Biology

Sub-topics in Common Diseases in Humans

Biology·Revision Notes

Infectious Diseases — Revision Notes

NEET UG
Updated 22 Mar 2026

⚡ 30-Second Revision

  • Pathogens: — Viruses, Bacteria, Fungi, Protozoa, Helminths.
  • Transmission: — Direct (contact, droplets), Indirect (airborne, vehicle, vector, fomite).
  • Key Diseases & Agents:

- Typhoid: Salmonella typhi (bacterium) - Pneumonia: Streptococcus pneumoniae (bacterium) - Common Cold: Rhinoviruses (virus) - Malaria: Plasmodium (protozoan), vector: female Anopheles mosquito - Amoebiasis: Entamoeba histolytica (protozoan) - Ascariasis: Ascaris lumbricoides (helminth) - Filariasis: Wuchereria bancrofti (helminth), vector: Culex mosquito - Ringworm: Microsporum, Trichophyton (fungi) - AIDS: HIV (retrovirus), targets THT_H cells

  • Malaria Cycle: — Human (liver, RBCs) ↔\leftrightarrow Mosquito (gut, salivary glands).
  • AIDS Transmission: — Sexual, blood, mother-to-child. NOT casual contact.
  • Prevention: — Vaccination, hygiene, sanitation, vector control.

2-Minute Revision

Infectious diseases are caused by pathogens like viruses, bacteria, fungi, protozoa, and helminths. They spread through various modes: direct contact (e.g., common cold via droplets), indirect means like contaminated food/water (e.

g., typhoid, amoebiasis), or vectors (e.g., malaria and filariasis via mosquitoes). Key diseases to remember include Typhoid (bacterial, fecal-oral), Pneumonia (bacterial/viral, droplet), Common Cold (viral, droplet), Malaria (protozoan, mosquito-borne, cyclic fever), Amoebiasis (protozoan, fecal-oral, dysentery), Ascariasis (helminth, fecal-oral, intestinal blockage), Filariasis (helminth, mosquito-borne, elephantiasis), Ringworm (fungal, direct contact, skin lesions), and AIDS (viral, sexual/blood/mother-to-child, targets THT_H cells leading to immunodeficiency).

Prevention relies on sanitation, hygiene, vaccination, and vector control. Treatment varies by pathogen type (antibiotics for bacteria, antivirals for viruses, etc.).

5-Minute Revision

Infectious diseases are illnesses resulting from pathogenic invasion. Pathogens include viruses (e.g., Rhinoviruses for Common Cold, HIV for AIDS), bacteria (e.g., Salmonella typhi for Typhoid, Streptococcus pneumoniae for Pneumonia), protozoa (e.g., Plasmodium for Malaria, Entamoeba histolytica for Amoebiasis), fungi (e.g., Microsporum for Ringworm), and helminths (e.g., Ascaris lumbricoides for Ascariasis, Wuchereria bancrofti for Filariasis).

Transmission can be direct (e.g., common cold via respiratory droplets) or indirect. Indirect methods include vehicle-borne (e.g., typhoid via contaminated food/water), vector-borne (e.g., malaria by female Anopheles mosquito, filariasis by Culex mosquito), and fomite-borne. AIDS, caused by HIV, is transmitted through sexual contact, contaminated blood, and from mother to child, but crucially NOT through casual contact.

Symptoms are diverse: Typhoid presents with high fever and intestinal issues; Pneumonia with fluid-filled alveoli and respiratory distress; Malaria with recurrent chills and fever due to RBC rupture; Amoebiasis with dysentery; Ascariasis with intestinal blockage and anemia; Filariasis with chronic inflammation leading to elephantiasis; Ringworm with itchy, scaly skin lesions; and AIDS with severe immunodeficiency leading to opportunistic infections.

Prevention strategies are vital: vaccination (e.g., for typhoid), maintaining personal and public hygiene, ensuring safe drinking water and food, and controlling disease vectors. Treatment involves specific drugs like antibiotics for bacterial infections, antimalarials for malaria, and antiretroviral therapy for HIV, emphasizing that antibiotics are ineffective against viral infections.

Prelims Revision Notes

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  1. Infectious Diseases: — Caused by pathogens (viruses, bacteria, fungi, protozoa, helminths). Transmissible.
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  2. Pathogens:

* Viruses: Rhinoviruses (Common Cold), HIV (AIDS). * Bacteria: Salmonella typhi (Typhoid), Streptococcus pneumoniae, Haemophilus influenzae (Pneumonia). * Protozoa: Plasmodium spp. (Malaria), Entamoeba histolytica (Amoebiasis). * Fungi: Microsporum, Trichophyton, Epidermophyton (Ringworm). * Helminths: Ascaris lumbricoides (Ascariasis), Wuchereria bancrofti, W. malayi (Filariasis).

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  1. Modes of Transmission:

* Fecal-oral: Typhoid, Amoebiasis, Ascariasis (contaminated food/water). * Droplet/Airborne: Common Cold, Pneumonia. * Vector-borne: Malaria (female Anopheles mosquito), Filariasis (Culex mosquito). * Sexual/Blood/Mother-to-child: AIDS. * Direct Contact: Ringworm.

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  1. Key Symptoms & Affected Organs:

* Typhoid: Sustained high fever, constipation, intestinal perforation (intestine). * Pneumonia: Fever, chills, cough, fluid-filled alveoli (lungs). * Common Cold: Nasal congestion, sore throat (nasal passage, respiratory tract).

* Malaria: Recurrent chills and high fever (RBCs rupture), headache (RBCs, liver). * Amoebiasis: Constipation, abdominal pain, blood/mucus in stools (large intestine). * Ascariasis: Internal bleeding, muscular pain, anemia, intestinal blockage (intestine).

* Filariasis: Chronic inflammation, elephantiasis (lymphatic vessels, lower limbs, genital organs). * Ringworm: Dry, scaly, itchy lesions (skin, nails, scalp). * AIDS: Immunodeficiency, opportunistic infections (helper T-lymphocytes).

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  1. Life Cycles:

* Malaria: Human (asexual in liver then RBCs) ↔\leftrightarrow Mosquito (sexual in gut, sporozoites in salivary glands). * Filariasis: Human (lymphatic vessels) ↔\leftrightarrow Mosquito (larval development).

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  1. Diagnosis: — Widal test (Typhoid), ELISA/Western Blot (AIDS), blood smear (Malaria, Filariasis), stool test (Amoebiasis, Ascariasis).
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  2. Prevention: — Vaccination, sanitation, hygiene, vector control, safe practices (e.g., safe sex).
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  3. Treatment: — Antibiotics (bacterial), Antimalarials (Malaria), Antifungals (Ringworm), Anthelmintics (Ascariasis, Filariasis), ART (AIDS). Antibiotics are ineffective against viruses.

Vyyuha Quick Recall

To remember the common infectious diseases and their types: Tiny Pathogens Cause Many Ailments, And Fungi Really Annoy Skin.

  • Typhoid (Bacterial)
  • Pneumonia (Bacterial/Viral)
  • Common Cold (Viral)
  • Malaria (Protozoan)
  • Amoebiasis (Protozoan)
  • Ascariasis (Helminth)
  • Filariasis (Helminth)
  • Ringworm (Fungal)
  • AIDS (Viral - specifically Sexually transmitted, targets immune system)