Herpes Simplex Virus

Herpes Simplex Virus

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Herpes Simplex Virus

The herpes virus or HSV causes viral diseases of the mouth and genitals in humans. Herpes simplex 1 and 2 are the two strains of the herpes virus and cause infections of the mouth and genitalia respectively. The virus could be inactive for a long period and reactivates later or causes overt diseases. Herpes virus belongs to the enveloped viruses. The virus is enclosed in a membrane that determines its infection potential. Viruses whose membranes are broken cannot cause an infection and can only be infectious when in contact with mucosal membranes of infected individuals. The viral structure also has a tegument, which occurs between the membrane and the capsid. The tegument has enzymes and virally encoded proteins that trigger the infection initiation. On the surface of the virus are receptors, which determine the cells infected by the virus (Hunt, 2010).

HSV-1 causes sores and fever blisters on the face and mouth, also known as oral herpes. It is transmitted through infected oral secretions, which can be passed through kissing, and sharing of utensils and personal items such as toothbrush and lip balm. The symptoms of oral herpes include sore throat, swollen lymph nodes in the neck, fever, burning sensation around the nose and mouth, and small blisters around the mouth area, which are normally painful and fluid-filled. HSV-1 also causes genital herpes although on rare occasions.

HSV-2 causes genital herpes, which is mainly characterized by sores on the groin. The sores could occur on other body parts, but they mainly occur below the waist. The virus is spread through sexual contact when one is exposed to open sores or semen. Mothers living with the virus could pass it to their children at birth if the vagina has open sores at the delivery time. Therefore, expectant mothers should seek medical advice before delivery. Irresponsible sexual behaviors such as unprotected sex and many sexual partners predispose an individual to HSV-2. Other risk factors include existing sexually transmitted diseases, compromised immune system, and being female. Genital herpes manifests itself through symptoms such as sores and itchiness in the genitalia, and pain during urination (Looker, Garnett, & Schmid, 2008).

There is no cure for herpes, but various preventive measures are essential. For example, people should avoid sharing personal items, have responsible and protected sex, wash hands regularly, reduce stress, and avoid kissing and performing oral sex on infected persons. Facial herpes can be prevented by wearing sunscreen to protect the face from direct sun. Factors such as sunlight, menstruation, stress, existing medical conditions, and fever often trigger herpes symptoms. Asymptomatic individuals can spread herpes sans having any visible sores on the body because the virus could be in the latent period. Diagnosis of the disease involves a physical examination of the patient for the symptoms such as sores on the mouth and genitals. Confirmatory tests include herpes culture and blood tests for the HSV-1 and HSV-2 antibodies. Since there is no cure for herpes, doctors can prescribe broad-spectrum antivirals such as acyclovir, valacyclovir, and famciclovir, which can be in the form of creams or pills. The drugs help suppress the symptoms of herpes reducing the cases of outbreaks, and the chances of spreading them to other persons.

Anybody who encounters infected material is at risk of contracting herpes. HSV-1 has been a common occurrence in America since 90% of the population has been in contact with the virus at one time. HSV-2 is prevalent among sexually active individuals since it is spread through contaminated fluid such as vaginal secretions and semen. In sub-Saharan Africa, the rate of infection among men is between 10-50% and 80% among women. The rate in South and Central America is 20% to 40%, which is highest among women. Developing Asian countries have lower prevalence rates than other regions, which range between 10-30% (Looker, Garnett, & Schmid, 2008). In general, 20-30% of all sexually active adults are infected, especially among prostitutes, immunosuppressed individuals, and socioeconomically disadvantaged groups. Genital herpes predisposes infected individuals with HIV/AIDS and it is a leading cause of morbidity. The prevalence rate of herpes is projected to increase if people do not embrace safe and responsible sexual habits and minimize contact with infected individuals. The statistics are estimated to increase in the future unless scientists discover a cure for herpes.

The herpes virus causes infection by binding to the surface of the target cell with the correct receptors. There is a fusion of the virus and the cell membrane at the appropriate pH, which enables the formation of syncytia and cell-to-cell transmission between the infected cells. The nucleocapsid then binds to the nuclear membrane and the genetic material of the virus enters the nucleus of the cell. Alpha, beta and gamma proteins are fundamental to the transcription process that leads to the maturation of the virus. The DNA-dependent RNA polymerase I enzyme transcribes the viral DNA into RNA. The synthesis of the viral RNA determines if the infection is persistent, lytic or the virus becomes latent. The virus then encodes its own DNA and there is an assembly of the virus with the DNA filled nucleus. The virus buds out of the double nuclear membrane or plasma membrane and exits the cell through exocytosis. The virus at this stage is infectious and causes disease in the host (Hunt, 2010).

Prions cause neurodegenerative disorders in both animals and humans, and are known to cause the mad cow disease in cattle. The first disease incidence occurred in 2003, in the United States. The United Kingdom was the first country to report cases of the disease, and 98% of the global cases were reported to occur in the country between 1986 and 2001. The cases continued to increase worldwide with 25% in 2000 and 55% in 2003. However, the prevalence of prion diseases has remarkably reduced over the years. Unlike viruses that multiply inside the host, prions act as templates of abnormally folded proteins when they infect the brain of mammals. The abnormal proteins cause neurodegenerative diseases such as Creutzfeldt-Jakob disease in humans and mad cow disease in livestock and cattle (Weiss, 2004).

References

Hunt, R. (2010). Virology: Herpes viruses. Microbiology and Immunology. Hoboken, NJ: John Wiley & Sons.

Looker, K. J., Garnett, G. P., & Schmid, G. P. (2008). An estimate of the global prevalence and incidence of herpes simplex virus type 2 infection. World Health Organization. Retrieved on 13 April 2014 from http://www.who.int/bulletin/volumes/86/10/07-046128/en/

Weiss, H. (2004). Epidemiology of herpes simplex virus type 2 infection in the developing world. National Center for Biotechnology Information. Retrieved on 13 April 2014 from http://www.ncbi.nlm.nih.gov/pubmed/15115627