"These recent figures show that infection is around five times more common than we previously thought," says Dr Raj Patel, consultant in genito-urinary medicine at the Royal South Hampshire Hospital in Southampton. "We were aware of the people seriously enough affected to seek help, but they represent only about 20 per cent of the total number infected. Given this new evidence, doctors are urgently debating how best to reduce the spread of the disease."
Over the past 10 years, genital herpes has, unsurprisingly, been overshadowed by fear of Aids. But although it is not fatal, herpes can cause great discomfort. Concern about giving the disease to others can destroy sex lives, as the case histories below demonstrate. Typically, inflammation of part of the genitals is followed by the appearance of small ulcers, which heal over a period of a week or so. The frequency of attacks varies greatly from one person to another, but the disease can recur as often as once a month.
Many people identified by blood test as carrying the virus say they are not aware they have genital herpes. In some, this is probably because the symptoms caused by the disease are slight enough to be misinterpreted as chafing by tight underwear or intercourse. Others may genuinely have no symptoms at all.
The fact that the disease can be mild is encouraging for some. On the other hand, people who have few problems themselves may cause major problems in others by spreading the disease unwittingly. There is no way of telling how serious herpes will be in a newly infected person. And, once the virus is present, it is there for life.
Dr Larry Corey and colleagues at the University of Washington, in Seattle, recently asked a group of women with herpes to take a swab from their genitals every day for 10 weeks. Sensitive methods of detection showed the virus was frequently present even on days when the women had no symptoms. Doctors have not yet proved that this asymptomatic shedding of virus is sufficient to be infective, but many believe it is.
"We have known for years that more than half of all herpes transmission occurs from people who have not been diagnosed as having the disease or from people who have no symptoms at the time of intercourse," warns Dr Patel. "This new American research may show why."
Nevertheless, not all recent findings about herpes are gloomy. "It is true that we do not have a pill that will kill the virus stone dead," says Dr Simon Barton, a consultant at London's Chelsea and Westminster Hospital. "But the severity of an attack can be significantly reduced if people start taking the antiviral drug acyclovir as soon as they become aware that a recurrence is imminent. And perhaps a third of them can abort attacks entirely."
Studies have also confirmed that people who suffer more than six herpes episodes per year benefit by taking acyclovir continuously. With such suppressive therapy, up to 90 per cent remain free of attacks over a year. "The original studies involved people with frequent herpes episodes, but anyone whose psychosexual health is appreciably affected by the disease should be offered such continuous therapy as part of their care," says Dr Barton.
There is another potentially exciting side to suppressive therapy. Dr Corey's Seattle labs have discovered that continuous use of acyclovir can reduce the rate at which the virus is shed from the genital tract even during periods between attacks. If this reduction in asymptomatic shedding can be confirmed, and if people carrying the virus can be identified, we may have a way of reducing the spread of the epidemic.
Another possibility is use of a vaccine. We are familiar with the idea that vaccination prevents people from acquiring an infection. But it seems that vaccines can also boost the immune response of people already infected by the herpes virus, so reducing the severity of the disease. A study published last year in the Lancet showed vaccination cut the frequency of herpes episodes by a quarter. New vaccines under development should improve on this figure.
"But the most important goal is to reduce the infectivity of people carrying the herpes virus," says leading vaccine researcher Dr Stephen Straus, of the American National Institutes of Health. It will be some time before we know whether vaccines can achieve that aim, but Dr Straus and colleagues think the strategy worth pursuing.
"At the moment, though, the best advice we can give is that condoms should be used all the time, and not just when there are symptoms of genital herpes," says Dr Patel. "The virus can be transmitted to areas not covered by the condom and spread can occur through oral-genital contact. But condoms are the best current option for reducing the risk of disease."
In the United States, some estimates suggest that 45 million people - one in four of the adult population - already carry the herpes virus. This is double the number of 10 years ago. According to Dr Mike Reitano, a New York-based specialist in the disease, if we do not soon find an effective way of stopping the spread of herpes, the question of transmission will simply go away - because everyone will have it. The situation in the UK is not yet as serious, but it may become so unless we are able to develop new means of tackling the problem.
He had the fling, now she has the disease
Anne, 33, caught herpes from her husband following his four-month affair with another woman. That was six years ago. She had two attacks within the first few months but chose to do nothing about the problem during the period she was without a sexual partner, following the break-up of the marriage. Anne is now seeing someone but is anxious about any physical involvement. She has started drug treatment to suppress any new attacks and has told her potential sexual partner about the risk of transmission.
Fear of transmitting it made John give up sex
Since he caught the disease three years ago at the age of 25, genital herpes has come to dominate John's life. The source of infection was a woman he had been sleeping with for 18 months. She did not know she had the disease, attributing her occasional minor symptoms to thrush. In the year after their relationship ended, John had nine severe attacks. Even though he consistently used condoms, the fear of transmitting the disease to new partners eventually led him to give up sex. A hospital clinic prescribed acyclovir, and this reduced the frequency and severity of herpes episodes, but John's treatment was stopped for a period by his GP, who said he had brought the problem on himself. John is now back on hospital-prescribed acyclovir but still has a mild attack every three months.
Chances are she has the virus - just no symptoms
A casual sexual contact in Spain infected Andrew, 26, in 1986. He has three mild attacks a year, each preceded by two or three days of tingling sensations on the part of the penis that develops ulcers. He has now married. Knowing the risk of transmission, he and his wife made the informed choice to use condoms before and during any attack. Despite this, the chances are that she will have been infected by the virus, but she has no symptoms. They feel the disease has had no significant impact on their lives.