Human Diseases — Study Notes for Railway Group D

Overview

Human diseases form a core topic in the General Science section of Railway Group D exams, typically yielding 2–4 direct questions. The topic divides cleanly into **communicable diseases** (infectious, spread from person to person or through vectors) and **non-communicable diseases** (lifestyle-related, genetic, or degenerative conditions). Exam questions test your ability to identify disease causes (pathogen type), modes of transmission, symptoms, and preventive measures.

Mastery requires memorizing specific disease-pathogen pairs, understanding vector vs. non-vector transmission, and recognizing basic prevention strategies like vaccination, sanitation, and lifestyle modification. Questions often present a symptom or cause and ask you to name the disease, or vice versa. You must also distinguish between bacterial, viral, protozoan, and fungal infections, as well as recognize deficiency diseases and lifestyle disorders.

This topic connects directly to practical public health awareness—expect questions framed around government health campaigns (Pulse Polio, Swachh Bharat) and everyday hygiene practices relevant to railway operations and public safety.

Key Concepts

• **Communicable diseases** are caused by pathogens (bacteria, viruses, fungi, protozoa, helminths) and spread via direct contact, air, water, food, vectors (mosquitoes, flies), or contaminated objects.
• **Non-communicable diseases (NCDs)** do not spread from person to person; they arise from genetic factors, lifestyle choices (diet, exercise, smoking), environmental exposures, or aging processes.
• **Pathogens** invade the body, multiply, and disrupt normal function. The immune system fights back using white blood cells, antibodies, and memory cells for future protection.
• **Vectors** are living organisms (usually insects) that carry pathogens from one host to another without suffering from the disease themselves (e.g., female *Anopheles* mosquito transmits malaria).
• **Prevention methods** include vaccination (active immunity), maintaining hygiene, safe drinking water, vector control (insecticides, bed nets), balanced nutrition, regular exercise, and avoiding tobacco/alcohol.
• **Deficiency diseases** result from lack of essential nutrients (vitamins, minerals, proteins) and are a subset of non-communicable diseases—malnutrition weakens immunity and increases susceptibility to infections.
• **Antibiotics** treat bacterial infections but are ineffective against viruses; misuse leads to antibiotic resistance, a growing public health concern.
• **Lifestyle diseases** like diabetes, hypertension, and heart disease result from poor diet, sedentary habits, stress, and substance abuse; they are preventable through behavior modification.

Key Facts

1. **Tuberculosis (TB)**: Caused by *Mycobacterium tuberculosis* (bacteria); spreads through air (coughing, sneezing); affects lungs primarily; preventable by BCG vaccine; symptoms include persistent cough, weight loss, night sweats. 2. **Malaria**: Caused by *Plasmodium* parasite (protozoa); transmitted by female *Anopheles* mosquito; symptoms include recurring fever, chills, sweating; prevented by mosquito nets, eliminating stagnant water. 3. **Dengue**: Caused by dengue virus; transmitted by *Aedes aegypti* mosquito (day-biting); symptoms include high fever, severe joint pain, rash, low platelet count; no specific vaccine widely available in India yet. 4. **Typhoid**: Caused by *Salmonella typhi* (bacteria); spreads through contaminated food/water; symptoms include prolonged fever, abdominal pain, weakness; prevented by safe water, sanitation, and typhoid vaccine. 5. **Cholera**: Caused by *Vibrio cholerae* (bacteria); spreads via contaminated water; symptoms include severe watery diarrhea, dehydration; prevented by ORS (oral rehydration solution), clean water, hygiene. 6. **AIDS (Acquired Immunodeficiency Syndrome)**: Caused by HIV (Human Immunodeficiency Virus); spreads through infected blood, sexual contact, mother to child; destroys immune cells; no cure but antiretroviral therapy (ART) controls progression; prevented by safe practices, screening blood donations. 7. **Diabetes Mellitus**: Non-communicable; high blood sugar due to insufficient insulin or insulin resistance; Type 1 (genetic/autoimmune), Type 2 (lifestyle-related); complications include kidney damage, blindness, heart disease; managed by diet, exercise, medication. 8. **Hypertension (High Blood Pressure)**: Non-communicable; persistently elevated blood pressure damages heart and blood vessels; causes include excess salt, obesity, stress, lack of exercise; often called "silent killer" as symptoms appear late. 9. **Polio (Poliomyelitis)**: Caused by poliovirus; spreads through contaminated food/water; can cause permanent paralysis; India declared polio-free in 2014 due to Pulse Polio immunization campaign. 10. **Cancer**: Non-communicable; uncontrolled cell division forming tumors; causes include tobacco, radiation, genetic mutations, certain viruses (HPV); types include lung, breast, oral, blood (leukemia); prevented by avoiding carcinogens, early screening. 11. **Goiter**: Deficiency disease caused by lack of iodine; thyroid gland enlarges; prevented by iodized salt consumption. 12. **Scurvy**: Deficiency disease caused by lack of Vitamin C; symptoms include bleeding gums, weakness; prevented by citrus fruits and fresh vegetables.