Human Diseases

Infectious Diseases

Disease	Causative agent	Transmission / key fact
Tuberculosis (TB)	Bacterium: Mycobacterium tuberculosis	Mainly airborne particles from infectious pulmonary TB. BCG vaccine is used in many national programmes.
Cholera	Bacterium: Vibrio cholerae	Contaminated water or food; can cause severe watery diarrhoea and dehydration.
Typhoid	Bacterium: Salmonella Typhi	Contaminated food/water; sanitation and safe water are important prevention measures.
Tetanus	Bacterium: Clostridium tetani	Spores enter wounds; not ordinarily spread person-to-person. Prevented by vaccination and wound care.
Leprosy	Bacterium: Mycobacterium leprae	Prolonged close contact is associated with transmission; affects skin and peripheral nerves. Curable with multidrug therapy.
Plague	Bacterium: Yersinia pestis	Often transmitted by infected fleas; pneumonic plague can spread via respiratory droplets.
Diphtheria	Bacterium: Corynebacterium diphtheriae	Respiratory droplets/contact; vaccine-preventable.
Pertussis (whooping cough)	Bacterium: Bordetella pertussis	Respiratory droplets; vaccine-preventable.
Malaria	Plasmodium parasites	Transmitted by infected female Anopheles mosquitoes.
Dengue	Dengue virus	Mainly Aedes mosquitoes; prevention centres on avoiding bites and eliminating breeding sites.
Chikungunya	Chikungunya virus	Aedes mosquitoes; fever and often severe joint pain.
Lymphatic filariasis	Parasitic filarial worms	Mosquito-borne; may cause lymphoedema and elephantiasis.
Kala-azar	Leishmania parasites	Transmitted by infected female sandflies; may cause prolonged fever and enlarged spleen.
Amoebiasis	Entamoeba histolytica	Fecal–oral route via contaminated food or water.
Rabies	Rabies virus	Usually transmitted through saliva from an infected mammal, often via a bite; urgent post-exposure care is essential.
Polio	Poliovirus	Mainly fecal–oral transmission; vaccination prevents disease.
Measles	Measles virus	Airborne; highly contagious and vaccine-preventable.
Hepatitis A	Hepatitis A virus	Usually fecal–oral, often via contaminated food/water.
Hepatitis B	Hepatitis B virus	Blood and body fluids, sexual contact and perinatal transmission; vaccine available.
HIV infection / AIDS	Human immunodeficiency virus	Blood, sexual fluids and breast milk; not spread by casual contact. ART controls HIV but does not routinely cure it.
Influenza	Influenza viruses	Respiratory transmission; seasonal vaccines are updated periodically.
COVID-19	SARS-CoV-2	Mainly spreads through infectious respiratory particles.
Ringworm	Fungi (dermatophytes)	Skin contact, infected animals or contaminated objects; despite its name, not caused by a worm.
Ascariasis	Ascaris lumbricoides worm	Ingestion of eggs from contaminated soil, food or hands.

Diseases and Nutritional Deficiencies

Nutrient	Deficiency / disease	Typical association
Vitamin A	Night blindness; xerophthalmia	Impaired vision in dim light; severe deficiency damages the eye.
Vitamin B1 (thiamine)	Beriberi	Nerve and cardiovascular problems.
Vitamin B3 (niacin)	Pellagra	Classically dermatitis, diarrhoea and dementia; untreated severe disease can be fatal.
Vitamin B9 (folate)	Megaloblastic anaemia	Important in DNA synthesis; deficiency during pregnancy raises neural-tube-defect risk.
Vitamin B12	Megaloblastic anaemia; neurological problems	May cause nerve damage as well as anaemia.
Vitamin C	Scurvy	Bleeding gums, poor wound healing and connective-tissue problems.
Vitamin D	Rickets in children; osteomalacia in adults	Poor bone mineralisation.
Vitamin E	Rare deficiency can cause neurological or muscle problems	Risk is higher in some fat-absorption disorders.
Vitamin K	Impaired blood clotting	May increase bleeding.
Iron	Iron-deficiency anaemia	Low haemoglobin; fatigue and weakness may occur.
Iodine	Goitre; impaired thyroid hormone production	Severe deficiency in pregnancy/early life can impair brain development.
Calcium	Poor bone mineralisation; hypocalcaemia-related symptoms	Bone health and muscle/nerve function.
Protein-energy malnutrition	Kwashiorkor, marasmus	Severe undernutrition; clinical presentations may overlap.

PYQs

1. Carrier of Malaria disease is— [Miscellaneous 2023]

(A) Aedes Mosquito

(B) Culex Mosquito

(D) Mansonia Mosquito

Answer: (C) Anopheles Mosquito

2. Zika virus disease is transmitted through—[Miscellaneous 2018]

(A) Mosquito

(B) Dog

(D) Bird

Answer: (A) Mosquito

3. Ascariasis spreads through—[Miscellaneous 2012]

(A) Polluted air

(B) Polluted water

(D) Direct physical touch

Answer: (C) Contaminated food

4. Which of the following is a water-borne disease? [Miscellaneous 2018]

(A) Tuberculosis

(B) Typhoid

(D) Tetanus

Answer: (B) Typhoid

5. Which of the following is a disease transmitted through blood?[Miscellaneous 2019]

(A) Cholera

(B) Tuberculosis

(D) Pneumonia

Answer: (C) AIDS