COMMUNICABLE DISEASE

• Communicable disease

  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 a primary cause of the mortality gap between rich and poor countries because of the resources like immunizations
• Non-communicable diseases account for 59% of all deaths worldwide, estimated to rise from 28m in 1990 to 50m in 2022
• Communicable diseases account for 41% of deaths, which is still not a good sign because they are preventable because of the immunizations
• 60% of deaths caused by communicable diseases can be attributed to

  • HIV/AIDS
  • Malaria
  • Tuberculosis
  • Measles/tigdas
  • Diarrheal Disease
  • Acute respiratory infection

  
• Examples of communicable diseases

  • herpes, malaria, and mumps
  • HIV/AIDS, influenza, chicken pox, ringworm, and whooping cough (pertussis)

  
• Communicable disease


  Any disease that spreads from one host to another, either directly or indirectly
• Contagious disease


  A disease that easily spreads directly from one host to another
• Infectious disease


  A disease that is not transmitted but requires a direct inoculation of pathogenic agents (microbes). On the other hand, all contagious diseases are infectious
• Morbidity


  Common disease
• Mortality


  Cause of death; death
• Carrier


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


  Any person or animal who is in close association with an infected person, animal, or freshly soiled material (symptomatic)
• Classification of infectious disease

  • Sporadic disease
  • Endemic disease
  • Epidemic disease
  • Pandemic disease
• Sporadic disease


  A disease that occurs only occasionally and irregularly with no specific pattern (e.g. Botulism, Tetanus)
• Endemic disease


  Constantly present in a population, country, or immunity (e.g. Malaria)
• Epidemic disease


  Patient acquires the disease in a relatively short period of time; greater than normal number of cases in an area within a short period of time (e.g. Cholera, Typhoid)
• Pandemic disease


  An epidemic disease that occurs worldwide (e.g. HIV infection; SARS; COVID 19)
• Based on the severity or duration of the disease


  • Acute disease
  • Chronic disease
  • Latent disease
• Acute disease


  Develops rapidly (rapid onset) but lasts only a short time (e.g. Measles, mumps, influenza)
• Chronic disease


  Develops more slowly (insidious onset) disease likely to be continual or recurrent for long periods (e.g. Leprosy, TB)
• Latent disease


  The causative agent remains inactive for a time but then becomes active to produce symptoms of the disease (e.g. Shingles (zoster; from chicken pox), amoebiasis)
• Based on the 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 noded 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, referring 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/signs, when the 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 when the patient is sick, with overt signs/symptoms of disease, where WBC may increase or decrease, and can result in death if immune response or medical intervention fails. Communicable diseases are most easily transmitted during this phase.

  
• Period of decline


  Signs/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
  • Resistance of the host
  • Immunity of the host
• Pathogenicity


  Ability to cause disease
• Infective dose


  Sufficient number of microorganisms needed to initiate infection