Behavior: Battling an Elusive Invader

The herpes virus perplexes researchers and defies a cure

By any measure, herpes is an extraordinary bug. "It is the ultimate parasite," declares University of Michigan Microbiologist Charles Shipman. Says Washington, D.C., Urologist Peter Gross: "If you were doing a science-fiction movie, you couldn't invent something better than herpes." What makes it unique is that unlike influenza and other viruses, it survives in the human body. long after an attack has subsided. Once herpes has found its way into your system, says Dr. Harold Kessler, a Chicago specialist in infectious disease, "it's your virus for life."

This perplexing persistence is characteristic of all five members of the human herpes family. After herpes simplex 1 and 2, the best known is the varicella-zoster virus, the cause of chicken pox, the nation's third most common ailment. Three-quarters of the U.S. population gets chicken pox by age 15. Most are never bothered by the virus again, though it will linger in their nervous systems for the rest of their lives. Some will not be so lucky. They will be victims of shingles, a painful, blistering rash that is triggered in adults when, for reasons unknown, the varicella-zoster virus reawakens.

Cytomegalovirus (CMV), another type of herpes, infects up to 80% of the U.S. popula tion, and nearly 100% of male homosexuals. Though not usually a problem for adults, CMV can be deadly to cancer patients and others whose immune systems have been suppressed by drugs. It also causes a wide range of birth defects and is the most common cause of infectious retardation in infants. Epstein-Barr virus is the herpes associated with mononucleosis. More tragically, it is believed to contribute to Burkitt's lymphoma, a cancer that mainly strikes Africans.

Herpes simplex is almost always transmitted by intimate contact between infected and noninfected skin surfaces. This does not necessarily mean sex. Notes Kessler: "If a mother has a cold sore, she shouldn't be kissing her children or anyone else." Once inside, herpes reproduces by taking over the protein-producing apparatus of the host cell. Gross calls it "a biological coup d'état."

Once the attack has been brought under control by the immunological system, the virus retreats. In oral herpes, which is generally caused by herpes simplex Type 1, it travels through nerve fibers into the trigeminal ganglia, a group of nerve cells located near the brain. In genital herpes, usually caused by Type 2, the virus withdraws to the sacral ganglia, nerve cell clusters near the spinal cord. Lodged in the nerve cells, the herpes simplex virus is beyond the reach of the body's immune system and enters a latent stage. This stage may last forever, or it may be broken when the virus reawakens and reinfects the original site. Such recurrences may take place as often as twice a month or as rarely as once a decade.