
There have been several diseases that have spread across the world killing many

In the middle ages it was the Bubonic or
Black Plague

In 1981 it was HIV


An area of investigation that deals with factors that influence the frequency and distribution of diseases

Find ways to control and prevent the outbreak of disease

Look for the source of transmission

Reporting of the control of the disease

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Incidence or Prevalence

The number of new cases seen in a specific time period

Morbidity Rate
 The number of new cases per 10,000 in the population per year

Mortality Rate
 Refers to the number of individuals that died as a result of a specific disease in a specific time period

Endemic, Epidemic, Pandemic and
Sporadic Disease Patterns

Endemic Disease

A disease that is constantly present in the population of a particular geographic area, but involves relative few individuals
 Severity of the disease is low

Does not present as a major public health problem

Tuberculosis, mumps, the STD chancroid and gonorrhea

Endemic, Epidemic, Pandemic and
Sporadic Disease Patterns

Epidemic

An unusual occurrence of a disease involving large segments of a population for a limited period of time

An endemic disease can develop into an epidemic if a harmful form of the pathogen appears

Influenza and measles are good examples
 Genital Herpes and Genital Warps are in epidemic proportions

Endemic, Epidemic, Pandemic and
Sporadic Disease Patterns

Pandemic

A series of epidemics affecting several countries, or even major portions of the world
 Influenza of 1918-
1919

HIV and AIDs are following a similar pattern

Endemic, Epidemic, Pandemic and
Sporadic Disease Patterns

Sporadic Diseases

Are uncommon, occur irregularly and affect only a relatively few persons
 Diptheria
 Whooping Cough – although this is on the rise in the US

Transmission Factors include:

Sources and reservoirs of disease agents

Portals by which the agents leave and enter the body

The mechanisms or means of transmission

Factors in the Spread of Infectious
Diseases

Reservoirs of Infection

A host or local environment that supports the survival and multiplication of pathogens is referred to as a reservoir of infection

Living reservoirs include infected humans and other animals

Nonliving reservoirs include air, food, soil, water, eating utensils and toothbrushes

Provides the disease agent a suitable environment to survive for prolonged periods

Factors in the Spread of Infectious
Diseases

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
Carrier

Individuals who harbor pathogens transmissible to others
Healthy Carrier

A carrier with no apparent ill effects
Incubatory Carrier

The individual who is in an incubating state, undergoing the initial stages of a disease without exhibiting symptoms
Intermittent Carrier

Periodically releases disease agents
Convalescent Carrier

Serves as a source of pathogens during the recovery period

How do Pathogens Get Into and Out of the Body?


Portals of Entry

Pathogens enter the body through a small number or routes
 Skin
 Respiratory system
 Gastrointestinal system

Genitourinary system
 Wounds
 Animal bites
Particular pathogens are generally restricted to a specific portal of entry


Infectious Dose

The number of pathogens needed to initiate a disease process
 May be as low of one organism or may need hundreds of thousands

HIV infection requires large doses of disease agent

The pathogen must overcome the hosts defenses in order to enter

If it cannot overcome the defenses the pathogen dies


The site at which the organisms leave the body

Pathogens are typically discharged with body fluids and wastes.

Respiratory pathogens exit by
 Coughing

Sneezing

Speaking

STDs such as gonorrhea and HIV discharge through semen and vaginal secretions


Transmission may occur by:





Direct contact with infected person or carrier
Indirect contact with nonliving objects, or food or water contaminated by infected individuals
Inhalation of airborne dust or droplets of saliva, or other body fluids containing pathogens
Injection of body fluids containing disease agents
Insects and related forms carrying pathogens


Direct Contact

Refers to the transmission of pathogens from person to person through close personal association





Coughing
Sneezing
Handshaking
Kissing
Sneezing


Indirect Contact

Infectious agents are carried form one individual to another on contaminated, living or nonliving objects
Fomites

Contaminated nonliving objects other than food and water

Hypodermic needle


Toothbrush
Eating utensils


Transmission where situations involving the physical carrying of pathogens on or within contaminated materials such as food, water or insects

Five F’s

Food

Fingers
 Flies
 Feces
 Fomites




Vector

Forms of life that transmit disease to humans




Flies
Ticks
Cockroaches
Mosquitoes
Mechanical Vectors

Transmitters that carry infectious agents on their bodies and are not used by the agents for multiplication
Biological Vectors

Serves as reservoirs and are at times required by disease agents for their development



Ticks
Mosquitoes
There are no known STDs transmitted by arthropod vectors


A portion of the pathogen’s development occurs in the form of life that serves to transmit the disease agent

Injection of blood

Blood products

Bites of warm-blooded animals

Arthropods

Malaria

Rabies

Hepatitis

HIV


Horizontal Transmission

Transfer of disease agents in the population by air, physical contact, food, water or vectors

Vertical Transmission

Transfer of infectious agents from parent to offspring by means of male and female sex cells or breast milk or during pregnancy
 Syphilis and HIV

General Approaches to the Control of
Contagious Diseases

Isolation and Quarantine

Prevents contact with the general population
 Minimizes the spread of the disease
 Protects infected individual from exposure to other diseases

Elimination of Vectors and Sources of Disease
Agents

Hand washing

Disinfectant

Insecticides


Vaccination for the prevention of diseases

Builds resistance to the disease

Large spread controversy today

The signs of certain sexually transmitted diseases
(STDs) such as syphilis and chlamydial infection are not always obvious
A.
B.
True
False

In general, STDs can be acquired through casual contact situations such as shaking hands.
A.
B.
True
False

Diagnostic tests are available for the detection of most STDs.
A.
B.
True
False

Most STDs are treatable if detected early.
A.
B.
True
False

Having an STD such as syphilis, chancroid, or genital wars can increase the possibility of human immunodeficiency (HIV) transmission.
A.
B.
True
False

The proper use of latex condoms during sexually related activities, while not foolproof, is effective in preventing STD transmission.
A.
B.
True
False

An infected mother can transmit certain STDs such as syphilis and HIV infection to her newborn.
A.
B.
True
False

With the exception of hepatitis B virus infection, no immunization (vaccines) are available for any STD.
A.
B.
True
False

The use of oil-based lubricants such as Crisco and
Vaseline can weaken condoms, making them useless as protection against STD transmission
A.
B.
True
False

Sexually transmitted diseases can spread by women as well as men.
A.
B.
True
False

An individual can acquire an STD by donating blood.
A.
B.
True
False

Sexually transmitted diseases such as syphilis and gonorrhea can be spread by kissing.
A.
B.
True
False