The rate of viral shedding decreases rapidly during the first year in people with genital HSV-1 infections

The rate of viral shedding decreases rapidly during the first year in people with genital HSV-1 infections

People with a genital infection with herpes simplex virus type 1 (HSV-1), which usually causes cold sores, often shed the virus in the first few months after infection, increasing the risk that they will transmit the virus to sexual partners during this time.

But the excretion rate decreases in the first year, researchers at the University of Washington (UW) School of Medicine in Seattle have found.

The results suggest that genital HSV-1 infection is quite different than genital HSV-2 in that it is significantly less severe in terms of both recurrence and shedding. With HSV-2, we continue to see high excretion rates many years after the initial infection.”

Dr. Christine Johnston, associate professor of allergy and infectious diseases

Johnston was the lead author on paper published Oct. 22 by JAMA.

Historically, HSV-1 has been primarily associated with blisters and ulcers on the lips, often called cold sores or cold sores, and herpes simplex virus type 2 (HSV-2), a closely related virus, has been primarily responsible for genital herpes. But that has changed in recent decades, and today HSV-1 is the leading cause of new genital herpes infections in many parts of the world.

In recent decades, fewer people have been infected with HSV-1 in childhood, making them vulnerable to infection when they become sexually active.

Most genital herpes infections are acquired without symptoms. But when symptoms do occur, they can often include painful blisters and genital sores, fever, chills, fatigue, muscle aches and other flu-like symptoms. Infections can also cause emotional distress, as patients feel the social stigma associated with infection and worry about transmitting the virus to their sexual partners and, if they give birth, to their newborn.

In the new study, Johnston and colleagues sought to better understand the course of genital HSV-1 infections and the immune system's response. Although HSV-1 is known to cause genital symptoms less frequently than HSV-2, this was the first study to comprehensively examine oral and genital HSV-1 excretion using the highly sensitive polymerase chain reaction (PCR) test.

They enrolled 82 men and women who had been diagnosed with their first episode of genital HSV-1 infection. Fifty-four (66%) were women and 28 (34%) were men. Their ages ranged from 16 to 64 years, with an average age of 26 years. Antibody studies showed that about half of the participants had previously been infected with HSV-1.

To detect shedding, participants swabbed their mouths and genitals daily for 30 days, two and 11 months after their first genital HSV-1 episode. The swabs were tested for the presence of HSV-1. Blood samples were also taken at several points during the study to analyze the participants' immune response to the infection. Enrollees took an antiviral medication to treat their first episode but agreed not to take any treatments to suppress the virus during the periods when samples were collected.

The number of days participants lost virus varied. Some participants did not shed any virus at all, but shedding was relatively common after two months, with participants shedding HSV-1 on 12% of days. However, after 11 months the rate had fallen to 7% of days. In most cases, participants had no symptoms despite shedding the virus.

Participants who eliminated at least 10% of the days after 11 months continued swab testing for an additional 30 days two years after their first genital infection. In this group, the excretion rate fell even further to 1.3% of days. Although the sample size was small, the rates are significantly lower than for HSV-2, for which shedding occurs on approximately 34% of days in the first year and remains on 17% of days after 10 years. Parallel to excretion, recurrences occurred rarely, with an average of one recurrence in the first year of infection.

“I think patients can feel reassured that they are likely to have less hair loss and a lower risk of transmitting the virus with a genital HSV-1 infection than with an HSV-2 infection,” Johnston said.

Analysis of the viral samples and the participant's immune response to the infection did not explain why clearance rates differed between participants. But hair loss was more common in those who had a newly acquired infection.

Patients who lack antibodies for HSV-1 and -2 when they are diagnosed with their first case of genital herpes should be advised to expect more frequent hair loss, Johnston said, and may be candidates for suppressive antiviral therapy in the first year of infection.

And although herpes is rare in newborns, it can be devastating, she added. The finding that hair loss is common in the first few months after infection highlights the importance of identifying pregnant individuals at high risk of becoming infected with HSV-1 so that preventive measures can be taken to avoid infection.

Source:

UW Medicine

Reference:

Johnston, C., et al. (2022) Viral shedding 1 year after first episode genital HSV-1 infection. JAMA. doi.org/10.1001/jama.2022.19061.

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