Key Abbreviations in Immunology — NEET Biology

Correct answer: C — S1, S2, S3 and S4 only

This question tests the understanding of Typhoid fever, its causative agent, transmission, diagnosis, and the concept of carriers, as discussed in NCERT. Let's evaluate each statement: - **S1: Typhoid fever is a bacterial disease caused by Salmonella typhi.** This statement is correct. NCERT states, 'Salmonella typhi is a pathogenic bacterium which causes typhoid fever in human beings.' (Page 130) - **S2: The pathogen primarily enters the small intestine through contaminated food and water.** This statement is correct. NCERT mentions, 'These pathogens generally enter the small intestine through food and water contaminated with them'. (Page 130) - **S3: Individuals like 'Typhoid Mary' are known as chronic carriers and can spread the disease for extended periods without severe symptoms.** This statement is correct. NCERT describes Mary Mallon as 'a typhoid carrier who continued to spread typhoid for several years'. (Page 131) - **S4: The Widal test is a diagnostic tool used to confirm the presence of typhoid fever.** This statement is correct. NCERT mentions, 'Typhoid fever could be confirmed by Widal test'. (Page 131) - **S5: Intestinal perforation and death are typical outcomes for all infected individuals.** This statement is incorrect. NCERT states, 'Intestinal perforation and death may occur in severe cases', implying it's not a typical outcome for all cases. (Page 130) Therefore, statements S1, S2, S3, and S4 are correct. Option C correctly identifies S1, S2, S3, and S4 as accurate statements about typhoid fever.