A virus, considered a microorganism, consists of an ultramicroscopic fragment of either DNA or RNA with a protein sheath wrapped around it. Unlike bacteria, viruses do not grow, play no valuable role in earthly life and show no sign of activity other than replication. Viruses lack the chemical machinery to generate energy, so they rely on a host's chemical components to replicate themselves. This renders the virus harmless outside of the body but dangerous once it enters.
Types of Viruses
Some of the more well-known viruses today include the herpes virus, herpes simplex virus, cytomegalovirus, retrovirus, HIV, influenza A strain, influenza A and B strains, picornavirus, and hepatitis B and C. Antiviral medicine grew out of the bacterial medicine frenzy that followed Louis Pasteur's development of penicillin.
Antiviral Drug Targets
The formulation of antiviral drugs developed according to the individual virus' weak points. For instance, the herpes virus drugs target polymerase, an enzyme that helps in the formation of polymer, needed to build a larger compound from smaller molecules. By rendering polymerase non-functional, the virus cannot replicate. The antiretroviral drugs that fight HIV aim at the virus' reverse transcriptase, a DNA polymerase directed at RNA. Again, the aim becomes interruption of the replication process, according to Fundamental of Microbiology, 5th ed.
Classes of Antiviral Drugs
Classified by the mechanisms they use to work, the antiviral drugs break down into seven types. According to Microbiology Bytes, the drugs that treat the herpes viruses, cytomegalovirus and the retroviruses make up the "nucleoside analogue" class. These include: vidarabine, acyclovir, gancyclovir, valganciclovir, zidovudine, didanosine, zalcitabine, stavudine, lamivudine, nevirapine and delavirdine. Within this group sub categories exist. Another HIV drug class, the peptide analogues, includes the protease inhibitors saquinavir, ritonavir, indinavir and nelfinavir. Ribavirin inoculates against measles and mumps. Influenza A gets amantadine or rimantadine. Relenza and Tamiflu treat influenza A and B. Interferon, a protein, treats hepatitis B and C. Pleconcaril treats the picornaviruses.
Considerations
The topic of a new strain of influenza prompted the development of a second flu vaccine in 2009. Known as H1N1 influenza, the flu caused the Centers for Disease Control to issue a pandemic warning and widespread release of an antiviral aimed at this latest flu strain. The 2009/2010 flu season brought to mind how each strain of flu required individualized and specific treatment, as many people received two inoculations that flu season.
Resistance
As with bacteria, viruses mutate. Especially true of the HIV virus, it also multiplies at an astounding rate. Trying to keep ahead of the virus, infectious disease doctors treat with a triple load of drugs. One type of medicine comes from each of three classes to improve the odds of outsmarting the virus. The trio, while compounding side effects threefold, has had the most effective rates for the longest amount of time.
References
- Fundamentals of Microbiology, 5th ed., I. Edward Alcamo, PhD; 1997
- Centers for Disease Control and Prevention: Antiviral Drugs, 2009-2010 Flu Season
- Microbiology Bytes: Antiviral Drugs
- Microbiology Bytes: HIV 1, Entry, Inhibitors and Resistance
