoke– Radiation – Pilots and cosmic Radiation – Pilots and cosmic

radiationradiation– Viruses – HPV and cervical cancerViruses – HPV and cervical cancer

•Promote growth of malignant Promote growth of malignant tumorstumors

CarcinogensCarcinogens•Latent PeriodLatent Period

– Long time lapse between Long time lapse between exposureexposure•SmokingSmoking•EatingEating•Lifestyle choices – laying in sunLifestyle choices – laying in sun

– SymptomsSymptoms•Lung cancerLung cancer•MelanomaMelanoma

Chemical HazardsChemical Hazards•Hazardous ChemicalsHazardous Chemicals•MutagensMutagens

– TeratogensTeratogens– CarcinogensCarcinogens

•Hormonally Active Hormonally Active AgentsAgents

Hormonally Active Hormonally Active AgentsAgents

•Estrogen-like chemicalsEstrogen-like chemicals– Alter developmentAlter development

•Early pubescenceEarly pubescence•Low sperm countLow sperm count•Runts in wildlifeRunts in wildlife

– Examples of hormone mimicsExamples of hormone mimics•BPABPA•Organophosphates pesticidesOrganophosphates pesticides•Industrial solventsIndustrial solvents

Precautionary Precautionary PrinciplePrinciple

•BioaccumulationBioaccumulation–An increase in An increase in concentration of a concentration of a chemicals in specific chemicals in specific organs or tissues in organs or tissues in organisms organisms

Precautionary Precautionary PrinciplePrinciple

•BiomagnificationBiomagnification– Increase in concentration in Increase in concentration in organismsorganisms•DDTDDT•PCBPCB•Slowly degradable, fat-soluble Slowly degradable, fat-soluble chemicalschemicals

– At successively higher trophic At successively higher trophic levels of food chains or in fatty levels of food chains or in fatty tissuetissue

DDT in fish-eatingDDT in fish-eatingbirds (ospreys)birds (ospreys)

25 ppm25 ppm

DDT in largeDDT in largefish (needle fish)fish (needle fish)2 ppm2 ppm

DDT in smallDDT in smallfish (minnows)fish (minnows)0.5 ppm0.5 ppm

DDT inDDT inzooplanktonzooplankton0.04 ppm0.04 ppm

DDT in waterDDT in water0.000003 ppm,0.000003 ppm,Or 3 ppmOr 3 ppm