Master10
Human Body & Medicine Module

Human Diseases, Pathogens & Epidemiology

Pathological conditions in humans are classified into communicable infectious diseases caused by pathogens (viruses, bacteria, protozoa, fungi, helminths) and non-communicable lifestyle disorders. Bacterial diseases include tuberculosis (caused by Mycobacterium tuberculosis), typhoid (Salmonella typhi, confirmed via the Widal test), and cholera (Vibrio cholerae). Viral infections include influenza, rabies, hepatitis, dengue, and HIV/AIDS, which attacks CD4+ T-lymphocytes. Vector-borne protozoan illnesses include malaria, caused by Plasmodium parasites transmitted by female Anopheles mosquitoes. Non-communicable diseases—including cardiovascular conditions, hypertension, type 2 diabetes mellitus, and cancer—constitute the leading causes of global mortality, monitored through public health surveillance frameworks.

Key Concepts & Examination Highlights

  • Malaria is caused by the protozoan parasite Plasmodium and is transmitted to humans through the bite of an infected female Anopheles mosquito.
  • The Widal test is the standard serological diagnostic test used to detect enteric fever caused by Salmonella typhi (Typhoid).
  • Tuberculosis is caused by the acid-fast bacterium Mycobacterium tuberculosis, primarily affecting pulmonary lung tissue.
  • Dengue, Chikungunya, and Zika viruses are transmitted to humans primarily through the bite of infected Aedes aegypti and Aedes albopictus mosquitoes.
  • Cholera is an acute diarrheal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae, treated primarily with Oral Rehydration Salts (ORS).
  • Human Immunodeficiency Virus (HIV), a retrovirus utilizing reverse transcriptase, selectively infects and depletes CD4+ T-helper lymphocytes, progressing to AIDS.
  • Kala-azar (visceral leishmaniasis) is caused by the protozoan parasite Leishmania donovani and is transmitted by the bite of infected Phlebotomine sandflies.
  • Rabies is a fatal viral encephalitis caused by a lyssavirus, transmitted through the saliva of infected animals (most commonly dogs) and characterized by hydrophobia.
  • Leprosy (Hansen's disease) is a chronic granulomatous infection of peripheral nerves and skin caused by Mycobacterium leprae, treated with Multi-Drug Therapy (MDT).
  • Hepatitis B is a double-stranded DNA viral infection transmitted via infected blood and bodily fluids that damages hepatocytes and can cause chronic cirrhosis or hepatocellular carcinoma.
  • Type 1 diabetes is an autoimmune disorder resulting in the destruction of insulin-producing pancreatic beta cells, whereas Type 2 diabetes involves progressive peripheral insulin resistance.
  • Chikungunya is a vector-borne viral disease caused by an alphavirus transmitted by Aedes aegypti and Aedes albopictus mosquitoes, characterized by acute fever and debilitating polyarthralgia.
  • Lymphatic filariasis (elephantiasis) is caused by filarial nematodes such as Wuchereria bancrofti and Brugia malayi, transmitted by Culex mosquitoes and causing chronic lymphedema of limbs.
  • Japanese Encephalitis is a flavivirus infection transmitted by infected Culex tritaeniorhynchus mosquitoes breeding in flooded paddy fields, causing acute inflammation of brain parenchyma.
  • Trachoma, caused by the bacterium Chlamydia trachomatis, is a leading infectious cause of preventable blindness worldwide, transmitted through contact with discharge from eyes and nose of infected persons.
  • Tetanus (lockjaw) is caused by the neurotoxin tetanospasmin produced by the anaerobic spore-forming bacterium Clostridium tetani, which enters through contaminated puncture wounds and induces violent muscle spasms.
  • Diphtheria is an upper respiratory tract infection caused by Corynebacterium diphtheriae, producing an exotoxin that forms a thick gray pseudomembrane across the tonsils and pharynx.
  • Pertussis (whooping cough) is a highly contagious respiratory infection caused by the bacterium Bordetella pertussis, characterized by paroxysmal coughing episodes followed by a high-pitched inspiratory whoop.
  • Plague is a zoonotic disease caused by the bacterium Yersinia pestis, maintained in rodent populations and transmitted to humans via bites from infected rat fleas (Xenopsylla cheopis).
  • Zika virus is an arbovirus transmitted by Aedes mosquitoes that causes mild fever and maculopapular rash, but maternal infection during pregnancy can induce congenital microcephaly and neurological abnormalities.
  • Mpox (formerly monkeypox) is a zoonotic viral disease caused by the monkeypox virus (an orthopoxvirus), presenting with fever, painful lymphadenopathy, and progressive vesicular and pustular skin lesions.
  • Sickle cell anemia is an autosomal recessive genetic disorder caused by a single point mutation in the β\beta-globin gene (GAG→GTGGAG \rightarrow GTG, substituting glutamic acid with valine), producing abnormal hemoglobin S (HbS).
  • Hemophilia is an X-linked recessive bleeding disorder where Hemophilia A is caused by deficiency of clotting Factor VIII and Hemophilia B (Christmas disease) is caused by deficiency of clotting Factor IX.
  • Down syndrome (Trisomy 21) is a chromosomal aneuploidy caused by non-disjunction of chromosome 21 during gametogenesis, characterized by distinct facial features, hypotonia, and developmental delays.
  • Parkinson's disease is a progressive neurodegenerative movement disorder characterized by resting tremor, bradykinesia, and rigidity, resulting from the selective degeneration of dopaminergic neurons in the substantia nigra.
  • Atherosclerosis is a chronic inflammatory vascular disease characterized by the buildup of fibrofatty plaques in arterial walls, narrowing vascular lumens and causing coronary artery disease.
  • Hypertension in adults is clinically defined by standard guidelines as a sustained systolic blood pressure ≥130 extmmHg\ge 130 \ ext{ mmHg} or diastolic blood pressure ≥80 extmmHg\ge 80 \ ext{ mmHg}.
  • Cirrhosis is the end-stage histological outcome of chronic liver diseases, characterized by diffuse hepatic fibrosis, regenerative nodules, and portal hypertension.
  • Chronic Obstructive Pulmonary Disease (COPD) is a progressive inflammatory lung disease encompassing chronic bronchitis and emphysema, primarily triggered by chronic tobacco smoke inhalation.
  • Asthma is a chronic inflammatory disorder of the airways characterized by reversible bronchoconstriction, airway hyperresponsiveness, and excessive mucus secretion.
  • Alzheimer's disease is a neurodegenerative disorder characterized histopathologically by extracellular beta-amyloid senile plaques and intracellular hyperphosphorylated tau neurofibrillary tangles.
  • Amyotrophic Lateral Sclerosis (ALS), or Lou Gehrig's disease, is a progressive neurodegenerative disease selectively destroying upper and lower motor neurons in the spinal cord and motor cortex.
  • Multiple Sclerosis (MS) is a chronic autoimmune demyelinating disease of the central nervous system where T-cells attack oligodendrocytes and myelin sheaths.
  • Systemic Lupus Erythematosus (SLE) is a multi-system autoimmune disease characterized by the production of antinuclear antibodies (ANA) and anti-double-stranded DNA (anti-dsDNA) antibodies.
  • Rheumatoid arthritis is a systemic autoimmune disorder characterized by symmetric chronic inflammatory synovitis of diarthrodial joints, mediated by rheumatoid factor and anti-CCP antibodies.
  • Celiac disease is an autoimmune enteropathy triggered by the ingestion of dietary gluten (proteins in wheat, rye, and barley) in genetically susceptible individuals expressing HLA-DQ2 or HLA-DQ8.
  • Inflammatory Bowel Disease (IBD) encompasses Crohn's disease (transmural skip lesions anywhere along the GI tract) and Ulcerative Colitis (continuous mucosal inflammation restricted to the colon).
  • Gout is a painful metabolic arthropathy caused by the deposition of monosodium urate monohydrate crystals in synovial fluid and periarticular tissues due to chronic hyperuricemia.
  • Osteoarthritis is a degenerative joint disease characterized by progressive breakdown of articular cartilage, subchondral bone remodeling, and osteophyte formation at joint margins.
  • Osteoporosis is a systemic skeletal disease characterized by low bone mineral density and microarchitectural deterioration of bone tissue, assessed via Dual-energy X-ray Absorptiometry (DEXA T-score ≤−2.5\le -2.5).
  • Ebola virus disease is a severe filovirus hemorrhagic fever transmitted through direct contact with infected blood and bodily fluids, characterized by high case fatality rates up to 90%.
  • Marburg virus disease is a genetically related filoviral hemorrhagic fever maintained in Egyptian rousette fruit bat reservoirs and transmitted through direct contact with infected fluids.
  • Lassa fever is an acute viral hemorrhagic fever caused by an arenavirus transmitted to humans through contact with food or household items contaminated with urine or feces of Mastomys rats.
  • Crimean-Congo Hemorrhagic Fever (CCHF) is a tick-borne bunyavirus disease transmitted through the bite of infected Hyalomma ticks or direct contact with blood of infected livestock.
  • Nipah virus is a zoonotic paramyxovirus maintained in Pteropus fruit bats (flying foxes) that causes severe acute encephalitis and respiratory distress with human-to-human transmission potential.
  • Kyasanur Forest Disease (KFD), or monkey fever, is a tick-borne flavivirus hemorrhagic fever endemic to the Western Ghats region of India, transmitted by Haemaphysalis ticks.
  • Brucellosis is a zoonotic bacterial infection caused by Brucella species transmitted via unpasteurized dairy products or contact with infected cattle, sheep, and goats, causing undulant fever.
  • Leptospirosis (Weil's disease) is a spirochetal zoonotic disease caused by Leptospira interrogans shed in rodent urine, entering humans through broken skin in floodwaters.
  • Schistosomiasis (bilharzia) is a parasitic water-borne disease caused by trematode flatworms of the genus Schistosoma, where cercariae penetrate human skin in freshwater harboring infected snails.
  • Dracunculiasis (Guinea worm disease) is an eradicable parasitic nematode infection caused by Dracunculus medinensis, transmitted by drinking water contaminated with parasite-infected copepod water fleas.
Curriculum & Reference Sources: World Health Organization (WHO Disease Surveillance), Indian Council of Medical Research (ICMR), CDC

Sample Solved Questions & Concept Explanations

8 Verified Concept Questions
Q1.EASY

Which blood group is known as the 'Universal Donor' in the ABO and Rh blood group system?

Q2.EASY

Which blood group is known as the 'Universal Recipient'?

Q3.EASY

Which infectious disease is caused by the parasite Plasmodium, transmitted through female Anopheles mosquito bites?

Q4.EASY

Which disease is characterized by chronic high levels of glucose in the blood due to insulin deficiency or resistance?

Q5.MEDIUM

What type of immunity is acquired when antibodies are directly transferred from mother to fetus across the placenta (IgG) or via breastmilk (IgA)?

Q6.MEDIUM

What is the medical term for high blood pressure?

Q7.HARD

Which antibody isotype exists predominantly as a secretory dimer in mucosal secretions (saliva, tears, colostrum, GI mucus)?

Q8.EASY

Which infectious mosquito-borne disease is caused by the protozoan parasite Plasmodium and transmitted to humans by female Anopheles mosquitoes?