Herpes simplex virus: epidemiology
herpes simplex virus
HSV or Herpes simplex virus causes a transmissible infection that affects about 60-95% of adults worldwide. The two types of the virus (HSV-1 and HSV-2) primarily infect humans. HSV-1 is mainly associated with infections of the oral area, specifically the mouth, pharynx, eyes, face, and CNS (central nervous system), and HSV-2 is mainly associated with infections of the anogenital region, although both serotypes can infect any body. Go.
Epidemiology
Most adults have HSV and carry latent virus, but the severity of symptoms, serotype, and mode of transmission vary by age. Children are primarily infected with orolabial HSV-1 by age five, with infection rates of 33% in populations of lower socioeconomic status and 20% in people of higher socioeconomic status. In adulthood, HSV-1 affects 70-80% of the population of lower socioeconomic status, as well as 40-60% of the population of higher socioeconomic status. The occurrence of HSV-1 increases consistently with age, at the age of fifteen, reaching 40% and increasing to 60-90% in older adults.
In the US, the occurrence of HSV-1 increases steadily with age, from 26.3% in children 6 to 7 years old and 36.1% in children 12 to 13 years old to 90% in people older than 70 years. Take note that the overall occurrence of HSV-1 in the US has been shown to be decreasing over time.
In general, the incidence of HSV-1 infection is higher than that of HSV-2 in most geographic areas. HSV-2 is primarily sexually transmitted and therefore not as common in children. However, HSV-2 can be transmitted from mother to child during pregnancy, with an incidence of 1/3,000 to 1/20,000 live births and about 1,500 new cases per year in the United States. About 2% of women get genital herpes during pregnancy, and about 20-30% of pregnant women are HSV-2 seropositive.
The occurrence of HSV-2 varies by age, sex, and country. The occurrence of HSV-2 is highest in parts of South and Central America and regions of sub-Saharan Africa. The incidence is usually lower in southern and western Europe than in northern Europe, as well as in North America. Asia has the lowest occurrence rates of HSV-2.
The incidence is lower in men than in women. However, the incidence increases with age from low levels in children under 12 years of age to 20-40% at age 40 years and as high as 80% among populations at increased risk.
In the US, the incidence of HSV-2 infection in African Americans is higher than in Mexican Americans or whites. Although time trends in the prevalence of herpes simplex are limited, most studies indicate that the incidence of HSV-2 has increased in recent years in countries such as the US. In other populations, the occurrence of HSV-2 has remained constant or has decreased.
As noted above, HSV-2 is primarily associated with infections of the anogenital region, whereas HSV-1 is found extragenitally. However, recent investigations have shown a 30% increase in the prevalence of HSV-2 infection, with HSV-2 being as common as HSV-1 in extragenital areas but in the orofacial region. In addition, HSV-1 appears to be increasing in occurrence in the anogenital region, previously known to be primarily HSV-2 infected.