January 11, 2014 in Features

Ask Dr. K: Some viruses are resistant to anti-viral drugs

Anthony L. Komaroff Universal Uclick
 

DEAR DOCTOR K: What is a virus? And what makes viral illnesses so difficult to treat?

DEAR READER: Viruses are a very simple kind of germ. They are smaller and simpler than other common germs, such as bacteria and fungi. They cause illnesses ranging from mild – like the common cold – to potentially fatal. This includes diseases such as smallpox, influenza, Ebola and HIV.

When viruses infect our cells, they take over a cell’s “machinery.” The cell can’t carry out its normal life-sustaining tasks. Instead, the host cell becomes a virus-manufacturing plant, making viral parts that reassemble into whole viruses and infect other cells. Finally, the host cell dies. Many common viral infections get attacked and eliminated by our immune system. For many of these infections, like those that cause the common cold, we don’t actually have (or need) anti-viral drugs.

Other common infections can be eradicated by the immune system in some people, but not in others. In that latter group, anti-viral drugs can assist the immune system in winning the war and eradicating the virus. The viruses that cause hepatitis B and C are examples.

Still other viral infections have tricks that make it impossible (currently) to eliminate them. Neither our immune systems nor anti-viral drugs can get rid of them, and they remain with us for the rest of our lives. Sometimes they remain “asleep” in our bodies, causing no damage. Other times they periodically awaken and cause symptoms; a cold sore caused by a herpes virus is an example. Anti-viral medicines sometimes can keep them dormant, or make them go back to sleep.

Finally, viruses reproduce so rapidly that they have plenty of opportunity to change their genetic stripes with each new generation. This allows them to develop resistance to whatever drugs or vaccines we throw at them.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.


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