Answer: Infection occurs when the host is exposed to pathogens. virus uses the cell's metabolism, and replicates itself while destroying the cell or changing the cell's genetic makeup.

Explanation:

A virus is a miniscule pocket of protein that contains genetic material.

Viruses pose a considerable challenge to the body’s immune system because they hide inside cells.
This makes it difficult for antibodies to reach them. Some special immune system cells, called T-lymphocytes, can recognise and kill cells containing viruses, since the surface of infected cells is changed when the virus begins to multiply.
Many viruses, when released from infected cells, will be effectively knocked out by antibodies that have been produced in response to infection or previous immunisation.
Antibiotics are useless against viral infections. So antiviral drugs work differently to antibiotics, by interfering with the viral enzymes instead.

Hence virus are the pathogen that use the cell's metabolism. And replicate itself while destroying the cell or changing the cell's genetic makeup. viruses are so simple that they use their host cells to perform their activities for them

Learn more about virues :

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