Communicable Diseases I

• Communicable Diseases - is an illness due to an infectious agent or its toxic products which is easily transmitted or communicated directly or indirectly from one person or animal to another
• Contagious Disease - disease that easily spreads directly from one person to another
• Infectious Disease - disease not transmitted by ordinary contact but require a direct inoculation of pathogenic agents (microbes). On the other hand, all contagious diseases are infectious.
• Carrier – is an individual who harbors the organism and is capable of transmitting it to a susceptible host without showing manifestations of the disease.
• Contact -  is any person or animal who is in close association with an infected person, animal, or freshly soiled material
• Classification of Infectious Diseases:

  Based on Occurrence of Disease:

  • Sporadic Disease
  • Endemic Disease
  • Epidemic Disease
  • Pandemic Disease
• Classification of Infectious Diseases

  Based on Severity or Duration of Disease

  • Acute Disease
  • Chronic Disease
  • Latent Disease
• Classification of Infectious Diseases

  Based on State of Host Resistance:

  • Primary Infection
  • Secondary Infection
  • Subclinical/Inapparent Infection
• Based on Occurrence of Disease

  Sporadic Disease - disease that occurs only occasionally & irregularly with no specific pattern (tetanus, botulism)
• Based on Occurrence of Disease

  Endemic Disease - constantly present in a population, country or community (malaria)
• Based on Occurrence of Disease

  Epidemic Disease - = patient acquire the disease in a relatively short period of time ; greater than normal number of cases in an area  within a short period of time (cholera, typhoid)
• Based on Occurrence of Disease

  Pandemic Disease - epidemic disease that occurs worldwide (HIV infection; SARS; COVID-19)
• Based on Severity/Duration of Disease

  Acute Disease - develops rapidly (rapid onset) but lasts only a short time (measles, mumps, influenza)
• Based on Severity/Duration of Disease

  Chronic Disease - develops more slowly (insidious onset) disease likely to be continual or recurrent for long periods (tuberculosis, leprosy)
• Based on Severity/Duration of Disease

  Latent Disease - causative agent remains inactive for a time but then becomes active to produce symptoms of the disease (chicken pox > shingles)
• Based on State of Host Resistance

  Primary Infection - acute infection that causes the initial illness.
• Based on State of Host Resistance

  Secondary Infection - one caused by an opportunistic pathogen after primary infection has weakened the body’s defenses
• Based on State of Host Resistance

  Subclinical Infection - does not cause any noticeable illness
• Stages of Disease

  • Incubation Period
  • Prodromal Period
  • Period of Illness
  • Period of Decline
  • Period of Convalescence
• Stages of Disease

  Incubation Period - time interval between the initial infection and the 1st appearance of any s/sx
• Stages of Disease

  Prodromal Period - early, mild appearance of symptoms of the disease.
• Stages of Disease

  Period of Illness - •Time of greatest symptomatic experience (pt. is sick)• overt s/sx of disease •WBC may increase or decrease •Can result to death if immune response or medical intervention fails •Communicable disease are most easily transmitted during this phase
• Stages of Disease

  Period of Decline - s/sx subside and pathogen replication is brought under control and vulnerable to secondary infection
• Stages of Disease

  Period of Convalescence - Replication of pathogenic organisms is stopped regains strength and the body returns to its pre diseased state.
• Pathogenicity – ability to cause disease
• Chain of Infection

  • Source of Infection
  • Reservoir
  • Portal of exit
  • Mode of transmission
  • Portal of entry
  • Susceptible host
• Types of Carriers

  Passive Carrier - carry the pathogen without ever having had the disease. They are said to be asymptomatic. can also be uninfected but can transfer infectious agents from infected persons to uninfected ones by hand and instrument contact
• Types of Carrier

  Incubatory Carrier - a person who is capable of transmitting a pathogen during the incubation period of a particular infectious disease.
• Types of Carrier

  Convalescent Carrier - can harbor and can transmit a particular pathogen while recovering from an infectious disease
• Types of Carrier

  Active Carrier - completely recovered from the disease, but continue to harbor the pathogen indefinitely.
• Mode of Transmission

  Droplet Contact - occurs within 3 ft from source (from coughing, sneezing or talking to an infective person)
• Mode of Transmission

  Contact Transmission

  • Direct Transmission - immediate direct transfer of microorganism from person to person
• Mode of Transmission

  Contact Transmission

  : Indirect Transmission

  • by Vehicle route
  • Fomites
  • by Vector route
• Mode of Transmission

  Airborne Transmission

  • Droplet Nuclei - residue of evaporated droplets that remain suspended in air
• Infection Control: 1st line of Defense

  • First Line
  • Hand Hygiene
  • Handwashing
• IMMUNITY - is the condition of being secure against any particular disease, particularly the power which a living organism possesses to resist and overcome infection also the resistance that an individual has against disease
• Immune System - protection against infective or allergic diseases by a system of antibodies, immunoglobulins and related resistance factors.
• Antibody - a specific immune substance produced by the lymphocytes of the blood of tissue juices of man or animal in response to the introduction into the body of an antigen
• IMMUNOGLOBULINS

  • IgG - most prevalent antibody 80%, produced later in the immune response, only Ig that can cross placenta
  • IgA - found in colostrum, tears, saliva, sweat
  • IgM - principal antibody of blood, quickly produced in response to an antigen, responds to artificial immunization
  • IgE - responds to allergic reaction
  • IgD - unknown, antigen receptor, found in the surface of the cells
• Antigen - triggering agent of the immune system; foreign substance introduced into the body causing the body to produce antibodies