Cold sore virus increasing cause of genital herpes and ‘strongly associated’ with early start to sex

Genital herpes due to HSV-1 – the herpes simplex virus primarily associated with cold sores on the mouth – is strongly associated with an early start to sex, suggests research in Sexually Transmitted Infections. And its prevalence is increasing, say the authors.

The findings are based on blood samples and details of sexual behaviour from 869 people attending a central London sexual health clinic and from 1494 blood donors.

Analysis of the samples showed that evidence of previous or current HSV-1 infection was found in 60 per cent of clinic attenders and 46 per cent of blood donors.

But the analysis also showed that the prevalence of HSV-1 was strongly related to sexual behaviour, especially the age at which first sex took place. Among clinic attenders, a 20 year old was over 60% less likely to have HSV-1 than someone who started having sex for the first time at the age of 15. And among blood donors, a 20 year old was 36 per cent less likely to be infected with HSV-1.

The authors point out that the proportion of genital herpes due to HSV-1 infection is rising in the UK, especially among the young, but that childhood acquisition of the virus is falling. They say that several UK centres now report that primary genital HSV-1 is now the most common cause of genital herpes in young women.

HSV-1 can be passed on through kissing someone with a cold sore or through oral sex, and potentially through penetrative sex, say the authors. HSV-1 infection is no guarantee of protection against HSV-2 infection, and furthermore, genital infection with HSV-1 could mean subsequent genital HSV-2 infection that is likely to recur.