Herpes Simplex Virus (HSV)

Causative Agents

Herpes simplex viruses (HSV), a member of Herpesviridae, are complex (containing ~35 virion proteins) DNA viruses, 180-250nm in size, with genomes up to 235kbp DNA. İnfections caused by two types of HSV (HSV-1, HSV-2) are very common worldwide. Herpes simplex virus type 1 (HSV-1) primarily causes face,eye, mouth, throat, and CNS-central nervous system- infections while HSV-2 is the main causative agent of genital herpes. [1]

Epidemiology

Herpes simplex virus (HSV) infection is one of the most common viral infection with worldwide rates of 65% to 90%. Large differences in HSV-1 and HSV-2 seroprevalence are determined across the Europe, HSV-1 seroprevalence is high in Bulgaria and Czech Republic and lower in Belgium, Netherlands  and Finland. Young adults in Northern European countries are less likely to be infected with HSV-1. HSV-2 seropositivity is widely distributed in Europeans older than 12.  Bulgaria has a high  incidence relative to other European countries such as Germany, Finland, Belgium, Netherlands. [2],

Modes of Transmission

HSV is spread by contact, as the virus is shed in saliva, tears, genital and other secretions, by far the most common form of infection due to a kiss given to a child or adult from a person shedding the virus. While HSV-1 is usually transmitted orally during childhood, HSV-2 is primarily a sexually transmitted infection bu both may be transmitted vertically during chilbirth. The risk of infection to a non-immune individual in contact with contaminated secretions can be as high as 80%. Even tough most of the people  infected with HSV develop labial or genital lesions, the majority are either undiagnosed or without physical symptoms and thus considered at high risk for spreading HSV as they are unaware of their infection. [3], [4]

Diagnosis

Two general approaches; physical examination and laboratory tests are used for diagnosing genital herpes. Altough  testing the virus physically by just looking at a lesion or sore is useful in practice, it doesn’t give an accurate diagnosis as other infections can look like herpes and makes it necessary the confirmation of laboratory tests. Culture tests, antigen detection and serological tests based on antibody detection and HSV Fluorescent Antibody Test (HSV FA ) are the most common tests used in routine.  Culture tests reguire presence of lesion and serological tests need time for antibody to develop. Molecular detection of HSV overcome the drwabacks of other tests. İt is the most accurate test as with real time PCR technology, it is able to detect even tiny amounts of virus in only about 4 hours by also allowing to provide genotypic identification with high analytical sensitivity. [5], [6]

Annotated Bibliography

  1. 1-Chayavichitsilp P, Buckwalter JV, Krakowski AC, Friedlander SF (April 2009). "Herpes simplex". Pediatr Rev 30 (4): 119–29; quiz 130

  2. 2-Pebody RG, Andrews N, Brown D, et al. (2004). "The seroepidemiology of herpes simplex virus type 1 and 2 in Europe". Sex Transm Infect 80 (3): 185–91.

  3. 3-Gupta R, Warren T, Wald A (2007). "Genital herpes". Lancet 370 (9605): 2127–37.

  4. 4-Corey L, Wald A (2009). "Maternal and Neonatal Herpes Simplex Virus Infections". New England Journal of Medicine 361 (14): 1376–85.

  5. 5-Medical Microbiology. 4th edition,Baron S, editor,Galveston (TX): University of Texas Medical Branch at Galveston; 1996.

  6. 6-Diagnosis of Herpes Simplex Encephalitis: Application of Polymerase Chain Reaction to Cerebrospinal