Herpes Simplex Flashcards
Briefly describe the herpes simplex virus
The major clinical manifestations of infection with herpes simplex virus (HSV) type 1 (HSV-1) or HSV type 2 (HSV-2) are oral, genital and ocular ulcers.
Less commonly, primary or recurrent HSV infections may also present at other sites with neurological, hepatic, or respiratory complications.
The primary episode occurs during initial infection with HSV, in which the host lacks an antibody response.
Briefly differentiate between HSV-1 and HSV-2
HSV-1 is most associated with cold sores. It is often contracted initially in childhood (before five years), remains dormant in the trigeminal nerve ganglion and reactivates as cold sores, particularly in times of stress. Genital herpes caused by HSV-1 is usually contracted through oro-genital sex, where the virus spreads from a person with an oral infection to the person that develops a genital infection.
HSV-2 typically causes genital herpes and is mostly a sexually transmitted infection. It can also cause lesions in the mouth.
Briefly describe the transmission of herpes simplex
The herpes simplex virus is spread through direct contact with affected mucous membranes or viral shedding in mucous secretions. The virus can be shed even when no symptoms are present, meaning it can be contracted from asymptomatic individuals. Asymptomatic shedding is more common in the first 12 months of infection and where recurrent symptoms are present.
Briefly describe the structure of HSV-1 and HSV-2
HSV-1 and HSV-2 are large, enveloped, double-stranded DNA viruses.
Briefly describe the latent period of herpes simplex
After an initial infection, the virus becomes latent in the associated sensory nerve ganglia. Typically this is the trigeminal nerve ganglion with cold sores and the sacral nerve ganglia with genital herpes.
What are the risk factors for herpes simplex infection?
- Rsik factors for clinical disease:
- HIV infection
- Immunosuppressive medications
- Risk factors for seropositivity:
- High-risk sexual behaviours
- Female
- Black
- Increasing age
- Lack of condom use
What are the clinical features of herpes simplex?
- Dysuria (in women)
- Lymphadenopathy
- Genital ulcer
- Oral ulcer
- Tingling sensation
Briefly describe how genital ulcers present
Multiple, painful ulcers start as vesicular lesions and progress to ulceration, then crusted lesions.
Briefly describe how oral ulcers present
Typically single, recurrent, painful, self-limited ulcer along the vermilion border.
Briefly describe the diagnosis and investigations of genital herpes
Genital herpes is caused by infection with either HSV type 1 (HSV-1) or HSV-2. If lesions are present, clinical diagnosis should be confirmed by swabbing lesions for HSV culture or HSV polymerase chain reaction (PCR).
Glycoprotein G-based type-specific serology (gG1 and gG2 for HSV-1 and HSV-2, respectively) can be useful to assess the risk in asymptomatic pregnant women for potential transmission to the infant at the time of delivery, to assess risk in a sexual partner of a patient with documented genital infection, or to confirm diagnosis in patients with atypical complaints or previously undiagnosed genital ulcer disease.
Briefly describe the diagnosis and investigations of herpes labialis
The diagnosis can be made clinically, but HSV culture or PCR should be performed on active lesions if there is a question about the diagnosis.
Briefly describe the approach to treating herpes simplex
The principles of therapy for oral and genital herpes are similar. Therapy is divided into two groups: suppressive and episodic.
Suppressive antiviral therapy is taken daily to prevent recurrences and shedding, and episodic therapy is used as needed to treat recurrences.
Episodic treatment should be started immediately after clinical diagnosis of active disease, especially during the first clinical episode. If there is a suspicion for first-episode genital herpes, treatment should be started prior to laboratory confirmation.
Briefly describe the role of oral antivirals in treating herpes simplex
Oral antivirals are the primary treatment. They are indicated for both suppressive and episodic therapy. The goal of daily suppressive treatment is to decrease the number of outbreaks (70% to 80% reduction) and/or reduce the risk of genital herpes transmission (48% reduction). The goal of episodic treatment is to shorten the duration of the outbreak.
The synthetic acyclic purine analogues (or guanine analogues) are highly specific substrates for the viral thymidine kinase and inhibit viral DNA polymerase. All three licensed drugs (aciclovir, famciclovir, and valaciclovir) are effective at shortening the duration and severity of an episode.
What is suppressive therapy? When is it used?
Daily suppressive therapy may be offered for persons wishing to prevent recurrences, and may be considered for HIV-uninfected patients with genital herpes who wish to decrease the risk of transmission to sexual partners. The need for suppressive therapy should be re-evaluated on a yearly basis.
Briefly describe the mechanism of action of oral antivirals treating herpes simplex
The synthetic acyclic purine analogues (or guanine analogues) are highly specific substrates for the viral thymidine kinase and inhibit viral DNA polymerase. All three licensed drugs (aciclovir, famciclovir, and valaciclovir) are effective at shortening the duration and severity of an episode.
