PART 1FUNDAMENTAL CONCEPTS IN PUBLIC HEALTH AND TROPICAL MEDICINE

LEARNING OBJECTIVES

1. Explain environmental health engineering aspect in public health and tropical medicine

2. Identify and describe dissemination of infectious disease related to water

WHAT IS PUBLIC HEALTH?

QUESTION: WHAT’S AN EPIDEMIOLOGIST?

a) A disease detectiveb) A skin doctorc) A scientist who studies the epicenter of disaster

sitesd) A scientist who studies epiphyte plants, such as

orchids or ferns

PUBLIC HEALTH ‘POLICE POWERS”

Inspections & closures Licensing & discipline of health professionals

& facilities Quarantine & isolation Vaccination, testing and treatment

requirement Seizure, embargo and impounding of unsafe

substances

PUBLIC HEALTH CONCEPT

Important major areas of public health: Health Services Epidemiology Social/Behavioral Science Environmental Health Biostatistics

PUBLIC HEALTH CONCEPT

Important major areas of public health: Health Services

Deals with diagnose & treatment of diseases Epidemiology

Study the causes of illness and distribution of disease in populations.

The science behind public health – study disease control & prevention.

Social/Behavioral Science Deals with human psychology, economics, history,

and anthropology. Focus to describe, understand, predict, and change the public's health

PUBLIC HEALTH CONCEPT Important major areas of public health:

Health Services Epidemiology Social/Behavioral Science Environmental Health

Deals with all environmental aspects (physical, chemical & biological) that impact human health. Involve assessment & control of these environmental factors to prevent disease & improve health

Biostatistics Application of statistic in area of biology via data

collection, analysis and interpretation. applied in public health including epidemiology,

health services research, nutrition, and environmental health

MAJOR TYPES OF PUBLIC HEALTH ACTIVITIES

Surveillance Outbreak investigation Reference diagnosis and consultation Research (bench-to-field-to-prevention) Technical assistance & training (lab & epi) Initiate & support implementation projects Health policy and Health communication [Philosophically founded on Epidemiology]

PUBLIC HEALTH SURVEILLANCE

Definition: The ongoing systematic collection, analysis, interpretation, and dissemination of health data = Information for Action!

Detect changes in disease occurrence and distribution

Detect changes in agent or host factors Detect changes in health care practices Follow trends and patterns of disease

TYPES OF SURVEILLANCE

• Passive Surveillance: Reports are sent to the health department

based on known rules and regulations • Enhanced Passive Surveillance:

The health department distributes information on a particular disease and asks for reports

• Active Surveillance: The health department calls or visits a

location to collect reports • Sentinel Surveillance:

A pre-selected sample of potential data sources submit information

SURVEILLANCE SYSTEM Hospital syndromic

surveillance Syndromes Diagnostic tests Bed and ventilator

availability Prescription

pharmaceutical stocks/usage

School surveillance Absenteeism Syndromes

Reportable disease surveillance

Environmental surveillance

24/7 phone duty Death surveillance

Pneumonia and influenza

Unusual deaths Death certificates

OTC pharmaceutical surveillance

EMS surveillance ELCIDS food-borne

disease surveillance

PUBLIC HEALTH VS. MEDICAL CARE

The concept of Public Health differs from the concept of individual medical care, and the

skills are very often different

Public Health deals with populations, prevention and policy, and includes research on all of these.

Public Health often involves the treatment of individual patients, but that is NOT its focus, but rather populations at risk

OUTBREAKS/EPIDEMICS

Definition: The occurrence of more cases of disease than is expected in a given area over a particular period of time.

The term epidemic often implies a larger number of cases over a wide geographic area

STEPS OF AN OUTBREAK INVESTIGATION1. Prepare for field work2. Establish the existence of an outbreak3. Verify the diagnosis4. Define and identify cases

1. Establish a case definition2. Identify and count cases

5. Perform descriptive epidemiology6. Develop hypotheses7. Evaluate hypotheses8. Reconsider/refine hypotheses and conduct

additional studies9. Implement control and prevention measures10. Communicate findings

GOALS OF AN OUTBREAK INVESTIGATION Describe the outbreak:

person, place, & time Determine disease

characteristics Specific agent Pathogenicity Incubation period Communicability

Identify modes of transmission Person-to-person Airborne Common source (food

or water) Zoonotic Vectorborne

Identify additional cases and contacts

Identify the source of infection

Interrupt disease transmission—present and future

TYPES OF OUTBREAKS

• Common source: everyone’s exposed to the same thing Point source: the exposure occurs all at once Intermittent or continuous: the exposure continues

over a period in time

Propagated: disease spreads gradually from person to person

Mixed: common source + person-to-person spread

• Other: zoonotic or vector-borne diseases

PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC

Control directed against the reservoir-animal, insect reservoir can be effectively control by eliminate them

PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC

Control directed against transmission of the pathogen:-

if via water/food, then public health procedure can be instituted to prevent contamination or destroy the pathogen in the vehicles.

Water purification help to reduce incidence of typhoid fever, pasteurized milk reduced bovine TB.

Devise food protection law to prevent enteric pathogen to human.

Respiratory transmission is difficult to prevent, wear mask, but this is not effective method as it’s voluntary measure.

PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC

Vaccination-tetanus, small pox, diphtheria, whooping cough, polio myelitis have been eliminated.

Adult inadequately immunised against childhood disease- low titre of Antibodies as immunity gradually disappear with age., so tetanus vaccine to be given every 10yr

PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC

Quarantine- involve limitation of freedom of movement of individual with active infection to prevent spread of disease

PUBLIC HEALTH MEASURE TO CONTROL EPIDEMIC

International agreement, 6 diseases are quarantinable: smallpox cholera typhoid fever plague yellow fever relapsing fever

Do you know these public

health workers?

PART2 : TROPICAL MEDICINE

Branch of medicine deal with unique problems (difficult to control & widespread)

in tropic & subtropic region. Many infections & infestation are classified

as “tropical disease” Used to be endemic in temperate/ cold weather

countries Many can be controlled & eliminated due to

improvement in housing, diet, sanitization & personal hygiene.

WHAT IS DISEASE?

•Disease (due to an infectious agent) is what may happen while your immune response tries to control an infection;

•Disease may be the final outcome if your immune system either fails, or over reacts.

•Infection does not necessarily equal disease

•Infectious disease: disease caused by replicating agent transmissible to human from other person, animal or environment

DISEASE

TERMINOLOGY

Prevalence Proportion (%) of diseased individual in a

population at any one time

Incidence Number of disease individual in a population at

risk

Epidemic Disease when occur in an unusually high number

in a community at the same time

Pandemic Widely distributed epidemic

Endemic Disease that is constantly present in a population,

usually at low incidence Pathogen may no be highly virulent Majority of people is immune Though, few individual may suffer and remain

reservoir for the infection

Outbreak Disease occur when a number of cases observed

ina relatively short time

Mortality Incidence of death

Morbidity Incidence of disease in populations and

include both fatal and nonfatal diseases. Statistically more precise to tell the health of

a population compare to mortality- as major cause of illness is quite different than a major cause of death.

EPIDEMIOLOGIC TERMS WE NEED TO KNOW

Incidence of infection Rate of infection (# new cases/year)

Prevalence of infection Proportion of population infected (%)

Intensity of infection Level of infection (# worms/patient) Severity of infection (morbidity/mortality)

Infectious disease Surveillance Systematic collection, analysis and use of data

on a given infectious disease

STAGES OF DISEASEIn term of clinical symptom, typical course of disease can be

divided into 6 stages:

1. Infection – organism lodged in the host2. Incubation period- time of infection and appearance of

symptoms. Length can be short/long depends on inoculum size, virulence of pathogen, resistance of host and distance from entrance site to the focus infection site

3. Prodromal period-a short period where 1st symptoms such as headache and feeling of illness appear

4. Acute period- disease at its height, with overt symptoms such as fever and chills

5. Decline period- symptom is subsiding, temperature falls, followed by intense sweating and feeling of well-being

6. Convalescent period- patient regains strength and return to normal.

During later stage of infection cycle, immune mechanism of the host becomes increasingly important. Recovery is normally due to these immune mechanism.

CAUSE OF DEATH WORLDWIDE

LEADING INFECTIOUS KILLERS WORLDWIDE

LEADING CAUSE OF DEATH

Health burden to nation

DEATH DUE TO DISEASE (USA DATA)

DEATH DUE TO WHOOPING COUGH (UK DATA)

EMERGING INFECTIOUS DISEASE

1.SARS

2. West Nile disease

3. Variant CJD disease

4. Monkey pox

5. Ebola and Marburg viruses

6. Dengue

7. Influenza H5/N1 (?)

8. Hanta virus

9. E. Coli O157:H7

10. Antibiotic-resistant Pneumococci S.aureus (MRSA) Gonococci Salmonella

11. Cryptosporidium

12. Anthrax

13.Spanish flu

14. Dengue & DHF

EMERGING INFECTIOUS DISEASE (AIDS-RELATED)

1. Pneumocystis carinii pneumonia

2. Tuberculosis

3. Mycobacterium-avium complex

4. Kaposi’s sarcoma (HHV-8)

5. HSV-2

6. Cryptosporidium

7. Microsporidium

8. Cryptococcus neoformans

9. Penicillium marneffei

10. Disseminated salmonella

11. Bacillary angiomatosis (Bartonella henselae)

12. HPV

FACTORS LEADING TO EMERGING OF INFECTIOUS DISEASE AIDS Population growth Speed and ease of

travel Dam building Global climate

change Increased antibiotic

use for humans and animals

Encroachment of human populations on forest habitats

Industrial commercial agriculture

War and social disruption

Relocation of animals

Growth of daycare Aging of the

population Human-animal

contact

DISEASE RESERVOIRS

Reservoir-sites at which viable infectious agent remain alive and from which infection of individuals may occur.

LIST OF HUMAN DISEASE AND ITS RESERVOIR:

• Anthrax – cattle, swine, goat, horse, sheep• Salmonellosis-poultry, egg, water polluted with

sewage• Botulism- soil, contaminated food• Giardiasis-beaver, marmot, water polluted with

animal feces• Malaria-Anopheles mosquito• Plague-wild rodent• Psittacosis-parrot, pigeon, birds• Rabies-wild & domestic carnivor• Respiratory disease- human carrier• Syphilis, goinorrhea, AIDS, STD- human• Tetanus- soil, intestine• Tuberculosis-human, dairy cattle• Typhoid fever -human

Some pathogens are saprophytic- ie live on dead matter. eg. Clostridium tetani in soil

For epidemiologist- interest in pathogen live on living matter

List of human disease and its reservoir

Example of how epidemiological research is performed- Epidemiology of AIDS

TRANSMISSION

Involves 3 stages: escape from host travel entry into a new host

CARRIERS infected individual not showing obvious sign of clinical

disease. Potential cause of infection to others Acute carrier- individual in the incubation period of

disease, then follow by development of the infection Chronic carrier-individual who had a clinical disease

and recovered, or may have subclinical infection that remained in apparent throughout.

Identify carrier by X-ray, immune test, cultural 2 diseases with significant carrier- typhoid fever and

TB (usually food handler) eg. Typhoid Mary in early 1990s

MODES OF INFECTIOUS DISEASE TRANSMISSIONEpidemiologist follows the incidence of disease by

correlate geographical, seasonal and age-group distribution of a disease with possible modes of transmission.

If disease is limited to a restricted geographical location- it may suggest vector, eg. Tropical region, malaria via mosquito vector

If disease is limited by seasonal- often indicate mode of tramsmission eg. Measles, chickenpox for school children and close contact

Age distribution- important for statistic to eliminate particular routes of transmission

Different pathogen, have different mode of transmission- usually related to the habitat of the organism in the body

Eg. Respiratory pathogen is usually airborne, intestinal pathogen usually, waterborne/ food borne

DIRECT HOST-TO –HOST TRANSMISSION

infected host transmit disease to a susceptible host route can be respiratory (cold, flu), direct contact

(syphilis, gonorrhea), skin direct contact (staphyloccus causes boil, pimples) or fungi (ringworm)

INDIRECT HOST-TO-HOST TRANSMISSION

occur by living/ inanimate means living agent transmit disease is called vector- usually

anthropods (insect, mites or fleas) or vertebrates (dog, cats)

Anthropods only carrier of agent from 1 host to another , not a host for the disease- via biting

Some pathogen replicate inside anthropods (this consider an alternate host) and build up inoculum

Inanimate agent- bedding, toys, books, surgical equipment- which come in contact with people can also transmit disease. This inanimate object is refer to fomites

Food and water are referred to as disease vehicles.

CAUSATIVE AGENTS OF DISEASE

biological- bacteria , virus, protozoa, helmith and fungi, prion

chemical- pesticide, petroleum product, cleansing agent physical- sun UV, X-ray equipment, too little of something- lack of Vit. D cause rickets, lack of

niacin cause kwashiorkor too much of something- excessive food or water can be

fatal, excess CO2 in respiratory can cause fatal hereditary- haemophilia, baldness, poor eyesight stress-emotional disorder, stroke, heart attack disease of unknown cause- many die due to environmental

pollutant working synergistically with other factors. Eg. cancer

CAUSATIVE AGENTS OF DISEASE

Biological, Chemical and Physical cause of disease are spread through air, water, food, insect, fomites (fork, doorknob etc) and animal.

In Environmental health, many programmes address the need to control the causative agent while it is in the environment before it get into the public and cause disease.

PORTAL OF ENTRY

Skin- epidermis provide defence vs. pathogen entry, if cut occur, pathogen may allow in

reproductive organ- penis, uterus and ovaries –require body contact, STD- prevention by prophylactics or abstention from sex

respiratory tract (nose, bronchi, aveoli)- TB, pneumonia, strep, human nose has hair to filter pathogen, cilia, mucus to prevent it

Digestive tract- mouth, aesophagus, stomach, small intestine and large intestine- HCL secreted in stomach kill some germ, bile has an antiseptic power because eof its high pH

HUMAN DEFENCE AGAINST DISEASE

1st line of defence (ENVIRONMENTAL MANAGEMENT)- prevention. Apply technology and art of science to control causative agent of disease in environment before it gets to human. This use the environmental health element

2nd line of defence (PUBLIC HEALTH & PREVENTIVE MEDICINE)-based on human body adaptation to prevent agent of disease. This include skin, mucous membrane, cilia, tears- so, proper nutrition, good personal health practise, routine check up

3rd line of defence (PUBLIC HEALTH &PREVENTION MEDICINE)-if the 2nd defence are not sufficient to prevent the entrance of pathogens, then use immunity (active and passive) and phagocytosis (natural- leukocytes destroy pathogen in blood).

4th line of defence (CURATIVE MEDICINE)- when sick, need surgery-medication.

THE 1ST LINE OF DEFENCE VS. DISEASE Water quality

management Human waste

disposal Solid and hazardous

waste management Rodent control Insect control Milk sanitation Food quality

management Occupational health

practice – assure healthy and safety of worker

International travel sanitation

Air pollution control

Water pollution control Environment safety &

accident prevention Noise control Housing hygiene Radiological health

control Recreational sanitation Institutional

environmental management- prevent nosocomial infection

Land use management Product safety &

consumer protection Environmental

planning

2nd LINE of DEFENCE vs. DISEASE:

Host defenses: physical, chemical, anatomical barriers:

HPR173rd LINE OF DEFENCE:

nonspecific defenses (passive defenses; innate immunity) – respond to any invader • natural barriers, antimicrobial compounds• phagocytes (neutrophils or polymorphonuclear leukocytes, PMNs)• complement • natural killer cells (NK cells)

specific defenses (adaptive immunity) – respond to a specific invader• cell-mediated – cytotoxic T cells, activated macrophages• humoral - antibodies

cytokines, chemokines – small proteins; coordinate, modulate

Host immunity: the ability of higher organisms to resist infection

blood and lymph systems

extravascation:

HPR23

bacteria

phagocytosisphagocytosis::

PMNPMN

nucleus

lysosomebacteria are engulfed in phagosome of PMN

phagosomefusion of phagosome and lysosome

degradation of bacteria within phagolysosomerelease of bacterial

fragments to external environment

HPR24

• several pattern recognition molecules (PRMs) on PMN membrane (aka Toll-like receptors (TLRs))

• recognize a pathogen-associated molecular pattern (PAMP)

• e.g., TLR-4 recognizes bacterial LPS

Innate host defenses:

• natural host resistance – some organisms more sensitive to infection by given pathogen than others

• age – very young, very old individuals are most susceptible

• stress – fatigue, exercise, dehydration, large climate changes, stress-related hormone release, suppression of inflammation; predispose to infection

• diet – alteration may influence normal microbiota, decrease resistance, alter susceptibility

• physical, chemical, anatomical barriers – may prevent successful infection when integrity is intact

• tissue specificity – pathogen must contact environment suited to its needs, for successful infection

compromised host: one or more resistance mechanisms inactive; susceptibility increased• suppressed – e.g., drug therapy-induced versus compromised – e.g., AIDS

3rd LINE OF DEFENCE (continue)

ZOONOSES disease that occur primarily in animal, but

occasionally transmitted to human. Since public health for animal is less, infection rate for

these disease in animal is very high. Transmission is animal to animal. Occasionally animal to human. Thus, to control

zoonosis in human is not good approach to eradicate it from animal reservoir.

Success case for zoonosis control are bovine TB and brucelosis via pasterisation of milk.

Some have more complex life cycle. Eg. Protozoa (malaria) and metazoans(tapeworms). So, contol in human or in the alternative animal host.

INFECTIOUS DISEASE RELATED TO ANIMAL CONTACT

NOSOCOMIAL INFECTION

Hospital acquired infections Cross infection from patient or hospital personnel and vice versa

present a constant hazard Hospital are hazardous because

1. many patients are weakened resistance to disease 2. reservoir for highly virulent pathogen3. Crowding of wards4. much movement of hospital personnel from patient to patient5. hospital procedure such as catheterisation, hypodermic

injection, spinal puncture, removal of tissue/fluid/biopsy carry risk of introducing pathogen to patient

6. In maternity ward, infant immune system usually susceptible to infection

7. surgical procedure is major hazard, body exposed to source of contamination

8. drug for immunosuppressant (organ transplant patient) increase susceptibility to infection

9. use antibiotic to control infection carry risk of resistant strain (MRSA)

HOSPITAL PATHOGEN E.coli as most causes for Urinary tract infection, others are

yeast Candida albican, Psedomonas aeruginosa, enterococcus

Staphylococcus aureus - associated with skin, surgical, and lower respiratory tract- problem for newborn baby

S.aureus habitat is in nasal passage – as normal flora. So, in healthy personnel show no disease, but once infected the susceptible patients may cause serious infection

Pseudomonas aeruginosa- causing infection of lower respiratory and urinary tract. Also cause infection in burn patients (where patient loss barrier to skin infection) It is drug resistant, so difficult to treat.

WHAT ARE THESCARIEST INFECTIOUSTHREATS?

Bioterrorism (anthrax; sm’pox; etc.

Pandemics (influenza; plague;..)

Can you say: BIRD FLU ???

Nosocomial Infections

Ebola; SARS; Lyme; Hanta; Cryptosp; Cyclospora; E. coli 0157/H7

POSSIBLE AGENTS OF BIOTERRORISM

POTENTIAL BIOTERRORISM AGENTS

Category A: (anthrax, botulism, plague, smallpox, tularemia, VHFs) can be easily disseminated or transmitted from

person to person; result in high mortality rates and have the

potential for major public health impact; might cause public panic and social disruption;

and require special action for public health

preparedness

POTENTIAL BIOTERRORISM AGENTS

Category B: (ricin, food/water threats, brucellosis, Q fever, etc.) are moderately easy to disseminate; result in moderate morbidity rates and low

mortality rates; and require specific enhancements of CDC's

diagnostic capacity and enhanced disease surveillance.

POTENTIAL BIOTERRORISM AGENTS

Category C: (emerging infections like Nipah virus and hantavirus) availability; ease of production and dissemination; and potential for high morbidity and mortality rates

and major health impact.

CHARACTERISTICS OF BIOTERRORISM Presentation of a rare and serious disease Presentation of rare and serious symptoms Large number of people seeking care for

nonspecific symptoms Unexpected rapidly increasing disease

incidence Disease clusters w/a common source of

infection Endemic disease rapidly emerging at an

uncharacteristic time or in an unusual pattern

Low attack rates for people who stay indoors Sudden increase in mortality