Question

Describe two ways in which a pre-existing virus can become an emerging virus.

Short answer

A mutation is the main reason that causes the formation of new strains of viruses. The immune system cannot fight even the original strain of the virus that infects the animal.

The second way of creating new emerging strains from pre-existing strains is the spread the viral disease in a small and isolated population. This virus can infect a new host and become emergent.

Step-by-step solution

Virus

Viruses are smaller and structurally simpler than eukaryotes and prokaryotes. They lack cellular machinery, or the so-called particles containing a DNA segment inside a protein coat. They cause a very broad range of diseases like AIDS. They cannot do any metabolic activity outside the host cell, so they are considered non-living.

Step 2: Emerging Virus

Emerging viruses are so-called because they suddenly appear in a population. For example, HIV is an emergent virus that infected a few people in San Francisco and is prevalent everywhere now. Other examples are viruses causing encephalitis, West Nile virus, etc.

Step 3: Formation of emerging virus from pre-existing virus

Two ways by which emerging virus was created from the pre-existing virus are:

1. When a mutation occurs in the pre-existing virus, a new virus strain is produced that is more harmful to the living organisms. It can cause disease even if an organism is immune to its pre-existing form. Mostly it is created by the mutation in RNA virus because viral RNA polymerase lacks proof-reading ability. For example, seasonal flu epidemics are due to infection with emerging new strains of the influenza virus.
2. A second way of the emergence of new strains is the dissemination of the virus to a new population from a small and isolated population. One example is the AIDS virus that became emergent after infection from a small population to a large area of the world.