Herpes Description of Infection Herpes refers to two types of viruses that may manifest as an infection of the reproductive system
Herpes
Description of Infection
Herpes refers to two types of viruses that may manifest as an infection of the reproductive system, otherwise, known as genital herpes (Tortora, Funke & Case, p. 762-764). In the United States, one in four people over age 30 has herpes, however, most of them are unaware they have the infection. The herpes virus is known more formally as the herpes simplex virus (HSV), and consists of two types – HSV type 1 is mainly responsible for cold sores, though it can contribute to genital herpes, while HSV type 2 is more directly attributed to genital herpes. HSV-1 in particular is much more common among young women and men who have sex with other men (CDC).
Symptoms tend to include lesions that appear on the genital area after an incubation period of up to a week (Tortora, Funke & Case, p. 762). These lesions cause a burning sensation, itching, and after a short period of time, vesicles with infectious fluid may appear and may make urination painful or even make walking and clothing uncomfortable. While the vesicles heal over time, there is always a chance of recurrence – approximately 90% for those with HSV-2 and about 50% for those with type 1 (Tortora, Funke & Case, p. 762). Men are more likely to experience recurrence than women, though reactivation is more usually attributed with immunocompromising factors like menstruation, emotional stress, or illness.
Although the vesicles contain infectious fluid, Tortora and colleagues write that the infection may often spread when symptoms are not apparent. Semen can contain the virus, while condoms may not offer adequate protection due to the position of vesicles on the genitals. About half the cases of HSV-1 infection stem from instances of genital-oral contact (Tortora, Funke & Case, p. 762). However, it is primarily transmitted through oral-oral contact, while HSV-2 is more or less exclusively transmitted through sexual intercourse (WHO). To be more specific, the virus enters through mucous membranes found in the various sites of infection (Lee).
Microbiology
HSV belongs to a group of pathogens known as the alpha herpesvirus group (Ayoade). It is an enveloped (polyhedral) virus, approximately 160 nm in diameter, with a linear, double-stranded DNA genome (Ayoade; Tortora, Funke & Case, p. 366). Sequence homology between the two types of the virus is moderate at about 50%, while HSV-1 has tropism for oral epithelium, and HSV-2 has tropism for genital epithelium (Ayoade). Infection is made possible by the attachment of ubiquitous receptors in the virus to cells, including even sensory neurons, which in turn leads to the establishment of latency (Ayoade).
As seen in the above image, the structure of the herpes virus is divided amongst 4 layers, with the DNA genome at the centermost layer. This is surrounded by the capsid, which in turn is surrounded by the tegument, itself encased within the envelope lined with glycoproteins.
Diagnosis
Visual examination of the herpes sores is the most common approach of diagnosis, though in some cases lab tests may also be conducted (Lee). A number of different lab tests can help confirm the diagnosis, and blood tests in particular may help identify the disease before it becomes symptomatic (Lee). The most common is a culture of the lesion with the virus, which can confirm diagnosis within 48 hours, as a cytopathic effect with ballooning of cells and cell death are observed, while immunofluorescence staining can distinguish between the two types (Ayoade). However, the sensitivity of a viral culture is fairly low, and drops dramatically as lesions begin to heal, also making it ineffective at diagnosing relapse (CDC). Tzank smears can also highlight the cytopathic process, but cannot distinguish between the two types, while polymerase chain reaction is more sensitive than cultures, but is normally reserved for more serious infections, like those involving encephalitis (Ayoade). In the majority of cases, viral culture and PCR are preferred, while PCR is the standard for infections that spread to the nervous system (CDC). Antibody testing can also demonstrate a primary seroconversion, particularly within HSV-1 in childhood, but is not effective for diagnosing relapse (Ayoade).
Treatment
There is no cure for herpes (CDC; Tortora, Funke & Case, p. 763). Discussions in this vein tend to revolve around ideas of management and suppression of the disease rather than curing it. Antiviral medications can help shorten the duration of outbreaks, and daily suppressive therapy can help minimize risks of transmission (CDC). Tortora, Funke & Case indicate that the primary pharmaceutical treatment is acyclovir (p. 763), however, famciclovir and valacyclovir may also be helpful in alleviating symptoms and improving the rate of healing (p. 763). Because of the potential of first-time presentations of HSV to affect the neurological system, even mild initial clinical manifestations are treated with antiviral therapy (CDC).
Prevention
Because herpes has no cure, a significant emphasis is placed on prevention. Epocrates lists prevention in two different categories. The first type is primary prevention, while the second is secondary. Primary prevention mainly consists of avoidance of sexual activity or contact, particularly when in the midst of an outbreak. Although condoms may not be fully effective all of the time, condoms may reduce risk of HSV-2 infection by as much as 96%, compared to no use of condoms (Epocrates). However, it is again important to note that condoms do not necessarily cover all of the areas of skin that may have the infection, which is why they are not commonly viewed as particularly protective against HSV. Somewhat paradoxically, circumcision in males has been attributed to a 25% reduction in HSV-2 infection in randomized trials; however this did not seem to affect the rate of transmission of HSV-2 to female partners (Epocrates).
Secondary prevention mainly consists of utilizing antiviral medications, as previously described, in order to reduce risk of transmission. Such therapy has been attributed with a 48% reduction of infection risk in heterosexual, monogamous relationships (Epocrates). To achieve maximum preventative effects, however, treatment must be used at the first symptom of an outbreak, and it is still recommended that, during an outbreak, patients avoid all oral contact, including sharing of utensils.
