Viral disease update

Abstract

Eight human herpesviruses have been identified and 10 antiviral drugs are Food and Drug Administration approved for their therapy. The herpesviruses are unique in that they all may cause primary infection, establish latency, and then reactivate if conditions of altered immunity develop. Herpes simplex virus type 1 is usually the cause of herpes labialis or cold sores. More than 85% of the population is seropositive for this virus, although only 20% to 40% of people have recurrent orolabial outbreaks. Herpes simplex virus type 2 (HSV-2) is the most common cause of genital herpes infection. One of every 5 people more than 12 years old is seropositive for HSV-2. The incidence has increased by 30% since 1976. Most people do not even know that they have been infected with the virus and that they can transmit the virus to a sexual partner. The antivirals acyclovir, valacyclovir, and famciclovir modify recurrent outbreaks of genital herpes and suppress outbreaks when taken on a daily basis. The side effects are comparable to those of placebo and no drug interactions have been identified. Valacyclovir may even prevent the transmission of HSV-2 from a seropositive person to a seronegative partner. Vaccines to modify recurrences of herpes simplex infections and prevent infections show promise. Varicella zoster virus causes varicella (chickenpox) and zoster (shingles). A live attenuated vaccine is available to prevent varicella. Acyclovir, valacyclovir, and famciclovir modify the very painful reactivation of varicella zoster virus in shingles. Famciclovir even decreases the length and severity of postherpetic neuralgia that can be debilitating in the elderly. Epstein-Barr virus, the fourth human herpesvirus, is associated with infectious mononucleosis and lymphoproliferative diseases in immunocompromised patients. Cytomegalovirus, the fifth human herpesvirus, is typically symptomatic only in neonates and the immunocompromised. Human herpesvirus type 6 causes a mild, self-limited disease in childhood called sixth disease or exanthem subitum. No diseases have definitively been linked to the seventh human herpesvirus, but it is speculated that pityriasis rosea may be linked to this virus. The eighth human herpesvirus is associated with the violaceous lesions of Kaposi's sarcoma. The poxvirus manifests as molluscum contagiosum in children and sexually active adults and is most troublesome in the immunocompromised. Treatment with the antiviral cidofovir results in remarkable clearance of molluscum contagiosum in human immunodefiency virus-infected individuals. Human papillomaviruses cause warts anywhere on the body. An estimated 30% to 50% of the sexually active population has genital human papillomavirus infection, called condyloma acuminata. Several types of human papillomavirus are associated with anogenital cancers. Human papillomavirus DNA is found in greater then 93% of cervical cancers, the second most common cause of cancer death in women throughout the world. Earlier treatments of these infections involved nonspecific tissue destruction and significant recurrence rates. Podofilox gel and solution are safe and effective for self-treatment of genital warts. Treatment with imiquimod, an immune-response modifying agent that induces interferon alfa and other cytokines, results in clearance of warts and human papillomavirus DNA. There are no systemic side effects and local inflammatory reactions are tolerable for most patients. The viral exanthems, measles and rubella, have made a resurgence in recent years. Most cases in the United States have been linked to international importations. Hepatitis C is a parenterally transmitted RNA virus. Chronic hepatic disease occurs in 50% of patients with acute hepatitis C infection. Chronic disease can lead to cirrhosis and hepatocellular carcinoma. Dermatologic manifestations may be the only clinical evidence of underlying disease. Findings may include pruritus, porphyria cutania tarda, vasculitis, salivary gland lesions, lichen planus, polyarteritis nodosa, urticaria, erythema nodosum, and erythema multiforme. A new combination therapy of ribavirin capsules and interferon alfa-2b recombinant for injection results in 45% of patients able to sustain reduced hepatitis C virus levels.