FACTORS IN THE SPREAD OF DISEASE

Spread of Diseases

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

Epidemiology

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

Patterns of Disease Occurrence 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

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

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

Portals of Exit

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

Mechanisms of Disease Transmission

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

Contact Transmission

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

Mechanical Transmission

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

Mechanical Transmission

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

Biological Transmission

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 and Vertical Transmission 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

Immunization

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 obviousA. TrueB. False

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

A. TrueB. False

Diagnostic tests are available for the detection of most STDs.

A. TrueB. False

Most STDs are treatable if detected early.

A. TrueB. False

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

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

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

A. TrueB. False

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

A. TrueB. False

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

A. TrueB. False

Sexually transmitted diseases can spread by women as well as men.

A. TrueB. False

An individual can acquire an STD by donating blood.

A. TrueB. False

Sexually transmitted diseases such as syphilis and gonorrhea can be spread by kissing.

A. TrueB. False