COMMUNICABLE DISEASE

• Communicable Disease


  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
• Communicable Diseases are Primary Cause of Mortality Gap between Rich and Poor Countries
• Non-communicable diseases account for 59% of all deaths worldwide – estimated to rise from 28m in 1990 to 50m in 2020
• Communicable Diseases that account for about 60% of deaths


  • HIV/AIDS
  • Malaria
  • Tuberculosis
  • Measles
  • Diarrheal disease
  • Acute respiratory infection
• 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)
• All contagious diseases are infectious, but not all communicable diseases are contagious
• Both infectious and contagious diseases are communicable
• Examples of communicable diseases


  • herpes, malaria, mumps, HIV/AIDS, influenza, chicken pox, ringworm, and whooping cough
• Cancer is not a communicable disease
• Carrier


  An individual who harbors the organism and is capable of transmitting it to a susceptible host without showing manifestations of the disease
• Contact


  Any person or animal who is in close association with an infected person, animal, or freshly soiled material
• Types of Diseases based on Occurrence


  • Sporadic Disease
  • Endemic Disease
  • Epidemic Disease
  • Pandemic Disease
• Sporadic Disease


  Disease that occurs only occasionally & irregularly with no specific pattern
• Endemic Disease


  Disease that is constantly present in a population, country or community
• 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
• Pandemic Disease


  Epidemic disease that occurs worldwide
• Types of Diseases based on Severity or Duration


  • Acute Disease
  • Chronic Disease
  • Latent Disease
• Acute Disease


  Develops rapidly (rapid onset) but lasts only a short time
• Chronic Disease


  Develops more slowly (insidious onset); disease likely to be continual or recurrent for long periods
• Latent Disease


  Causative agent remains inactive for a time but then becomes active to produce symptoms of the disease
• Types of Infections based on State of Host Resistance

  • Primary Infection
  • Secondary Infection
  • Subclinical (Inapparent Infection)
• Primary Infection


  Acute infection that causes the initial illness
• Secondary Infection


  One caused by an opportunistic pathogen after primary infection has weakened the body's defenses
• Subclinical (Inapparent Infection)


  Does not cause any noticeable illness
• Symptoms


  Subjective evidence of disease that is experienced or perceived; subjective changes in body function noted by patient but not apparent to an observer
• Signs


  Objective evidence of a disease the physician can observe and measure
• Syndrome


  A specific group of signs and symptoms that accompany a particular disease
• Incidence


  The number of people in a population who develop a disease during a particular time period
• Prevalence


  The number of people in a population who develop a disease, regardless of when it appeared; refers to both old and new cases
• Stages of Disease


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


  Time interval between the initial infection and the 1st appearance of any symptoms; patient is not yet aware of the disease
• Prodromal Period


  Early, mild appearance of symptoms of the disease
• Period of Illness


  Time of greatest symptomatic experience (patient is sick); overt symptoms of disease; WBC may increase or decrease; can result in death if immune response or medical intervention fails; communicable diseases are most easily transmitted during this phase
• Period of Decline


  Symptoms subside; pathogen replication is brought under control; vulnerable to secondary infection
• Period of Convalescence


  Replication of pathogenic organisms is stopped; regains strength and the body returns to its pre-diseased state; recovery has occurred
• Conditions that Affect Infection Development

  • Pathogenicity
  • Infective dose
  • Virulence and Invasiveness
  • Organism specificity
  • Resistance of the host
  • Immunity of the host
• Pathogenicity


  Ability to cause disease
• Infective dose


  Sufficient number of microorganisms needed to initiate infection
• Virulence and Invasiveness


  Disease severity and ability to enter and move through tissue