Which of the following types of influenza are the most common and cause seasonal epidemics?


i. Influenza A.
ii. Influenza B.
iii. Influenza C.

• A. I & II.
• B. I & III.
• C. II & III.
• D. I, II, & III.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the classification of influenza viruses. Influenza viruses are categorized into types A, B, and C based on their core proteins and genetic makeup.
2. Step 2: Recognize the epidemiological significance of each type. Influenza A viruses are known for causing widespread seasonal epidemics and pandemics due to their ability to undergo antigenic shift and drift.
3. Step 3: Consider Influenza B viruses, which also contribute to seasonal epidemics but generally cause less severe outbreaks compared to Influenza A. They mainly infect humans and have less genetic variability.
4. Step 4: Note that Influenza C viruses typically cause mild respiratory illness and are not associated with seasonal epidemics or widespread outbreaks.
5. Step 5: Conclude that the types most commonly responsible for seasonal epidemics are Influenza A and Influenza B, while Influenza C is not a major cause of such epidemics.