If I Have Cold Sores (HSV1) Am I Protected Against Genital Herpes (HSV2)?

Girl with cold sore
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Question: If I Have Cold Sores (HSV1) Am I Protected Against Genital Herpes (HSV2)?

Answer:  No.

There has not been a lot of published research discussing whether or not infection with HSV-1 (usually associated with oral infection) provides any protection against HSV-2. (HSV-2 is usually associated with genital infection). However, what research there is suggests that infection with one strain of the herpes virus is NOT protective against infection with the other.

In other words, if you have cold sores you can still get genital herpes... and vice versa. 

One study that was designed to directly research the question found that HSV-1 infection was not protective against HSV-2 infection. Individuals with HSV-1 were just as likely to acquire HSV-2 as their HSV-1 negative counterparts. However, a previous oral herpes infection did increase the likelihood of a newly acquired genital herpes infection being asymptomatic. In other words, when people with cold sores were infected with genital herpes, they were less likely to have any symptoms. This makes sense. Research clearly shows that many people are infected with both strains of the virus. In addition, it is possible to transmit either of the two herpes viruses to their less preferred sites during oral sex. In fact, HSV-1 is accounting for more and more cases of genital herpes as time goes on.

That was a study of oral infection with HSV-1.

However, genital HSV-1 infection also doesn't protect you from HSV-2 infection. A 1998 study published in the Journal of Infectious Diseases conclusively demonstrated that it is possible for someone to be super-infected with HSV-2 after already being infected with HSV-1. (A "super infection" occurs when someone gets infected with a different strain of a virus they are already infected with.)  Such a new infection may show up as a change in outbreak frequency.

This is because it is possible for a person to have separate genital outbreaks of HSV-1 and HSV-2 at different times. However, the only way to distinguish between the two types of outbreaks is through visiting a doctor for a viral culture. HSV-1 and HSV_2 outbreaks can not be clearly distinguished by symptoms alone.

In short, cold sores don't protect against genital herpes. That's why it's very important to practice safe oral sex. This is particularly true if you have a partner with cold sores. However, many people have unrecognized herpes infections. Therefore, using barriers for oral sex is a good idea in general. In addition, it's good to be aware that people can transmit herpes even when they don't have symptoms. Therefore, the absence of a cold sore or genital lesion is not a guarantee of risk-free sex.  

Sources:

Langenberg A.G.M. et al. "A PROSPECTIVE STUDY OF NEW INFECTIONS WITH HERPES SIMPLEX VIRUS TYPE 1 AND TYPE 2" New England Journal of Medicine. 1999;341:1432-8.

Löwhagen GB, Berntsson M, Bonde E, Tunbäck P, Krantz I. Acceptance and outcome of herpes simplex virus type 2 antibody testing in patients attending an STD clinic--recognized and unrecognized infections. Acta Derm Venereol. 2005;85(3):248-52. 

Haddow L.J. et al. "Increase in rates of herpes simplex virus type 1 as a cause of anogenital herpes in western Sydney, Australia, between 1979 and 2003." Sex Transm Infect. 2006; 82(3):255-9.

Sucato G., Wald A., Wakabayashi E. , Viera, J. & Corey L. "Evidence of Latency and Reactivation of Both Herpes Simplex Virus (HSV)-1 and HSV-2 in the Genital Region" J Infect Dis. 1998; 177 (4): 1069-1072.

Woestenberg PJ, Tjhie JH, de Melker HE, van der Klis FR, van Bergen JE, van der Sande MA, van Benthem BH. Herpes simplex virus type 1 and type 2 in the Netherlands: seroprevalence, risk factors and changes during a 12-year period. BMC Infect Dis. 2016 Aug 2;16:364. doi: 10.1186/s12879-016-1707-8.

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