VIRAL

• Viral exanthems


  Skin manifestations of viral infections
• A number of viruses and bacteria produce infections that have skin manifestations. These skin manifestations may be a part of the disease and are referred to as exanthems. The most common causes are viruses.
• Macule


  An alteration in skin color that cannot be palpated
• Papule


  A palpable solid lesion smaller than 0.5–1.0 cm
• Nodule


  A palpable lesion larger than a papule
• Vesicle


  A raised, fluid filled lesion less than 0.5 cm in diameter
• Bulla


  A larger form of vesicle
• Pustule


  Similar to a vesicle but contains purulent material instead
• Measles (Rubeola)


  A common and highly contagious childhood exanthem associated with serious complications
• Rubella (German Measles)


  One of the common viral exanthems in childhood, a benign infection in children but more severe in adults, especially during pregnancy

  
• Roseola Infantum (Exanthem Subitum or Sixth Disease)

  Caused by Human Herpes Virus 6 (HHV6), primary infection in young children
• Erythema Infectiosum (Fifth Disease)

  Caused by Parvovirus B19, a single stranded DNA virus that targets erythroid progenitor cells
• Fifth disease


  Associated with viremia and can cross the placenta and infect the fetus
• Mode of Transmission of Fifth disease

  1. Transmitted by respiratory droplets and oral secretions

  2. Can also be transmitted by blood transfusions and vertical transmission from an infected mother
• Fifth disease


  • Common in early school age children and less common in adults
  • Biphasic infection consisting of the lytic stage and the immunologic stage
  • Initial lytic stage is most contagious
  • Followed by immunologic stage characterized by a generalized lace like rash most prominent over the face ("slapped cheek" appearance) and arthralgia
  • In adults leads to polyarthritis involving the wrists, knees, and ankles
  • Most serious complication is aplastic crisis in patients with chronic hemolytic anemia
  • In pregnant women, associated with high risk of fetal death due to congestive heart failure (hydrops fetalis)

  
• Diagnosis of Fifth disease


  • Based on clinical presentation
  • Can also be diagnosed through ELISA and polymerase chain reaction (PCR)
• Treatment and Prevention of Fifth disease


  No specific antiviral treatment or vaccine available
• Varicella (Chickenpox)


  • Benign, self-limiting, and highly communicable infection in children but associated with severe infections in adults
  • Caused by Varicella Zoster Virus (VZV), a double stranded, enveloped DNA virus that belongs to the Herpesvirus family
  • Infects mucoepithelial cells and establishes latency in nerve ganglia
  • Virus persists in the infected host for an indefinite period and produces recurrent infections (zoster or shingles) especially in elderly and immunocompromised persons

  
• Mode of Transmission of Varicella

  1. Most commonly transmitted by inhalation of respiratory droplets

  2. May also be transmitted by direct contact with the lesions
• Clinical Findings of Varicella

  • Characterized by fever and vesicular eruptions on the skin and mucous membranes
  • Rashes are initially maculopapular which later become vesicular with associated intense pruritus
  • Vesicles rupture and ulcerate and later leads to scab formation (crusts)
  • Lesions appear in crops of different stages and all the stages of the lesions (macule, papules, vesicles, ulcers, crust) appear simultaneously
  • Vesicles are described as "teardrop on a pink base" or "dew drop on a rose petal"
  • Lesions are superficial and do not leave permanent scars
  • Complications include pneumonia (in adults) and encephalitis (in children)

  
• Laboratory Diagnosis of Varicella

  Based on clinical manifestations and a Tzanck smear of skin scrapings or swab from the vesicle to demonstrate the Cowdry type A inclusions and multinucleated giant cells

  
• Treatment and Prevention of Varicella

  • Treatment is mainly symptomatic
  • Acyclovir has been shown to be effective in reducing the course of the disease but does not prevent latency and recurrent infections
  • Prevention is by administration of Varicella Zoster Virus vaccine, a live attenuated vaccine
• Herpes Zoster (Shingles)


  • Caused by the reactivation of a latent chickenpox infection
  • First manifestation is severe radicular pain over the skin supplied by sensory ganglia
  • Most commonly involved dermatome is the thoracic dermatome
  • May also involve other cranial nerves like the trigeminal, facial, or auditory nerves
  • Rashes are similar in appearance to that of chickenpox but differ in two aspects: (1) limited distribution to the skin innervated by a single sensory ganglion, and (2) the rashes are painful rather than pruritic
  • Most common complication is post herpetic neuralgia, a form of prolonged pain that may persist for months

  
• Variola (Smallpox)


  • Contagious infection responsible for very high fatality rate worldwide before the 18th century
  • Controlled through the process known as variolation, which involved inoculation of high risk individuals with live virulent virus
  • Edward Jenner developed a live vaccine from cowpox in the 17th century
  • Last reported case was in Somalia in 1977, declared totally eradicated through vaccination in 1980
  • Success of vaccination attributed to: (1) only one stable serotype, (2) no animal reservoir and humans are the only hosts, (3) no subclinical state, and (4) easily clinically recognizable
  • Listed among the Category A bioterrorism biowarfare agents by the Center for Disease Control and Prevention of the United States

  
• Etiologic Agent of Variola


  • Variola virus, a member of the human Poxviruses, the largest among the DNA viruses
  • Shares antigenic determinants with animal poxviruses, so Cowpox virus has been successfully used in the development of vaccines for smallpox
• Mode of Transmission of Variola

  1. Primary mode is through inhalation

  2. Can also be transmitted by direct contact with the lesions, dried virus, or contaminated materials like clothing
• Clinical Findings of Variola

  • Two variants: smallpox minor (1% mortality) and smallpox major (up to 40% mortality)
  • Presents with fever and malaise, followed by the appearance of rashes that are macular that then become papular, later becoming vesicular, and eventually pustular
  • Lesions appear one stage at a time, unlike chickenpox
  • Lesions are deep seated, leaving permanent scars
  • In severe cases, the rashes may become hemorrhagic

  
• Laboratory Diagnosis of Variola

  • Disease is easy to recognize based on the symptoms
  • Virus isolation can be done by growing of the virus in chorioallantoic membrane of embryonated eggs where the characteristic pocks develop
  • Antibody assays can confirm the diagnosis

  
• Treatment and Prevention of Variola

  • Methisazone is effective as prophylaxis but not for therapeutic purposes
  • The vaccine is a live, attenuated vaccine
  • Smallpox has been totally eradicated since 1980 because of the success of vaccination
• The five most common childhood exanthems are measles, chickenpox, German measles, roseola, and fifth disease
• All five exanthems are caused by viruses, worldwide in distribution, and highly contagious
• Measles, Rubella, and chickenpox are preventable by vaccination

  
• Rubeola or measles is characterized by fever, a prodrome consisting of the 3 C's (coryza, cough, conjunctivitis with photophobia), Koplik's spots, and maculopapular rash with desquamation
• Rubella is a common cause of congenital viral infection

  
• Roseola is the most common cause of febrile seizures in children
• Herpes zoster or shingles present with severe pain over the path of sensory nerve distribution followed by appearance of vesicular lesions
• Fifth disease generalized erythematous rash but it is most prominent over the face and is described as "slapped cheek" appearance

  
• Smallpox is a highly contagious viral infection
• Smallpox was totally eradicated in 1980 by vaccination