Influenza virus has –
**Core Concept**
Influenza virus is a type of RNA virus that belongs to the Orthomyxoviridae family. It is a major cause of respiratory illness worldwide, with seasonal epidemics affecting millions of people each year.
**Why the Correct Answer is Right**
Influenza virus has a unique characteristic that allows it to evade the host's immune system and cause repeated infections. The virus's surface protein, hemagglutinin (HA), undergoes antigenic drift, resulting in minor changes to the virus's surface proteins. This enables the virus to infect the same host multiple times, even if they have been previously infected or vaccinated.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the influenza virus is not a DNA virus; it is an RNA virus.
**Option B:** This option is incorrect because the influenza virus does not have a lipid envelope; it is a helical virus with a single-stranded RNA genome.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the influenza virus has two main surface proteins: hemagglutinin (HA) and neuraminidase (NA). These proteins play a crucial role in the virus's ability to infect and spread within the host.
**Correct Answer:** D.