References:
- Global Infectious Diseases and Epidemiology Online Network: Infectious Diseases of the Philippines, 2013 eBook Edition, ISBN 978-1-61755-582-4, by Stephen Berger. Accessed here.
| Agent | VIRUS - DNA. Herpesviridae, Alphaherpesvirinae: Human Herpesvirus 3 (Varicella-zoster virus) |
| Reservoir | Human |
| Vector | None |
| Vehicle | Air Direct contact |
| Incubation Period | 2 to 3 weeks |
| Diagnostic Tests | Viral culture (vesicles) Serology Nucleic acid amplification |
| Typical Adult Therapy | Respiratory isolation. Severe/complicated cases: Acyclovir 10 to 12 mg/kg IV q8h X 7d Adolescent / young adult: 800 mg PO X 5 per day X 7 d. Alternatives: Valacyclovir 1 g PO TID; or Famciclovir 500 mg PO TID |
| Typical Pediatric Therapy | Respiratory isolation. Acyclovir (severe/complicated cases) 150 mg/sq m IV q8h X 7d |
| Vaccines | Varicella Varicella-Zoster immune globulin |
| Clinical Hints | Cough and fever followed by a pruritic papulovesicular rash after 1 to 2 days; pneumonia is often encountered; case fatality rate = 4.3 per 100,000 cases (7% in immune-suppressed patients). |
| Synonyms | Chickenpox, Lechina, Skoldkopper, Vannkopper, Varicela, Varizellen, Vattenkoppor, Waterpokken, Windpocken. |
Perinatal Infection
Newborn infants whose mothers had onset of varicella within 5 days before delivery or within the 48 hours after delivery are at risk for neonatal varicella.
- Neonatal varicella carries a case-fatality rate as high as 30%.
- Maternal infection during the first 20 weeks of pregnancy carries a risk (0.4% to 2.0%) of congenital varicella, characterized by low birth weight, hypoplasia of extremities, dermal scarring, focal muscular atrophy, encephalitis, cortical atrophy, chorioretinitis and microcephaly.
Acute Infection
The predominant features of varicella are fever, cough, malaise, lymphadenopathy and a generalized pruritic vesicular rash typically consisting of 250 to 500 lesions.
- The rash generally begins on the scalp and proceeds to the trunk and extremities, with most lesions on the trunk.
- Skin lesions are initially maculopapular, progressing to vesicles on an erythematous base.
- Atypical varicella, including lesions on palms and soles, may mimic monkeypox in endemic areas.
Complications
Complications include hepatitis, encephalitis (notably involving the cerebellum), myelitis, arthritis, secondary bacterial infections, Reye’s syndrome, disorders of the facial and other cranial nerves, meningitis, cerebral venous thrombosis, transverse myelitis, acute urinary retention, pancreatitis, appendicitis, pneumonia, empyema, acute respiratory distress syndrome (ARDS), spontaneous pneumothorax, myocarditis, atrioventricular block, hemorrhagic pericarditis, optic neuritis, uveitis, acute retinal necrosis, necrotizing scleritis, deep venous thrombosis or thromboembolism, purpura fulminans, idiopathic thrombocytopenic purpura and hemophagocytic lymphohistiocytosis.
- Pyomyositis, osteomyelitis, necrotizing fasciitis or Fournier’s gangrene may occasionally complicate varicella.
- Post varicella cerebral infarction has been described in young, previously healthy children within a few months of VZV infection and is characterized by middle cerebral artery territory infarction and proximal MCA disease. A similar condition has been reported in immunocompromised patients following herpes zoster involving the ophthalmic branch of the trigeminal nerve as well as in the context of primary varicella complicated by granulomatous angiitis. Extra-cranial vascular thrombosis of large or small vessels has also been reported.
- VZ virus infection may be associated with facial nerve palsy or Ramsay-Hunt syndrome (Bell palsy unilateral or bilateral, vesicular eruptions on the ears, ear pain, dizziness, preauricular swelling, tingling, tearing, loss of taste sensation, and nystagmus)
- Immunocompromised individuals, neonates, infants, adolescents and adults are at risk of severe illness and complications.
- VZ virus infection can be a presenting symptom of hyperparathyroidism and occurs twice as often in persons with hypercalcemia than age-matched controls.
- Use of nonsteroidal anti-inflammatory drugs during primary varicella, has been implicated as a risk factor for subsequent occurrence of streptococcal necrotizing fasciitis.