Influenza viruses are divided into which major groups?

Influenza viruses are divided into which major groups?

• A. A, B, and C
• B. X, Y, Z
• C. Primary, secondary
• D. DNA, RNA

Answer: (A)

Influenza viruses are categorized into three major groups: A, B, and C. This classification is based on differences in their core proteins, notably the nucleoprotein and matrix proteins, which define distinct types with different host ranges and antigenic profiles. Type A is found in many animal species and humans and is the source of most pandemics; it has a wide array of surface subtypes defined by hemagglutinin and neuraminidase proteins, contributing to its great variability. Type B mostly infects humans (and some seals) and causes seasonal epidemics but lacks the same breadth of subtypes. Type C tends to cause milder respiratory illness and does not contribute to large outbreaks. The other naming schemes—X, Y, Z; primary, secondary; or labeling by DNA versus RNA—do not reflect how influenza is actually grouped, since influenza viruses are RNA viruses and are not classified by those criteria.

Influenza viruses are categorized into three major groups: A, B, and C. This classification is based on differences in their core proteins, notably the nucleoprotein and matrix proteins, which define distinct types with different host ranges and antigenic profiles. Type A is found in many animal species and humans and is the source of most pandemics; it has a wide array of surface subtypes defined by hemagglutinin and neuraminidase proteins, contributing to its great variability. Type B mostly infects humans (and some seals) and causes seasonal epidemics but lacks the same breadth of subtypes. Type C tends to cause milder respiratory illness and does not contribute to large outbreaks. The other naming schemes—X, Y, Z; primary, secondary; or labeling by DNA versus RNA—do not reflect how influenza is actually grouped, since influenza viruses are RNA viruses and are not classified by those criteria.