Communicable Diseases Quiz

Communicable Diseases

• Communicable diseases are illnesses caused by pathogenic organisms (bacteria, viruses, fungi, or protozoa).
• They can spread from person to person or from organism to organism.

Modes of Transmission

• Direct contact: Direct physical contact, touching surfaces with pathogens
• Indirect contact: Touching surfaces containing pathogens (e.g., coughing/sneezing)
• Droplet: Via coughing and sneezing
• Airborne: Transmitted through air particles
• Vehicle: Food-borne (from food source), water-borne (from water source)
• Vector-borne: Through insects or animals

Basic Terminology

• Epidemic: Unexpected increase in disease cases in a specific geographical area (temporary).
• Endemic: Disease consistently present in a particular region.
• Pandemic: Disease rapidly spreading globally.

Vaccines

• Vaccines are biological preparations for triggering an immune response to fight against diseases.
• Aim: Stimulating antibody production for natural disease fighting.
• Mechanism of action varies depending on vaccine type.

Types of Vaccines

• Whole pathogen vaccine
• Viral vectored vaccine
• Subunit vaccine
• Nucleic acid vaccine
• Toxoid vaccine

Acquired Immunodeficiency Syndrome (AIDS)

• Late stage HIV infection with badly damaged immune system.
• Caused by HIV virus (commonly HIV-1).
• Diagnosis involves:
  • CD4 cell count below 200 cells/mm³
  • Opportunistic infections.
• HIV statistics (end of 2020, WHO):
  • 37.6 million people living with HIV infection
  • 670,000 deaths
• HIV causative agent: retrovirus.
  • Two types:
    • Type 1 is more common globally including sub-Saharan Africa
    • Type 2 mostly in West Central Africa, parts of Europe, and India.

HIV structure

• Spherical, ~100nm in diameter
• Contains:
  • Envelope proteins (gp120, gp41)
  • RNA
  • Lipid membrane
  • Reverse transcriptase
  • Matrix protein (p17)
  • Capsule protein (p24)
  • Nucleocapsid protein (p24)

HIV Transmission

• Common: Unprotected sex with infected partner, sharing needles with infected person
• Minimally common: Transmission from infected mother to fetus, infection from blood products

HIV Life Cycle

• HIV binds to a CD4 receptor on the CD4 cell.
• HIV fuses with the host cell, releasing genetic material.
• Reverse transcriptase converts viral genetic material to DNA.
• DNA integrates into the host cell's DNA.
• Virus stays inactive as provirus.
• The active virus uses host enzymes to produce more genetic material and proteins.
• New virus particles are assembled.
• The new virus pushes out of the host cell and uses part of the host cell membrane for its outer covering, allowing infection of a new cell
• HIV is now complete and ready to infect new cells

HIV Clinical Stages (WHO)

• Stage 1: Asymptomatic
• Stage 2: Mild symptoms; low CD4 levels
• Stage 3: Advanced symptoms; immune system deteriorates
• Stage 4: Severe symptoms; AIDS/ rapid CD4 count decline

HIV Opportunistic Infections

• Kaposi's sarcoma

HIV Diagnostic Methods

• Microplate ELISA: Colored wells indicate HIV reactivity.
• HIV Rapid Test: Qualitative membrane strip; colored line indicates positive result.
• Laboratory tests:
  • ELISA/Rapid assay (screening, high sensitivity/specificity)
  • Western Blot (confirmatory, lower sensitivity than ELISA).
    • Absolute CD4 lymphocyte count
    • HIV viral Load

HIV Treatment and Prevention

• Treatment: Antiretroviral therapy (ART) to suppress/slow virus replication
• Prevention:
  • Safe sex practices
  • Prevent mother-to-child transmission
  • Avoid sharing needles/equipment
  • Safe blood transfusions

Dengue Fever

• Mosquito-borne viral infection (tropical/subtropical climates)
• Caused by Dengue Virus (DENV, Flaviviridae).
• Four serotypes (1-4).
• Incubation period: 4-10 days
• Transmitted by mosquitos (Aedes aegypti/albopictus)
• Also a vector for other viral diseases.

Types of Dengue Fever

• Classical dengue fever: High fever, pain, rash, mild bleeding.
• Dengue hemorrhagic fever (DHF): High fever, severe pain, bleeding, and organ impairment.
• Dengue shock syndrome (DSS): High fever, severe pain, severe bleeding and organ failure.

Dengue Fever Symptoms

• Symptoms varies by type and severity

Dengue Fever Diagnosis

• Laboratory tests:
  • Culture
  • Serology (antibody detection, NS1)
  • Molecular diagnosis (NAATs/RT-PCR)

Dengue Fever Treatment and Prevention

• Treatment: Supportive care, fluid replacement.
• Prevention: Mosquito control, vector avoidance.

Tuberculosis

• Infectious bacterial disease (M. tuberculosis complex; M. bovis, M. africanum, M. microti, M. caprae, M. pinnipedii, M. canettii, and M. mungi).
• Transmission: Airborne droplets (Inhalation), digestive tract. Droplet size matters for transmission
• Symptoms: Fever, chills, cough (sputum, hemoptysis), night sweats, fatigue, weight loss;
• Finger clubbing: May occur.

Tuberculosis Diagnosis

• Tuberculin skin test (Mantoux test)
• Nucleic analysis (PCR, hybridization)
• Culture media: Lowenstein-Jensen, Middlebrook 7H10, Ogawa

Tuberculosis Treatment

• Anti-TB drugs: First/second line drugs
  • Isoniazid
  • Ethambutol
  • Rifampicin
  • Pyrazinamide
  • Streptomycin (previously, but other less effective drugs)
• MDR-TB: Drug-resistant Tuberculosis
• Regimen time varies by country and severity/ resistance

Tuberculosis Prevention

• BCG Vaccine: Live attenuated Mycobacterium bovis

Malaria

• Infection of red blood cells by Plasmodium parasites.
• Transmission: Infected female Anopheles mosquitoes (bites).
• Species:
  • P. falciparum
  • P. vivax
  • P. ovale
  • P. malariae
  • P. knowlesi
• Incubation period: 10-14 days (Average)

Malaria Life Cycle

• Mosquito injects sporozoites.
• Sporozoites infect liver cells.
• Merozoites are released to red blood cells, causing symptoms
• Infected red blood cells rupture, releasing more merozoites.
• Some merozoites develop into gametocytes.
• Gametocytes are ingested by a mosquito, completing the cycle.

Malaria Symptoms

• Symptoms vary significantly ranging from fever and chills to severe complications
• Mild/uncomplicated: fever, cold/shivering, headaches, vomit, seizures, sweating, tiredness
• Severe/complicated: coma, metabolic acidosis, severe anemia, hypoglycemia, acute kidney failure, or pulmonary edema

Malaria Diagnosis

• Blood film: Detection of parasites.
• Rapid diagnostic test (RDT): Quick detection of malaria.
• Serology tests: Antibody detection.
• Polymerase chain reaction (PCR): Detection of parasite DNA.
• Full blood count (FBC): Check blood composition to ensure no irregularities
• Blood Urea Serum Electrolytes (BUSE): Monitoring electrolyte imbalance.
• Inflammation blood marker: C-reactive protein
• Liver function tests: Liver profile
• Glucose

Malaria Treatment

• Artemisinin combination therapies (ACTs): (first line treatment)
  • Artesunate + mefloquine
  • Artemether + lumefantrine
• Antipysretics
• Anti-emetics
• Anti-convulsants
• Fluids
• Blood transfusion
• Anti-biotics (for serious infections).

Malaria Prevention

• Insecticide-treated bed nets
• Indoor residual spraying (insecticides)
• Preventive therapies (pregnant women, children, and infants).

Candidiasis

• Fungal infection caused by Candida (yeast).

• Common: Candida albicans

• Other types: Candida glabrata, tropicalis etc

• Normal flora: Skin, mouth, throat, gut, and vagina.

• Overgrowth/immunocompromised: Infections trigger

Candidiasis Symptoms

• Mouth: White patches, redness, cotton-like feel, loss of taste, pain with eating
• Vaginal: Whitish frothy discharge, itchiness
• Skin: Redness, inflammation

Candidiasis Diagnosis

• Microscopy
• Culture (Sabouraud dextrose agar)
• Skin or blood analysis

Candidiasis Treatment

• Drugs:
  • Fluconazole
  • Itraconazole
  • Clotrimazole
  • Miconazole
  • Nystatin