Diseases & Pathogens

A pathogen is any organism that causes disease. In competitive exams, the primary focus is distinguishing between diseases caused by Viruses, Bacteria, and Fungi, as well as the history of immunology.

• Viruses: Microscopic parasites that reproduce only inside a host's living cells. Not affected by antibiotics.
• Bacteria: Single-celled organisms that can live in diverse environments. Can be treated with antibiotics.
• Protozoa: Single-celled eukaryotes, often parasitic (e.g., Malaria parasite).
• Fungi: Organisms like mold or yeast that can cause skin and systemic infections.

• Antibiotics (like Penicillin) are completely ineffective against viruses because viruses lack cell walls and metabolic machinery.
• Edward Jenner developed the first-ever vaccine in 1796 for Smallpox.
• Alexander Fleming discovered the first antibiotic, Penicillin, from a mold (Penicillium notatum) in 1928.
• Louis Pasteur developed the process of Pasteurization and the first vaccine for Rabies.
• Malaria is transmitted to humans by the bite of an infected female Anopheles mosquito.

• Q: Who is the "Father of Immunology"?
• A: Edward Jenner.
• Q: Which pathogen causes the disease Malaria?
• A: Protozoa (Plasmodium).
• Q: Is the Common Cold caused by bacteria or a virus?
• A: Virus (Rhinovirus).
• Q: What was the first antibiotic ever discovered?
• A: Penicillin.

"Hydrophobia is a symptom associated with which of the following diseases?"

A) Typhoid

B) Rabies

C) Cholera

D) Malaria

(Correct: B - Rabies)