Author

Cindy Dubs, Biology 230 Section CRA, Spring 2010

Disease

Herpes Simplex Virus Infections

Causative Agents

Herpes Simplex Viruses (HSV) are enveloped, double-stranded linear DNA viruses that have an icosohedral (def) capsid and belong to the family of Herpesviridae. The virus ranges in size of 150-200 nanometers (def). The virus is know to affect humans and can affect any range with the majority of infections occurring between childhood and adolescence.

There are two known types of HSV – Herpes Simplex Virus Type 1 (HSV-1) and Herpes Simplex Virus Type 2 (HSV-2). Type 1 strains most often infect the oral cavity resulting in oral herpes, better known as cold sores. Type 2 strains are most often known to cause genital herpes. There has been research to show that either strain could cause herpes in either location, the oral cavity or genitals.

Epidemiology

Herpes Simplex Virus is a very common viral infection that is seen throughout the world. It has been recognized as a disease for more than 2000 years but was discovered to be a viral infection in the 1940s. As of 1999, it has been estimated that around 86 million people in the United States are infected. HSV-1 infections are the most common, with 50% to 80% infection rate of people in the United States. HSV-2 infections are equally as common with 1 in 5 Americans or 45 million infections. HSV-2 infections normally affect people in the age range of 14-49. Women are at a higher risk of infection for HSV-2 than males.  

Transmission

Transmission of the HSV virus is spread from skin to skin contact. It is a very fragile virus that can not live long on surfaces so it is not able to be contracted from objects such as counter surfaces and toilets. When skin contact occurs, the virus is able to infect someone through tiny tears in the skin or mucous membranes. Since most of the skin in too tough to penetrate, the virus normally affects the mouth and/or the genital area. This virus is normally found in the sores that appear in the mouth or genital areas. When the sores break open, the virus is released and can be spread. There are times when the virus does not produce sores but can still be transmitted. This is referred to as asymptomatic shedding.
HSV-1 can be spread from oral to oral contact, such as kissing, or oral-genital contact, such as oral sex. HSV-2 is almost always spread from sexual contact.

Signs and Symptoms

 Once the virus is transmitted, it can take several weeks for symptoms to occur. The first outbreak normally begins with blisters that burst and turn into sores. The sores can last anywhere from two to four weeks. In a small amount of cases, the blisters can be accompanied by flu-like symptoms including headache, fever, swollen glands, and painful urination. There are reported cases where the first outbreak can take months or sometimes years to occur making it impossible to know the origin of the virus. In most cases, the outbreak goes unrecognized as HSV because it is either not recognized or mistaken for insect bites or another skin condition.

After initial infection, the virus lays latent (def) in the nervous system. HSV-1 travels along the nerve pathways and lives in the dorsal root ganglion (def) of the trigeminal area (def). HSV-2 travels along the nerve pathways and lives in the dorsal root ganglion (def) of the sacral area (def). There are identified triggers that cause the virus to awaken in the body and travel from the nervous system to the skin. These triggers include emotional and physical stress, poor diet, illness, surgical trauma, overexposure to ultraviolet light, and steroidal medication. The virus can be managed with reduced stress, rest, good nutrition, and exercise.

Additional outbreaks can occur throughout the year though they are normally less severe and shorter. It had been documented that an infected person can expect 4-5 outbreaks per year.

The virus has a prodome (def) of painful, itching, or tingling feeling where the blisters are going to develop. Blisters can be expected to follow a day or two following this warning.

The virus can cause psychological distress and embarrassment to the infected person.

The virus can be more severe in immunocompromised (def) patients and can play a role in spreading HIV, the virus that causes AIDS.

It can present more severe and possibly fatal in neonates. It is most commonly spread to the baby when the mother has an outbreak during delivery. The neonate has an underdeveloped immune system that is unable to fight off the virus. The virus can lead to encephalitis (def) possibly causing brain damage.

Prevention and Treatment

The most effective prevention of HSV is to not have direct skin to skin contact with an infected person. Persons infected with HSV-2 are instructed to abstain from all sexual activity during prodome (def) or full-blown outbreaks. For people involved in a monogamous relationship, latex condom use has been shown to reduce the risk of transmission.

At this time, there is no known treatment or cure for HSV. There are several antiviral drugs on the market that help in episodic and suppressive treatments.

The oldest antiviral on the market is Acyclovir, known by its brand name Zovirax. It can be administered as a tablet, topical ointment, or intravenously. The antiviral inhibits DNA polymerase (def) resulting in faulty DNA replication.

Valacyclovir, known by its brand name Valtrex, is normally administered in tablet form. It is used for daily suppressive therapy to prevent recurring outbreaks. The antiviral inhibits DNA polymerase (def) resulting in faulty DNA replication.

Famciclovir, known by its brand name Famvir, is normally administered in tablet form. It is used for daily suppressive therapy to prevent recurring outbreaks. The antiviral inhibits DNA polymerase (def) resulting in faulty DNA replication.

There has been research into possible vaccines for HSV but as of today, nothing is in trial use.

Bibliography

American Social Health Association. Herpes Resource Center. Accessed on March 25, 2010 from http://www.ashastd.org/herpes/herpes_learn.cfm.

CDC. Center for Disease Control and Prevention, Division of STD Prevention. Genital Herpes. Accessed on March 25, 2010 from http://www.cdc.gov/std/Herpes/STDFact-Herpes.htm.

The Center for Food Security and Public Health. Infection Control. Disinfectant Resources. Virus Family Table. Accessed on March 25, 2010 from http://www.cfsph.iastate.edu/BRM/resources/Disinfectants/VirusFamilyTable.pdf.

Wikipedia. Herpes Simplex Virus. Accessed on March 25, 2010 from http://en.wikipedia.org/wiki/Herpes_simplex_virus