Correct Option
The correct option is (a).
Explanation
Communicable diseases are classified based on the specific pathogen responsible for the infection. These pathogens include bacteria, viruses, protozoa, fungi, and helminths. Identifying the causative agent is fundamental to understanding the pathology and treatment of the disease.
Statement-wise Analysis
- Statement 1 is Correct: Typhoid fever is caused by the bacterium Salmonella typhi. Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis. Both are bacterial infections.
- Statement 2 is Incorrect: Polio (Poliomyelitis) is caused by the Poliovirus. Chickenpox is caused by the Varicella-zoster virus. Therefore, both are viral diseases, not bacterial.
- Statement 3 is Incorrect: Dysentery is an infection of the intestines resulting in bloody diarrhea. It is primarily caused by bacteria (Bacillary dysentery, caused by Shigella) or protozoa (Amoebic dysentery, caused by Entamoeba histolytica). It is not typically classified as a viral disease in standard medical taxonomy.
Key Takeaway: Typhoid and Tuberculosis are bacterial diseases; Polio and Chickenpox are viral diseases; Dysentery is caused by bacteria or protozoa.