What’s a Virus, Anyway?

From influenza to polio, from dengue to encephalitis, from Ebola to hanta, viruses are the most deadly challenges humans face. And there are uncountable numbers of viruses, most of which we don’t know about. J. Craig Venter, who decoded the human genome, has genetically sequenced 10,000 or so of them. When he sailed his yacht, Sorcerer II, around the world in 2005 and 2006, he stopped every so often to take samples of seawater and then studied what was in them. He found that 1 tablespoon of ocean water contains billions of previously unknown viruses.

Viruses are weird. They are unlike any other self-replicating form that we call life. They have no nucleus and no outer membrane, and they’re tiny — about 1% the size of a single bacterium. They cannot reproduce by themselves, and instead must invade a normal cell and rearrange the molecules they find inside to assemble more versions of them. In the process, they typically kill the cell by exploding its membrane, which is how they kill humans: one cell at a time. But viruses are like cells in that they have genes and can evolve.

Ebola virus

Electron microscope image of the deadly Ebola virus.

The human immune system is good at identifying viruses and killing them by developing antibodies that bind to the viruses and keep them from reproducing, which is why vaccines work. Vaccines educate the immune system about a specific virus and set up the antibody process. Sometimes a vaccine can be as simple as injecting dead viruses into a human so the immune system can build antibodies against it. Killer T cells in the human immune system can identify a virus on a host cell and kill the cell to prevent the virus from replicating.

DNA viruses are very tough to eradicate permanently. They can become latent, maintaining a constant war with the immune system. Chickenpox, Epstein-Barr, shingles and herpes cold sore viruses can “hide” effectively in a human body for decades.

Medicine has almost nothing to fight viruses. A few approved anti-virus drugs have been developed in recent years, but most are not reliably effective, and even then only against a very narrow range of viruses. Antibiotics actually kill bacteria, but anti-viral drugs usually only keep the virus from reproducing or spreading too fast to overwhelm the body.

But several companies have promising antiviral drugs in the works. Gilead Sciences launched Sovaldi in December 2013, and it actually cures hepatitis C in almost all cases. It is not a broad-spectrum anti-viral. There are anti-viral drugs to tackle some flu bugs and herpes, but they don’t work reliably. A “cocktail” of anti-virals can keep HIV at bay for a while.

The most interesting anti-viral drugs in development come from a Raleigh, N.C., company called Chimerix. The company has a broad spectrum antiviral drug called bincidofovir now in a large Phase 3 trial.

To your health and wealth,

Stephen L. Petranek
for The Daily Reckoning

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