Bacteria, Viruses, and Protists

Virus Basics

Why is it difficult to treat viral infections with medications?

Antibiotics are ineffective against viral infections because viruses lack the structures (for example, a cell wall) with which antibiotics interfere. In general, it is difficult to treat viral infections with medications without affecting the host cell as viruses use the host cell’s machinery during replication. Thus, even though some antiviral medications exist, it is truly the body’s immune system that fights off viral infections.

But still, several antiviral drugs have been developed that are effective against certain viruses—the following chart lists some of them:


Viral pathogen

Antiviral drug


Human immunodeficiency

Azidathymidine (AZT), virus didanosine, dideoxycytosine

Chronic hepatitis

Hepatitis B or C

interferon alfa-2B

Genital herpes, shingles, chicken pox


Acyclovir, idoxuridine, trifluridine, vidarabine

Influenza A




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