Epidemiology

According to the U.S. Centers for Disease Control and Prevention, one out of five of the total adolescent and adult population in the United States is infected with HSV-2. The incidence is even higher for HSV-1, which infects approximately 80% of the U.S. population. HSV-1 most commonly infects the lips and leads to lesions referred to as “cold sores,” but it can also produce genital lesions. HSV-2 is most often associated with genital herpes, but this virus can infect the mouth during oral sex. The most common locations for herpes simplex lesions are the mouth and the genitals, but infections of the eyes, brain, fingers, face, and esophagus are also seen (Table 174.1).

Table 174.1 Herpes Simplex Infections

^* Allen D, Dunn L. Acyclovir or valacyclovir for Bell’s palsy (idiopathic facial paralysis). Cochrane Database Syst Rev 2004;4:CD001869 [update of Cochrane Database Syst Rev 2001;4:CD001869]; and Salinas R. Bell’s palsy. Clin Evid 2003;10:1504–7 [update in Clin Evid 2006;15:1745–50].

Presenting Signs and Symptoms

The first time a patient experiences a herpes simplex outbreak (primary infection), he or she often notes a prodrome of symptoms such as fever, muscle aches, headache, malaise, and swollen lymph nodes up to a week before the skin eruptions appear. The first sign of infection of the skin appears 2 to 12 days after initial exposure and begins as cutaneous edema. This edema is quickly followed by the development of small, grouped vesicles on an erythematous base. The lesions typically dry out and heal within 7 to 10 days, although they can last up to 3 weeks. The symptoms almost always recur and are often heralded by a prodrome of skin itching, pain, or paresthesias at the site of infection. Recurrent outbreaks often occur at the same site as the primary infection, but they tend to be milder and have a shorter duration. These recurrences can erupt in intervals of days, weeks, or years, and the triggers vary by patient.

Diagnostic Testing

Herpes simplex is typically identified clinically by the characteristic skin lesion of a thin-walled blister on an inflamed base. Definitive testing is available, and the Tzanck smear uses scrapings from lesions to identify the giant cells with inclusion bodies indicative of HSV infection. Although this test is the most readily available, it is not very sensitive. Viral cultures can be accurate if material is collected early in the illness when intact vesicles are sampled, but the sensitivity wanes with the duration of symptoms. Polymerase chain reaction testing is available and is considered the “gold standard.” It is the fastest and most accurate for testing cerebrospinal fluid (CSF). Serum immunologic studies can be used to identify specific strains of the virus, but most of these tests are time consuming and expensive. Although one point-of-care test is available for HSV-2, it is not widely used, and treatment in the emergency department is most often based on clinical suspicion.

Treatment and Disposition

As yet, no cure for herpes simplex exists. Some of the most exciting research is in the area of vaccination. Several vaccines in clinical trials have the potential to eliminate infection.² Until then, herpes symptoms are managed using several different antiviral medications that help to reduce outbreaks and shorten the course of illness (see the “Facts and Formulas” box). The most commonly used agents are nucleosides and nucleotide analogues that block viral reproduction. They include acyclovir, valacyclovir, famciclovir, and penciclovir. Patients with a first episode of genital herpes, even with mild symptoms, should receive antiviral therapy to decrease progression to severe or prolonged symptoms.³ For acute outbreaks, valacyclovir and famciclovir are the most commonly prescribed medications, but they must be started within 1 day of lesion onset or during the prodrome that precedes some outbreaks.³ Once-daily valacyclovir can reduce the transmission rate of genital herpes by 50% to 75%.⁴ Low-dose suppressive therapy is also available for patients with frequent outbreaks. Foscarnet is a pyrophosphate analogue that can be used for treatment of HSV strains that have become resistant to the nucleosides and nucleotide analogues.

Epidemiology

VZV is the organism that causes varicella (chickenpox) and herpes zoster (shingles). Before the initiation of the varicella vaccination program, chickenpox was a very common illness, and 90% of cases occurred in children less than 10 years of age. Although most cases were uncomplicated, chickenpox led to 11,000 hospitalizations and 100 deaths every year before the introduction of the varicella vaccine. Adolescents and adults who contracted the illness tended to have a more prolonged and severe course. Since the introduction of widespread vaccination, the incidence of chickenpox has declined by 81%, thus leading to an 88% decline in varicella-related hospitalizations.⁵

Herpes zoster (shingles) occurs when the latent varicella virus is reactivated in the sensory ganglia. The lifetime incidence of herpes zoster is approximately 10% to 20% of the population, and most symptomatic infections occur in older or immunocompromised patients. In 2005, a safe, effective live attenuated vaccine was approved by the U.S. Food and Drug Administration and was recommended by the Advisory Committee on Immunization Practices after clinical trials demonstrated a significant reduction in morbidity secondary to herpes zoster and postherpetic neuralgia.⁶ An observational study reported a significant reduction in incidence of herpes zoster in patients 60 years old or older who received the vaccine regardless of age, race, or the presence of chronic diseases.⁷

Presenting Signs and Symptoms

A primary infection (chickenpox) is characterized by a diffuse, pruritic, vesicular rash 10 to 21 days after exposure. Patients with the illness typically experience a prodrome of 1 to 2 days of fever and malaise, followed by the eruption of macular lesions that progress to papules and then to vesicles that rupture and crust. Most often, the first lesions appear on the face or trunk and then spread to the extremities. Lesions may also involve the mucous membranes of the oropharynx, respiratory tract, vagina, cornea, and conjunctiva. The distinguishing feature of this rash is the presence of lesions in various stages in a single affected area. Patients less than 1 year old or more than 15 years old have the highest risk of complications, including skin infections, central nervous system involvement, and pneumonia. Chickenpox in pregnant women or neonates can lead to life-threatening pneumonitis, and primary infection during pregnancy may result in the congenital varicella syndrome.

As the patient recovers from a primary infection, the virus establishes a latent infection in the sensory dorsal root ganglia. Reactivation of this latent infection leads to the clinical symptoms of shingles. Patients frequently report a prodrome of fever, malaise, headache, and skin sensitivity before the eruption of the characteristic rash of grouped vesicles. The lesions typically crust by 7 to 10 days and resolve in 3 to 4 weeks. Pain is the most common symptom of shingles and is typically described as a burning sensation. The infection typically covers one dermatome, but it can occasionally affect neighboring dermatomes. Postherpetic neuralgia occurs in 10% to 15% of cases and is the most frequent complication of VZV. People who are more than 60 years old account for half of these cases. Postherpetic neuralgia is defined as the persistence of sensory symptoms more than 30 days after the onset of zoster. Herpes zoster ophthalmicus is a vision-threatening condition that requires ophthalmologic consultation. It is caused by involvement of the ophthalmic branch of cranial nerve V. The Hutchinson sign (a lesion on the tip of the nose) suggests the diagnosis, but it is not always present. Other complications include herpes zoster oticus (Ramsay Hunt syndrome) and disseminated herpes zoster, which can be identified by the rash crossing the midline or involving several dermatomes.

Chickenpox

Most cases of chickenpox follow a benign, uncomplicated course, and full recovery without chronic sequelae is expected. Treatment of varicella is aimed primarily at symptomatic relief. Acetaminophen is recommended for discomfort and fever. A small study from 1999 suggested a link between ibuprofen and necrotizing fasciitis in children with varicella.⁸ Although subsequent investigations have not been able to provide causal evidence, antiinflammatory medications continue to be associated with higher risk of invasive group A streptococcal infections, and these agents are not recommended in children with chickenpox.⁹ Another prominent symptom is severe pruritus, leading to excoriations and scarring. Oral antihistamines, calamine lotion, and oatmeal baths may be helpful.

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