Understanding Communicable Diseases

Communicable Diseases Overview

• Communicable diseases involve a chain of infection: an agent (bacteria, viruses, fungi, protozoa) infecting a reservoir, entering through a portal of entry (nose, skin, sex), transmitting via various modes, and exiting through a portal (airborne droplets, blood, contact).

Body's Defense Mechanisms

• The first line of defense includes the skin, tears, mucus, saliva, cilia, stomach acid, urine flow, and normal flora.
• The second line of defense involves leukocytes (white blood cells) and cytokines.

Immunity Types

• Natural immunity has two types: passive (maternal) and active (acquired from exposure, e.g., measles).
• Artificial immunity is also classified into passive (short-term) and active (tetanus toxoid, DPT, BCG).

Epidemiology

• Epidemiology studies disease distribution and occurrence.
  • Sporadic cases are isolated incidents.
  • Endemic diseases are consistently present in a local area (e.g., malaria).
  • Epidemics spread rapidly across regions (e.g., dengue).
  • Pandemics affect nations worldwide (e.g., COVID-19).

Inflammation

• Cardinal signs of inflammation are:
  • Calor (heat).
  • Dolor (pain).
  • Rubor (redness).
  • Function laesa (loss of function).
  • Tumor (swelling).

Prevention Strategies

• Prevention includes:
  • Following airborne (N95 mask), droplet (surgical mask, coughing etiquette), and contact (gown, gloves, mask, goggles, face shield) precautions.
  • Practicing proper hand hygiene.
  • Maintaining safe sexual practices (limiting partners, regular screening).
  • Ensuring transfusion safety.
  • Keeping vaccinations up to date to maintain immunity.

Ecologic Model

• The ecologic model illustrates the interaction between the agent, host, and environment in communicable diseases.
• Susceptible hosts lacking immunity are vulnerable.
• The environment can favor either the host or the agent.

Integumentary Diseases

Measles

• Rubeola virus (paramyxovirus) causes measles, which is highly contagious.
• Transmission occurs through airborne secretions.
• Koplik spots (oral mucosa) and maculopapular rash (trunk to arms) are primary signs.
• Treatment includes airborne precautions, calamine lotion, Vitamin A supplementation, and symptomatic management (avoiding ibuprofen).
• Prevention: Live vaccine is contraindicated during pregnancy, breastfeeding, and in immunocompromised individuals.

Chickenpox

• Varicella-zoster virus causes chickenpox, which is self-limiting.
• It transmits via airborne routes.
• Presents with centripetal rashes and life-time immunity.
• Treatment includes antivirals, antipyretics, antihistamines, and calamine lotion.

Shingles

• Herpes zoster virus causes shingles, marked by ray-like, painful rashes, mostly affecting adults.
• Transmission occurs through droplets.
• Treatment includes acyclovir, pain medications, antipyretics, and antihistamines.

Hansen's Disease (Leprosy)

• Mycobacterium leprae is the causative agent, leading to a chronic, debilitating disease.
• Transmission occurs via prolonged skin-to-skin contact.
• Early signs are "an-an" (loss of sensation) on the skin and peripheral nerve enlargement.
• Focus is on preventing injuries.

Scabies

• Sarcoptes scabiei (small worms) cause scabies, transmitted through skin contact.
• Common in overpopulated communities.
• Presents with weeping itch and itchy papulovesicular lesions.

German Measles

• Transmits via droplets/ maternal route.
• Shows blueish Forsheimer's spots.

Respiratory Diseases

Pneumonia

• Pneumonia can be caused by S. aureus or S. pneumoniae and is communicable via droplets.
• Symptoms include rusty sputum, coryza, and orthopnea.

Tuberculosis

• Mycobacterium tuberculosis causes TB, spread through airborne transmission.
• Diagnosis involves sputum AFB tests, chest X-rays, and PPD tests.
• Treatment includes rifampicin, isoniazid, pyrazinamide, ethambutol and streptomycin.

COVID-19

• SARS-CoV-2 causes severe acute respiratory syndrome.
• Spread by airbourne droplets.
• Symptoms include fever with history of travel, lung tissue inflammation, and impaired blood clotting.

Ebola

• Ebola is caused by the Ebola virus and causes severe respiratory infections.
• History of travel to south america and parts of africa is a primary indicator.

Gastrointestinal Diseases

Typhoid Fever

• Salmonella typhosa causes typhoid fever, transmitted through infected urine/feces and contaminated food/water.
• Enlargement of lymphoid tissues and spleen occurs (spleenomegaly).

Cholera

• Vibrio cholerae causes cholera, leading to a profuse dehydration and vomiting.
• Transmitted through water and feces

Dysentery

• Bacillary dysentery causes Dysentery.
• The stools has blood in them and can be prevented through yellow tagging.

Amobiasis

• Protozoal infection on the Colon - liver and lungs.
• Causes watery diarreha

Blood Borne Diseases

Malaria

• Anopheles mosquitos transmits Malaria.
• Involves stages within the liver and red blood cells.
• Causing spleen and hepatomegaly

Dengue

• Mosquito transmission (aedes aegypti).
• Can lead to dengue shock syndrome

Filiarisis

• Parasitic disease spread trhough mosquito bites and causes issues such as fever, lymphangitis or nocturnal asthama.

Menincococcemia

• caused by neisseria meningitidis spread trhough droplets
• causes rapid decline and potential amputations

Hepatitis

• Viral infections that leads to liver cirrosis.
• Types include: A (enteric), B (serum), and C (parenteral).
• Prevention includes immunization and safe practices.

Poliomyelitis

• acute paralytic infection spread via feces.
• can be prevented through vaccine