Understanding Human Diseases: Types, Defenses, and Treatments

Posted on Nov 28, 2024 in Biology

Noninfectious Diseases

These diseases affect the body’s organ systems. They can be categorized as:

  • Inherited or Genetic Diseases: Passed down from parents, often chronic (e.g., diabetes, hemophilia).
  • Mental Diseases: Cause abnormal personality disorders (e.g., neurosis, schizophrenia). Treatment may involve psychotropic drugs, therapy, and support.
  • Specific Organ/System Diseases: Affect particular organs or body systems, such as the digestive, circulatory, nervous, musculoskeletal, endocrine, or sensory systems.
  • Autoimmune Diseases: Result from the immune system attacking the body, causing damage across multiple organ systems (e.g., multiple sclerosis). Immunomodulatory drugs may be used.
  • Diseases Caused by Accidents: Include those from traffic, domestic, or industrial incidents.

Infectious Diseases

Prevalence refers to the number of people with a disease at a given time, while incidence refers to new cases appearing in a population. Infection occurs when a pathogen transmits from a source to a host. Key pathogen characteristics include:

  • Contagiousness: The organism’s capacity to spread.
  • Infectivity: Ability to settle and multiply.
  • Pathogenicity: Ability to produce disease.
  • Virulence: Degree of pathogenicity.

Reservoirs of Infection

Before infecting humans, pathogens reside in locations called reservoirs, where they reproduce and transmit. Reservoirs can be animals (sick or healthy), soil, or water.

Routes of Pathogen Transmission

  • Fecal-oral route: Ingestion of contaminated food or water (e.g., diarrhea).
  • Respiratory tract: Inhalation of infected droplets (e.g., pneumonia).
  • Contact: Person-to-person (e.g., leprosy), animal contact or bites/stings (e.g., malaria), or injuries (e.g., tetanus).

Phases of Infectious Diseases

  • Incubation period: Time from organism entry to first symptoms.
  • Prodromal period: Nonspecific general signs appear.
  • Clinical period: Onset of defining symptoms and diagnosis. This is followed by a convalescent period of recovery.

Prevention of Infectious Diseases

Prevention involves targeting the reservoir/source or the susceptible host. This includes community disease monitoring, isolation, health education, vaccination, and passive immunization with sera.

Koch’s Postulates

These postulates determine if an organism is a disease agent:

  1. The organism is always present in sick individuals.
  2. The organism can be isolated from the sick host.
  3. The disease is reproduced when the culture is inoculated into a healthy host.
  4. The organism can be re-isolated from the infected host and grown in the lab.

Body Defenses Against Infection

The body’s immune system defends against foreign substances (antigens). Immunity is the resistance against pathogen-caused infections. The immune response is triggered by antigens. There are two types of immunity:

  • Innate Immunity: Present from birth, passed from mother to child. Includes external defenses, phagocytes (white blood cells), and blood proteins. The inflammatory reaction is an example.
  • Adaptive Immunity: Acquired throughout life after pathogen contact, provided by lymphocytes and antibodies. Generates immunological memory.

Outer Defenses

  • Skin: Impermeable to microorganisms.
  • Mucous membranes: Secrete mucus to prevent bacterial attachment.
  • Saliva, tears, and urine: Destroy or impede germ development.
  • Biological barriers: Prevent pathogenic organism growth.

Inflammatory Response

Inflammation is the first defense when germs breach external barriers. Symptoms include swelling, heat, redness, and pain. Stages involve:

  1. Production of inflammatory mediators: fluid and substance release by damaged cells.
  2. Reactions in the affected area: increased blood flow and capillary permeability. Phagocytes create pus.

Fighting Infectious Diseases

Healing methods include serum therapy, vaccines, and drugs (chemotherapy).

Serums

Artificial preparations containing specific antibodies from blood. Provide immediate passive immunity, which disappears as antibodies are eliminated.

Vaccines

Preparations containing a non-damaging form of the pathogen. They trigger an immune response similar to natural infection without virulence or risk.

Drugs

Chemotherapy controls infectious diseases with drugs, most importantly antibiotics. Antibiotics are substances produced by microorganisms that inhibit bacterial growth. They are used prophylactically (preventively) or therapeutically (curatively) against bacterial infections.

Rational Use of Medicines

A drug is a substance used to prevent, diagnose, treat, cure disease, or modify physiological functions. It’s an active ingredient developed for medical use.

Drug Use and WHO

WHO defines reasonable drug use as patients receiving appropriate medications for their clinical needs, in measured doses, with usage information. This involves:

  • Choosing the right medication for the patient’s clinical situation, excluding self-medication.
  • Providing clear and accurate information on how to take the drug, dosage, and duration. Treatment should not be abandoned without medical consultation.
  • Prescribing the cheapest medicine among available options.
Responsible Use of Antibiotics

Antibiotics are used preventively or curatively against infection. They can be specific or broad-spectrum. Penicillin was the first discovered; others include erythromycin and tetracycline. Antibiotics are ineffective against viruses and fungi. Overuse can lead to bacterial resistance. Responsible consumption involves avoiding self-medication and adhering strictly to prescribed dosages.