Dear Dr. Jeff: Can you have genital herpes and not know it? Can a person infect you with herpes, even if they've never had any sores? —L.H.

Dear L.H.: Unfortunately, the answer is yes to both of those questions.

There are two strains of herpes virus, type 1 and type 2. Type 1 causes nearly all oral herpes infections ("fever blisters" or "cold sores"), and probably 40 percent of genital herpes infections (through oral sex). Type 2 causes about 60 percent of genital herpes infections, and a very small number of oral infections.

About 80 percent of the population has had, at some time, oral herpes. The prevalence of genital herpes has increased significantly over the last 25 years, with more than 20 percent of adolescents and adults in this country estimated to be infected. Among college students, the prevalence is thought to be even higher.

The "classic" signs of an initial genital herpes infection are grouped blisters or sores in the genital area. The sores usually itch or burn or hurt, and are often accompanied by flu-like aches and pains and a low-grade fever. After the initial infection, the herpes virus lies dormant in nerve bundles at the base of the spine. The virus periodically reactivates, traveling back down the nerve bundle and causing a recurrent outbreak.

Recurrent outbreaks are usually milder and briefer, and typically occur four to five times per year. They are frequently triggered by other illnesses, poor diet, or emotional or physical stress. Over time, recurrent outbreaks become less frequent and less severe, and usually eventually cease altogether.

It has become clear, however, that most cases of genital herpes do not present with "classic" signs and symptoms. In fact, up to 60 percent of infections are not recognized by patients nor diagnosed by clinicians, because they do not cause the typical sores. An additional 20 percent of infections cause no symptoms whatsoever.

Transmission of herpes occurs most readily from skin-to-skin contact with an actively, broken-out site. Most skin on our bodies is too thick for the virus to penetrate, but mucosal surfaces (oral and genital) are quite susceptible. Fortunately, the virus is very fragile, and does not live long on inanimate surfaces. So herpes cannot be transmitted by contact with a toilet seat, bathtub, or towel.

Herpes virus is shed in huge numbers during outbreaks. It can also be shed in between outbreaks, when there are no signs or symptoms. This asymptomatic shedding is thought to occur only a few days per year. But because most people naturally tend to avoid sex when they have active sores, most transmission of herpes?in fact over 70 percent?is thought to occur in the absence of warning signs or symptoms.

Herpes is diagnosed most reliably by culturing the virus from active lesions. Diagnosis is more problematic in between outbreaks, or in an asymptomatic carrier. Blood tests can be done to measure antibodies to both viral types, but they are not always accurate. Interpretation of test results can be difficult, because, as noted earlier, neither HSV-1 nor HSV-2 is anatomically restricted.

If at some time 80 percent of the population has had oral herpes, for instance, then 80 percent of the population can be expected to have antibodies to HSV-1, whether or not HSV-1 is also the cause of an additional genital infection. While positive HSV-2 antibody titers indicate that it is likely that the individual has had genital herpes, the results are similarly not definitive.

Many people who have been diagnosed with genital herpes find it emotionally and psychologically distressing. Fortunately, for most, this distress and anxiety fade with time. Genital herpes rarely leads to other health problems, with the very important exception that it increases the risk of sexually acquiring and transmitting HIV.

There is at present no cure or vaccine for herpes. There are three medications that will help speed healing in both initial and recurrent outbreaks. All three can also be taken daily and long term, to prevent recurrences. It is very likely that daily medication decreases, if not largely prevents, asymptomatic viral shedding.

All of this means that safer sex practices remain the key to decreasing herpes transmission. Avoiding intimate contact when sores are present, is an obvious place to start. In between outbreaks, using condoms, dental dams, or female condoms significantly lowers the risk of viral transmission.

Of course, no safer sex practices can eliminate all infectious risks. But being informed about those risks is a critical first step.

Be well, be thoughtful, and be safe!

Jeff Benson, M.D.
Dudley Coe Health Center