Viral Skin Infections (HANDOUT) PDF

HERPES SIMPLEX VIRUS Gingivostomatitis and pharyngitis: most common clinical manifestations of first- episode HSV-1 infections Recurrent herpes labialis: most common clinical manifestation of reactivation HSV-1 in...

HERPES SIMPLEX VIRUS Gingivostomatitis and pharyngitis: most common clinical manifestations of first- episode HSV-1 infections Recurrent herpes labialis: most common clinical manifestation of reactivation HSV-1 infection HSV-1 infections: more than 90% of adults have antibodies to HSV-1 by the fifth decade of life (infections are acquired more frequently and earlier in life than infections with HSV-2) HSV-2 infections: antibodies are not detected routinely until puberty; antibody prevalence rates correlate with past sexual activity Virus readily isolated from vesicle fluid Infection is treated with acyclovir (agent most frequently used for treatment of HSV infections) Clinical features: Vesicles Latency: after primary infection, virus particles enter sensory nerve endings in the lesion and and are transported to the dorsal root (trigeminal) ganglion where they initiate latent infection in the sensory neurons Primary infection can occur in: Eye Fingers — herpetic whitlow Other skin sites where there is rubbing or trauma (e.g., in rugby football or wrestlers) — herpes gladiatorum HSV reactivation febrile illnesses direct sunlight stress trauma menstruation immunocompromised VARICELLA-ZOSTER VIRUS (VZV) causes chickenpox (varicella) and zoster (shingles) humans: only known reservoir for VZV chickenpox: highly contagious, with an attack rate of at least 90% among susceptible (seronegative) individuals. medium-sized double stranded DNA virus morphologically indistinguishable from HSV only one serologic type characterized by crops of vesicles that develop into pustules and then scab during primary infection, VZV in mucocutaneous lesions enter sensory nerve endings and establishes latent infection in sensory neurons in dorsal root ganglia reactivation: causes zoster in a dermatome (usually thoracic and unilateral) Modes of transmission: By inhalation of droplets from respiratory secretions and saliva Direct contact from skin lesions Conditions that predispose to zoster Increasing age Immunocompromised due to leukemia, lymphoma, AIDS, solid organ transplant or other drug induced immunosuppression Trauma or tumors affecting the brain or spinal cord HUMAN HERPESVIRUS 6 (HHV 6)  present in the saliva of over 85% of adults causes roseola infantum or exanthem subitum was first isolated in 1986 infection occurs in most populations in the first 3 years of life virus replicates in T and B cells and in the oropharynx where it is shed into saliva virus persists in the body after initial infection PARVOVIRUS B19 (B19V) nonenveloped, icosahedral viruses with a linear single-strand DNA genome a type member of the genus Erythroparvovirus exclusively infects humans, and infection is endemic resistant to both heat and solvent-detergent inactivation replicates primarily in erythroid progenitors: primary receptor is blood group P antigen (globoside) transmission: predominantly via the respiratory route followed by the onset of rash and arthralgia by the age of 15 years: 50% of children have detectable IgG antibodies most infections are asymptomatic or are associated with only a mild nonspecific illness main manifestation of symptomatic infection: erythema infectiosum (fifth disease or slapped-cheek disease ) diagnosis: detection of B19 IgM antibodies NO effective antiviral drugs; symptomatic treatment only NO vaccines available for prevention PAPILLOMAVIRUS over 120 different types of papillomavirus can infect humans double stranded DNA viruses causes skin papillomas (warts) are highly adapted to human skin and mucosa at least 40 types (HPV 6,11,16,18 can infect the anogenital tract and other mucosal areas and are sexually transmitted transmitted by direct contact PAPILLOMAVIRUS infections are associated with cancer of the cervix, vulva, penis and rectum SMALLPOX (VARIOLA) was a major scourge of humankind for at least 3,000 years caused by a Poxvirus spread from person to person by contact with skin lesions and via the respiratory tract last case recorded in Somalia in 1977 Successful eradication program no subclinical infections so cases could be easily identified virus eliminated from the body on recovery — NO CARRIERS HUMANS are the only hosts — NO ANIMAL RESERVOIRS An effective vaccine was available MONKEYPOX a DNA virus with rodents as the primary viral reservoir — zoonotic infection characterized by a systemic illness and a vesicular rash similar to variola  lymphadenopathy is a prominent feature compared with the lesions of varicella zoster virus infections (chickenpox), monkeypox lesions tend to be more uniform (i.e., in the same stage of development), diffuse, and peripheral in distribution MOLLUSCUM CONTAGIOSUM most common human disease resulting from poxvirus infections Transmission: skin to skin contact and fomites close contact (including sexual intercourse) contact sports Autoinoculation Diagnosis: clinical presentation confirmed by histologic demonstration of cytoplasmic eosinophilic inclusions (molluscum bodies) MEASLES Special features: nearly all infected individuals become unwell and develop disease — NO asymptomatic or subclinical infection disease is so characteristic that clinical diagnosis can nearly always be made without need for laboratory help there is only 1 antigenic type after infection, there is complete resistance to reinfection which is lifelong — SECOND ATTACKS ARE ALMOST UNKNOWN is highly infectious — nearly all susceptible children contract the disease on exposure Clinical features: respiratory symptoms Kopliks spots which are tiny white spots surrounded by a reddish zone appearing on the lateral buccal mucosa rash RUBELLA Single stranded RNA virus only one serotype principal impact is on the fetus transmitted by droplet infection diagnosed serologically no treatment there is an available vaccine