Prevalence of Herpes Simplex Virus Type 2 in U.S. Decreasing

It appears the recent trend in the increasing prevalence of herpes simplex virus type 2 in the U.S. has been reversed, with a reported decrease in the number of people with the virus in recent years, according to a study in the August 23/30 issue of JAMA. The prevalence of herpes simplex virus type 1 also decreased, but the incidence of genital herpes caused by this virus may be increasing.

Herpes simplex virus type 2 (HSV-2) is the cause of most genital herpes and is one of the most prevalent sexually transmitted infections worldwide, according to background information in the article. Herpes simplex virus type 1 (HSV-1) is typically transmitted during childhood via nonsexual contact. HSV-1 has emerged as a principle causative agent of genital herpes in some developed countries. Both HSV-1 and HSV-2 can cause infrequent but serious diseases such as blindness, encephalitis (inflammation of the brain), and neonatal (the first four weeks after birth) infections.

Data from National Health and Nutrition Examination Surveys (NHANES) during 1976-1980 (NHANES II) and 1988-1994 (NHANES III) indicated that the overall seroprevalence (the number of persons in a population who test positive for a specific disease based on blood serum specimens) of HSV-2 in the U.S. increased by 30 percent, while the overall HSV-1 seroprevalence was unchanged.

Fujie Xu, MD, PhD, of the Centers for Disease Control and Prevention (CDC) and colleagues examined national trends in HSV-1 and HSV-2 seroprevalence in the 1999-2004 survey compared with the 1988-1994 survey. The analyses included 11,508 persons from the 1999-2004 survey and 9,165 persons from the 1988-1994 survey who were age 14 to 49 years.

The researchers found that the overall age-adjusted HSV-2 seroprevalence was 17.0 percent in 1999-2004 and 21.0 percent in 1988-1994, a relative decrease of 19.0 percent between the 2 surveys. Decreases in HSV-2 seroprevalence were especially concentrated in persons aged 14 to 19 years between 1988 and 2004. Among those infected with HSV-2, the percentage who reported having been diagnosed with genital herpes was statistically different (14.3 percent in 1999-2004 and 9.9 percent in 1988-1994).

The authors write that the reasons that HSV-2 seroprevalence significantly decreased even after accounting for changes in measured sexual behaviors may include a combination of unmeasured factors, such as careful partner selection, condom use, and/or choosing oral sex over vaginal sex.

Seroprevalence of HSV-1 decreased from 62.0 percent in 1988-1994 to 57.7 percent in 1999-2004, a relative decrease of 6.9 percent between the 2 surveys. Among persons infected with HSV-1 but not with HSV-2, a higher percentage reported having been diagnosed with genital herpes in 1999-2004 compared with 1988-1994 (1.8 percent vs. 0.4 percent, respectively).

The researchers add that a decrease in HSV-1 seroprevalence in the United States is not unexpected due to improvements in living and hygiene conditions.

The ability to monitor HSV-1 seroprevalence along with HSV-2 seroprevalence in NHANES is important for the development of HSV-2 prevention strategies, such as those related to vaccination. The changes in HSV-1 and HSV-2 seroprevalence will also directly affect the cause of neonatal herpes. Future studies are needed to monitor the changing HSV-1 and HSV-2 trends and to develop effective strategies to prevent HSV infection, the authors conclude.

Reference: JAMA. 2006;296:964-973.

Source: American Medical Association