Infectious diseases

Nota:

• 1. caused by infectious agents (generate spontaneous/from air)

1. Definition
   1. Infectious disease

      Nota:

      • -disease caused by infectious agents(bacterium, virus, protozoan, fungus) -can be passed to other host
   2. Infection

      Nota:

      • -occurs when the infectious agent enter the body and start reproduction -may or may not lead disease
      1. Pathogen

         Nota:

         • -a type of infectious agent can cause disease
      2. Host

         Nota:

         • -an organism infected by another organism
      3. Virulence

         Nota:

         • the relative ability of an agent can cause rapid and severe disease in a host
   3. Prevalence

      Nota:

      • -number of cases at a given time -expressed as a percent at a given time =product of incidence x duration of disease(long duration:hepatitis B)
   4. Contamination

      Nota:

      • The presence of an infectious agent on different kinds of material/substances(e.g. water, a body surface, clothes)
   5. Disease

      Nota:

      • -a pathological condition -characterized by signs and symptoms
   6. Immunogenicity

      Nota:

      • The ability of an organism to produce immune response after an infection: -providing protection against a similar or the same organism(e.g. infectious agents)
   7. Vector of infection

      Nota:

      • an insect or any living carriers:transport an infectious agent from an infected individual/its wastes to other susceptible individuals/food/surroundings.
   8. Reservoir

      Nota:

      • any person,animal, arthropod, plant, soil or substance or combination of these:allow an infectious agent to live and multiplies. -an infectious agent are transmittable to other susceptible(natural habitat)
   9. Imapparent infection

      Nota:

      • -no detectable clinical symptoms -can be documented by :    1.isolation of a pathogen,     2. detection of it component(DNA)    3. produce a specific immune response in                 person(asymptomatic)
   10. Incidence

       Nota:

       • 1.number of new cases in a given time period 2.expressed as percent infected per year/number per person time of observation
   11. Special terms
       1. Nosocomial

          Nota:

          • 1. an infection originating in a patient while in a hospital 2. not related to the patient's primary condition-e.g. infection of surgical wound, hepatitis B, urinary tract infection
          1. Opportunistic infections

             Nota:

             • infection by organisms -take opportunity provided by a defect in host defense -organism infect the host and cause disease. 
       2. Eradication

          Nota:

          • -aims to termination of all transmission of infection(extermination of the infectious agent) -absolute process(an all or non phenomenon)
          1. Elimination

             Nota:

             • It is used to describe eradication of a disease(e.g. measles/polio) from a large geographic  region.
       3. Reproductive rate

          Nota:

          • It describes the potential for an infectious disease to spread. Influential factors: 1.probability of transmission 2.frequency of population contact 3.virulence of the organism 4.population immune proportion 5.duration of infection
2. Causes
   1. Genetic
   2. Biological
   3. Physical
   4. Environment
   5. Chemical
3. Early history

   Nota:

   • 1.Smallpox-trigger epidemic in ancient Greece and Egypt 2.Plague-coinfect with measles and smallpox  3.Syphilis- spreadly rapidly through europe in 1490s and cause high mortality
4. Koch's Postulates(a particular agent can cause a specific disease)

   Nota:

   • 1. specific agent must be associated with every case of the disease. 2. the agent can be isolated from a diseased host and grown in culture 3. the culture-grown agent is introduced into a healthy species must cause the same disease 4.the same agent must be again isolated from the infected host
5. Caused by infectious disease agents

   Nota:

   • 1.microbes/microorganisms -bacteria -viruses -protozoa -fungi -Helminths(animals)
   1. MOA for induceing disease

      Nota:

      • 1.production of poisons(enzymes or toxins) 2.direct invasion and destruction 3.trigger immune responsed
6. Phases
   1. Incubation period

      Nota:

      • Time between infection and apparent of symptoms
      1. Prodromal period

         Nota:

         • mild,non specific symptoms that signal onset of some disease
         1. Clinical phase

            Nota:

            • a person experiences typical signs and symptoms
            1. Decline phase

               Nota:

               • subsidence of symptoms
               1. Recovery phase

                  Nota:

                  • symptoms have disappeared -tissue heal -body remains strength
7. Classifications
   1. By duration

      Nota:

      • 1. Acute 2.Chronic 3.Latent -characterized by periods of no symptoms between outbreaks of illness
   2. By location

      Nota:

      • 1. Local- confined to a specific area of body 2. Systemic- infects most of the body with pathogens distributed widely in tissues
   3. By Timing

      Nota:

      • 1. Primary:initial infection in a healthy person 2. Secondary:infection that occurs in a person weakened by a primary infection
   4. Clinical

      Nota:

      • 1. Diarrheal diseases 2. Respiratory diseases 3. Central nervous system infection 4. Cardiovascular infection 5.Sepsis
   5. Microbiological

      Nota:

      • 1. Bacterial 2. Viral 3. Fungal 4. Parasitic 5. Prion
   6. Transmission

      Nota:

      • 1. Contact(direct/indirect) 2. Food/water borne 3. Airborne 4. Vecter borne 5. Perinatal:occurs during pregnancy
   7. Reservoir

      Nota:

      • 1. Human:HIV, HBV 2. Animals: Rabies 3. Soil 4. Water:Pseudomonas aeruginosa
8. The severe level
   1. Endemic

      Nota:

      • The constant of a disease or infectious agent within a given geographic area
   2. Pandemic

      Nota:

      • an worldwide epidemic affect high proportion of global population
   3. Epidemic

      Nota:

      • The occurrence of a disease/illnesses excess of what may be expected on the basis of past experience for a given population
9. Transmission

   Nota:

   • 1.air 2.contaminated food/water 3. body fluids 4.Direct contact 5.animal vectors
   1. Reducing spreading

      Nota:

      • 1.Vaccines 2.Antimicrobial drugs 3.Good personal hygiene 4.Protection against vectors 5.Quarantine