People Can Spread Herpes Easily, Even When Free Of Symptoms

Warning: This post is going to be a little icky. There will be talk of genital herpes and shedding of viruses that can infect sexual partners. Stop now, if that's not your cup of tea.

For the rest of you, on with the post.

Researchers at the University of Washington have found just how easily people infected with herpes simplex type 2 virus, which causes genital herpes, can unknowingly pass it on to other people.


This isn't trivial. The HSV-2 virus is one of the most common sexually transmitted infections in the world. In the U.S., 16 percent of adults test positive for HSV-2 infection.

Only a minority of them — about 10 percent to 25 percent — show outward signs of infection. And most people get infected with HSV-2 from people who don't have a "clinical history of genital herpes," as the authors of a study just published online by JAMA delicately put it.

So somebody doesn't have to have oozing sores to pass the virus along.

The University of Washington researchers gathered some detailed information on that. They found 410 people with symptomatic genital herpes and 88 who tested positive for infection but showed no signs of it. Each person used a swab to collect "genital secretions" each day. They also kept a diary of symptoms.

Long, tough-to-tell story short, people with herpes that manifested with sores were twice as likely to shed contagious amounts of virus particles as infected people without symptoms. But in the study, which lasted about two months for each person, genital herpes virus was detected at least once in 68 percent of those free of symptoms. For symptomatic people the figure was 83 percent.

There are some more gruesome details, but the upshot is that unrecognized infections with HSV-2 are a big source of transmission of the virus to new people.

The authors conclude:

The issue of infectivity is both a patient management and a public health concern. The primary concern of many HSV-2–seropositive persons is the risk of transmission to sexual partners; in our experience this is the main source of angst in patients with genital herpes.

Once someone is aware they're infected with HSV-2, they can take steps, such as using condoms and taking the antiviral drug valacyclovir, to reduce the risk of transmission.

But not very many people without symptoms know they have the virus, and testing for it isn't routine, as the authors point out.