Anyone with genital herpes (HSV-2) ‘sheds’ the virus from their genitals. This means the virus ‘babies’ are released and expelled from the cell the virus resides in. This is a form of replicating, and once it’s completed, the virus is likely to leave the cell, and find a new cell with more resources.
A large study found that people carrying the genital herpes virus can infect a sexual partner 10 per cent of the time. This is high enough that it’s worth understanding viral shedding, and how it can infect your sex partners.
The research into herpes shedding
The researchers collected genital swabs every day from nearly 500 people known to be infected with herpes simplex virus type 2 (HSV-2). About 18 per cent thought they were not infected, but found out they were herpes carriers via blood tests. Most people don’t know they have herpes because they don’t get genital sores or do not notice the sores because they are so small and unobtrusive.
Herpes carriers – those without symptoms at all – shed infectious virus 10 per cent of the 30 or more days they were in the study. Almost all the time, these carriers didn’t have any sign at all of their herpes infection, but were actively shedding live virus.
Herpes carriers that don’t experience symptoms shed the herpes virus only about half as often as those with herpes symptoms. When shedding, however, all carriers shed just the same amount, unless they are having an active herpes outbreak, in which case the outbreak causes a higher level of infectiousness.
It’s impossible to tell if someone is actively shedding virus, so knowing if you are infected at all is important. This can be done via a quick blood test.
What the researchers found:
- Men and women shed the virus exactly the same amount
- Men can shed infectious virus through normal-looking skin on the genitals – the virus is inside skin cells
- Infection with HSV-1 does not make someone shed HSV-2 more or less often
- We don’t know how much shedding it takes to infect another person, but we think it is a ‘relatively moderate shedding episode’
- Those with eight or more genital herpes outbreaks per year shed infectious virus 31 per cent of the time, and people with one to seven outbreaks per year shed infectious virus 19 per cent of the time
Tronstein E, Johnston C, Huang M-L, et al. Genital Shedding of Herpes Simplex Virus Among Symptomatic and Asymptomatic Persons with HSV-2 Infection. JAMA : the journal of the American Medical Association. 2011;305(14):1441-1449. doi:10.1001/jama.2011.420.