Most of the people who are terrified of catching herpes already have it. Herpes -- which has been dubbed "the epidemic of the '80s" -- is one of the most common viruses known, causing a wide range of illnesses from chicken pox to cold sores. Highly publicized cases have caused panic in communities across the country recently, the latest involving a 3-year-old Anne Arundel County child.

But virologists and public health experts say that while concern over herpes is warranted, hysteria is not.

"The whole thing is blown way out of proportion," says Dr. Henry Balfour, director of clinical virology at the University of Minnesota Health Sciences Center and author of the new book "Herpes Diseases and Your Health."

"The most important thing to keep in mind is that herpes simplex is very hard to catch," Balfour says. On a 10-point scale of contagiousness, he says, measles would be a 10, influenza a 5 or 6 and herpes "right down there at the bottom."

Although difficult to catch in any given instance, herpes is widespread, Balfour says, because most people have been exposed to it repeatedly -- mainly from close contact with family members.

"I don't see anything wrong with people being concerned about communicable disease," says Dr. Ebenezer Israel, Maryland's state epidemiologist. "But a good number of people already are infected with herpes, and most of them don't even know they have it.

"Ninety percent of your readers have very likely been infected with a herpes virus already."

Herpes is a family of stubborn viruses infecting people of all ages with a variety of illnesses ranging from mild to life-threatening. Recent media attention has focused on herpes simplex, which can cause cold sores or fever blisters on the mouth and lips (Type 1) or on the genitals (Type 2).

Herpes simplex is such a varied virus that Balfour suggests it might be appropriately renamed "herpes complex."

But unlike measles or flu, neither oral nor genital herpes virus is airborne, which means they cannot be contracted by merely being in the same room with an infected person. Nor can the virus survive outside a living cell, so it is rarely spread by touching toys or furniture or, despite popular belief, a toilet seat.

"You only get it from direct person-to-person contact," Balfour says, "and bad hygiene."

Even with direct physical contact, he says, the virus sometimes will not spread, because the skin itself acts as a protective barrier. But any break in the skin -- a cut, abrasion or rash -- permits spread of the herpes virus through contact with an active cold sore or lesion. Genital herpes is spread primarily by sexual relations.

The child in the Anne Arundel case reportedly has skin lesions on his back and hands. The boy has not been tested to determine which type of herpes simplex he has. Neither his parents nor his two siblings have active herpes, and it is not known how he contracted the virus.

Parents of the boy's classmates kept their children home from school last week for fear the children would catch herpes. But a county judge ruled Wednesday that the boy be allowed to attend school as long as the lesions appear on parts of his body covered by clothing. And doctors cautioned that concerned parents and teachers should not overreact to the risk of herpes spreading from an infected schoolchild.

"The likelihood of transmission is low," says Dr. Joseph Bellanti, director of the immunology center at Georgetown Medical Center. Many children -- up to 50 percent by some studies -- already harbor the herpes virus in their throat secretions, he says.

"I don't mean to minimize the seriousness of herpes," Bellanti says. "It can be a serious disease. But 99 percent of the infections that occur with herpes are clinically not noticeable" -- there are no symptoms. The herpes virus is what Bellanti calls "an opportunistic infection." It invades a cell, then migrates along nerve fibers and hides inside bundles of nerve cells called ganglia, lying dormant near the brain or spinal cord.

Then, for reasons not fully understood, in some people the virus reawakens and moves back down the nerve endings to the skin, causing painful cold sores or genital lesions.

Only in this stage, when cold sores are active and the virus is "shedding," is herpes infectious. And even then, it spreads only by direct person-to-person contact with the infected sore.

A recurrence can be triggered by any of numerous factors, including fatigue, emotional stress, sun exposure and skin abrasions. Patients treated with drugs that suppress the immune system -- for example, cancer patients or recipients of organ transplants -- also are vulnerable to herpes infections. BB ellanti attributes the public's often-hysterical fear of herpes to a general fear B of the unknown, compounded by herpes' association with venereal disease and sexual relations. Although herpes has become a household word, misunderstanding and confusion about the virus persist.

"If Vietnam was the first television war, herpes is the first television epidemic," writes virologist Balfour in the preface to his book.

In people without symptoms, evidence of a herpes infection, past or present, can be detected by the presence of antibodies -- disease-fighting proteins -- in the blood.

"It's an extremely common virus," says epidemiologist Israel. "If you're an adult and you don't have the antibody, that's news."

He urges parents concerned about the case of herpes in Anne Arundel County to keep the relatively small risk in perspective.

"The long and the short of it," he says, "is if you're a child in that school, you have as much chance of catching herpes from the community as from that particular child."