Human Diseases — 50+ Diseases with Causative Agents, Symptoms, Prevention, and Vaccines

Aspirants preparing for the Lower Division Clerk, Last Grade Servant, and Kerala Administrative Service exams can utilize this set of study notes on human diseases to reinforce their understanding of biology, particularly in areas such as bacterial diseases like tuberculosis, viral diseases including influenza, and protozoan diseases like malaria. The difficulty level of these notes is reference-oriented, making them suitable for candidates who have already covered the basics of human health and disease. Use this set after revising the chapter on human diseases to test recall of key terms like causative agents and vaccines, such as the role of Plasmodium vivax in malaria. Reviewing these notes will help solidify your grasp of diseases caused by helminths and fungi, so review explanations after submission to lock weak areas and focus on symptom identification and prevention methods for optimal results. Human diseases is one of the most heavily tested topics in Kerala PSC exams. Expect 3-5 questions in every Graduate Level paper. These notes cover 50+ diseases systematically by type.

1. Bacterial Diseases

Disease	Causative Agent	Transmission	Key Symptoms	Prevention/Vaccine
Tuberculosis (TB)	Mycobacterium tuberculosis	Airborne (droplets)	Chronic cough, blood in sputum, fever, weight loss	BCG vaccine; DOTS treatment
Cholera	Vibrio cholerae	Contaminated water/food	Severe watery diarrhoea (“rice-water stools”), dehydration	ORS, clean water, oral cholera vaccine
Typhoid	Salmonella typhi	Contaminated water/food	Step-ladder fever, rose spots on abdomen, headache	Widal test (diagnosis); typhoid vaccine
Plague	Yersinia pestis	Flea bite (rat flea)	Bubonic: swollen lymph nodes (buboes); Pneumonic: lung infection	Rat control, antibiotics
Diphtheria	Corynebacterium diphtheriae	Airborne (droplets)	Grey membrane in throat, bull-neck swelling	DPT/DTP vaccine
Tetanus (Lockjaw)	Clostridium tetani	Wound infection (anaerobic)	Muscle stiffness, jaw lock, painful spasms	TT (Tetanus Toxoid) vaccine; DPT
Whooping Cough (Pertussis)	Bordetella pertussis	Airborne (droplets)	Severe coughing fits with “whooping” sound	DPT vaccine
Leprosy (Hansen’s Disease)	Mycobacterium leprae	Prolonged close contact	Skin patches with loss of sensation, nerve damage	MDT (Multi-Drug Therapy); India eliminated leprosy (prevalence rate basis) in 2005
Pneumonia	Streptococcus pneumoniae (and others)	Airborne	Fever, cough, chest pain, difficulty breathing	Pneumococcal vaccine
Syphilis	Treponema pallidum	Sexual contact	Painless sores (chancre), rashes, late-stage organ damage	Antibiotics (penicillin); safe practices
Gonorrhoea	Neisseria gonorrhoeae	Sexual contact	Burning urination, discharge	Antibiotics; safe practices
Anthrax	Bacillus anthracis	Contact with infected animals/spores	Cutaneous: black sore; Pulmonary: severe pneumonia	Anthrax vaccine (for high-risk workers)
Botulism	Clostridium botulinum	Contaminated food (toxin)	Paralysis, blurred vision, difficulty swallowing	Proper food preservation
Meningitis (bacterial)	Neisseria meningitidis	Airborne (droplets)	Stiff neck, high fever, headache, sensitivity to light	Meningococcal vaccine
Leptospirosis	Leptospira species	Contact with infected animal urine, floodwater	Fever, muscle pain, jaundice (Weil’s disease)	Doxycycline prophylaxis; avoid floodwater

PSC Favourite: “Which disease is diagnosed by Widal test?” — Typhoid.

2. Viral Diseases

Disease	Causative Agent	Transmission	Key Symptoms	Prevention/Vaccine
COVID-19	SARS-CoV-2	Airborne/droplets	Fever, cough, breathlessness, loss of taste/smell	Covishield, Covaxin, and others
AIDS	HIV (Human Immunodeficiency Virus)	Blood, sexual contact, mother-to-child	Progressive immune system failure; opportunistic infections	No vaccine; ART (Antiretroviral Therapy)
Dengue	Dengue virus (DENV 1-4)	Aedes aegypti mosquito bite	High fever, severe headache, joint pain (“breakbone fever”), rash	Mosquito control; no widely used vaccine in India
Chikungunya	Chikungunya virus	Aedes aegypti/albopictus	Fever, severe joint pain and swelling	Mosquito control
Rabies	Rabies virus (Lyssavirus)	Bite of infected animal (dog, bat)	Hydrophobia (fear of water), paralysis, fatal if untreated	Post-exposure vaccine (PEP); pre-exposure vaccine for high-risk
Measles	Measles virus (Morbillivirus)	Airborne	Fever, cough, Koplik spots (mouth), rash	MMR vaccine (Measles, Mumps, Rubella)
Mumps	Mumps virus	Airborne/droplets	Swelling of parotid glands, fever	MMR vaccine
Rubella (German Measles)	Rubella virus	Airborne	Mild fever, rash; dangerous in pregnancy (congenital defects)	MMR vaccine
Poliomyelitis (Polio)	Poliovirus	Faecal-oral	Paralysis (especially legs), muscle weakness	OPV (Oral Polio Vaccine — Sabin); IPV (Injectable — Salk)
Hepatitis A	HAV	Faecal-oral (contaminated water)	Jaundice, fatigue, nausea	Hepatitis A vaccine; clean water
Hepatitis B	HBV	Blood, sexual contact	Jaundice, liver cirrhosis, liver cancer	Hepatitis B vaccine (part of Universal Immunisation Programme)
Hepatitis C	HCV	Blood (transfusion, needles)	Chronic liver disease, cirrhosis	No vaccine; antiviral treatment available
Influenza (Flu)	Influenza virus (A, B, C)	Airborne/droplets	Fever, body ache, cough, runny nose	Annual flu vaccine
Smallpox	Variola virus	Airborne/contact	Fever, fluid-filled pustules on skin	Eradicated globally in 1980 (WHO); Edward Jenner — first vaccine (1796)
Ebola	Ebola virus	Contact with body fluids	Haemorrhagic fever, internal bleeding, high mortality	rVSV-ZEBOV vaccine
Zika	Zika virus	Aedes mosquito; sexual contact	Mild fever; microcephaly in newborns (if mother infected)	Mosquito control; no vaccine
Yellow Fever	Yellow Fever virus	Aedes aegypti	Fever, jaundice, bleeding	Yellow Fever vaccine (17D)
Japanese Encephalitis	JE virus	Culex mosquito	Fever, headache, brain inflammation, seizures	JE vaccine (SA 14-14-2)
Nipah	Nipah virus (NiV)	Fruit bats (Pteropus); direct contact	Fever, headache, encephalitis; high mortality	No vaccine; Kerala outbreaks in 2018 and 2023

PSC Favourite: “Which virus causes AIDS?” — HIV. “Who discovered HIV?” — Luc Montagnier and Robert Gallo (1983).

Kerala Special: Nipah virus outbreaks in Kozhikode (2018) and Kozhikode (2023) — fruit bats identified as reservoir.

3. Protozoan Diseases

Disease	Causative Agent	Transmission	Key Symptoms	Prevention/Treatment
Malaria	Plasmodium (P. vivax, P. falciparum, P. malariae, P. ovale)	Female Anopheles mosquito	Recurring fever with chills and sweating (every 48 or 72 hrs)	Mosquito nets, antimalarials (chloroquine, ACT); no widely used vaccine (RTS,S in trials)
Amoebic Dysentery (Amoebiasis)	Entamoeba histolytica	Contaminated water/food	Bloody diarrhoea, abdominal pain	Clean water; metronidazole
Sleeping Sickness	Trypanosoma brucei	Tsetse fly	Fever, sleep disturbances, coma	Vector control (Africa; not in India)
Kala-azar (Visceral Leishmaniasis)	Leishmania donovani	Sandfly bite	Irregular fever, enlarged spleen and liver, weight loss, darkening of skin	Insecticide spraying; amphotericin B
Giardiasis	Giardia lamblia	Contaminated water	Diarrhoea, bloating, nausea	Clean water; metronidazole

PSC Favourite: “Malaria is caused by which organism?” — Plasmodium. “Vector of malaria?” — Female Anopheles mosquito.

4. Fungal Diseases

Disease	Causative Agent	Affected Area	Key Features
Ringworm (Dermatophytosis)	Trichophyton, Microsporum	Skin, nails, scalp	Circular, itchy, red patches; NOT caused by a worm
Athlete’s Foot	Trichophyton	Feet (between toes)	Itchy, peeling skin
Candidiasis (Thrush)	Candida albicans	Mouth, throat, genital area	White patches in mouth; common in immunocompromised
Aspergillosis	Aspergillus	Lungs	Cough, fever; serious in immunocompromised patients
Mucormycosis (Black Fungus)	Mucor/Rhizopus	Sinuses, brain, lungs	Black lesions, facial swelling; surged during COVID-19 second wave in India (2021)

5. Helminthic (Worm) Diseases

Disease	Causative Agent	Transmission	Key Features
Ascariasis	Ascaris lumbricoides (roundworm)	Faecal-oral	Abdominal pain, malnutrition in children
Filariasis (Elephantiasis)	Wuchereria bancrofti	Culex mosquito	Massive swelling of limbs and genitals
Tapeworm infection	Taenia solium (pork), T. saginata (beef)	Undercooked meat	Abdominal pain, segments in stool
Hookworm	Ancylostoma duodenale	Skin penetration (walking barefoot)	Anaemia, fatigue
Pinworm	Enterobius vermicularis	Faecal-oral	Perianal itching, common in children

6. Deficiency Diseases

Disease	Deficiency	Key Symptoms
Scurvy	Vitamin C	Bleeding gums, loose teeth, poor wound healing
Rickets	Vitamin D	Soft, bent bones in children
Osteomalacia	Vitamin D	Soft bones in adults
Night Blindness	Vitamin A	Inability to see in dim light
Xerophthalmia	Vitamin A (severe)	Dry eyes, corneal damage, blindness
Beriberi	Vitamin B1 (Thiamine)	Wet: heart failure, oedema; Dry: nerve damage
Pellagra	Vitamin B3 (Niacin)	3 Ds: Dermatitis, Diarrhoea, Dementia
Anaemia	Iron	Fatigue, pallor, breathlessness
Goitre	Iodine	Swelling of thyroid gland
Kwashiorkor	Protein	Swollen belly, oedema, stunted growth (children)
Marasmus	Protein and calories	Extreme wasting, thin limbs (children)

PSC Favourite: “Pellagra is caused by deficiency of?” — Vitamin B3 (Niacin). “3 Ds of Pellagra?” — Dermatitis, Diarrhoea, Dementia.

7. Vectors and the Diseases They Transmit

Vector	Diseases Transmitted
Female Anopheles mosquito	Malaria
Aedes aegypti mosquito	Dengue, Chikungunya, Zika, Yellow Fever
Culex mosquito	Filariasis, Japanese Encephalitis, West Nile Fever
Rat flea (Xenopsylla cheopis)	Plague
Sandfly (Phlebotomus)	Kala-azar (Leishmaniasis)
Tsetse fly	Sleeping Sickness (African Trypanosomiasis)
Dog/bat bite	Rabies
Housefly	Typhoid, Cholera, Dysentery (mechanical vector)
Body louse	Typhus
Tick	Lyme disease, Crimean-Congo Haemorrhagic Fever

8. Important Vaccines — Discovery and Type

Vaccine	Disease	Discoverer/Developer	Type
BCG	Tuberculosis	Albert Calmette, Camille Guerin	Live attenuated
OPV (Sabin)	Polio	Albert Sabin	Live attenuated (oral)
IPV (Salk)	Polio	Jonas Salk	Inactivated (injectable)
DPT/DTP	Diphtheria, Pertussis, Tetanus	Combined vaccine	Toxoid + inactivated
MMR	Measles, Mumps, Rubella	Combined vaccine	Live attenuated
Covaxin	COVID-19	Bharat Biotech + ICMR	Inactivated whole virus
Covishield	COVID-19	AstraZeneca/Oxford (SII in India)	Viral vector (adenovirus)
Hepatitis B	Hepatitis B	Maurice Hilleman	Recombinant
Smallpox	Smallpox	Edward Jenner (1796)	Live (cowpox virus) — first vaccine ever

9. National Health Programmes

Programme	Target Disease/Goal
Universal Immunisation Programme (UIP)	12 vaccine-preventable diseases in children
Pulse Polio	Polio eradication (India declared polio-free in 2014)
RNTCP/NTEP	TB elimination by 2025 (now NTEP — National TB Elimination Programme)
NVBDCP	Vector-borne diseases (malaria, dengue, chikungunya, kala-azar, filariasis)
NACP	AIDS/HIV control
NLEP	Leprosy elimination
NMHP	Mental health
Ayushman Bharat	Universal health coverage

10. Major Epidemics in India — Timeline

Year	Epidemic	Key Facts
1896-1900	Bubonic Plague	Bombay; massive mortality; led to Plague Commission
1918-1919	Spanish Flu (Influenza)	12-17 million deaths in India — deadliest epidemic in Indian history
1994	Plague (Surat)	Pneumonic plague outbreak; mass exodus from Surat
2006	Chikungunya	Major outbreak in Kerala, Karnataka, Andhra Pradesh
2009	H1N1 (Swine Flu)	Pandemic; Pune was the Indian epicentre
2014	Ebola	Not in India but caused global alert
2018	Nipah (Kerala)	Kozhikode; 17 deaths; fruit bat reservoir identified
2020-2023	COVID-19	Massive impact; India was second-most-affected country
2021	Mucormycosis (Black Fungus)	Surged during COVID second wave; especially in diabetes patients
2023	Nipah (Kerala)	Second outbreak in Kozhikode; contained quickly

11. Previous Year PSC-Style Questions

Question	Answer
BCG vaccine is for which disease?	Tuberculosis
Vector of dengue?	Aedes aegypti mosquito
Deficiency of Vitamin D causes?	Rickets (children), Osteomalacia (adults)
First vaccine was discovered by?	Edward Jenner (Smallpox, 1796)
India was declared polio-free in?	2014
Widal test is used to diagnose?	Typhoid
Nipah virus outbreaks in Kerala occurred in?	2018 and 2023 (both in Kozhikode)
Causative agent of cholera?	Vibrio cholerae
Pellagra is caused by deficiency of?	Vitamin B3 (Niacin)
Which disease is also called “breakbone fever”?	Dengue
DOTS is the treatment strategy for?	Tuberculosis
Smallpox was eradicated globally in?	1980