Varicella
FAQs for Health Care Providers
Varicella (Chickenpox) Risk, Diagnosis, and Treatment in Afghan Evacuees
Varicella is a highly contagious infection due to the varicella-zoster herpesvirus (VZV) that causes a rapidly progressive, generalized, pruritic rash evolving from maculopapular to characteristic vesicular lesions that eventually crust over. It may cause serious complications, including death, especially in adults. After primary infection the VZV becomes latent in the sensory nerve ganglia and may reactivate causing herpes zoster (shingles).
Have there been confirmed cases in the Afghan evacuees? Yes, there have been multiple cases (outbreak)
Epidemiology
Varicella infection occurs throughout the world. Humans are the only known reservoir. It is predominantly a childhood disease in temperate climate areas, with the highest incidence in March through May. In contrast, varicella infection tends to occur in later childhood through young adulthood in countries with more tropical climates. The incidence of varicella in high-income countries is 15-16/1000 per year and has decreased with higher vaccination rates. Unfortunately, data from low- and middle-income countries is limited. A vaccine campaign is being conducted due to an ongoing varicella and measles outbreak in Afghan newcomers.
When should I consider Varicella?
Clinical Presentation
The incubation period is 14-16 days (range 10-21 days). A mild prodrome of fever, malaise and sometimes pharyngitis can precede the initial development of the rash, especially in adults by 1-2 days. Usually, the rash is generalized but first appears on the trunk with subsequent spread to the extremities, it is pruritic and begins with a maculopapular appearance which evolves forming vesicular lesions. The varicella vesicles are frequently described as a “dew drop on a rose petal” and are at various stages of development.
The differential diagnosis (Table 1) for maculopapular rash includes many infections, including Roseola, Parvovirus, staph-related infections, and more. Vesicular rash differential includes measles and HSV. Measles usually starts on the head and neck and spread downwards. Smallpox is considered eradicated but is still stored as a bioweapon and typically developed on extremities and moved towards the trunk.
Common complications include secondary bacterial skin infections (particularly in children) and pneumonia (particularly in adults). Adults, premature infants, pregnant women and immunocompromised individuals are at higher risk of complicated VZV infections. Other severe complications include CNS manifestations such as aseptic meningitis or encephalitis, cerebellar ataxia, disseminated disease with multiorgan involvement, hemorrhagic manifestations and others.
See more photos here.
Is varicella contagious?
Yes, extremely contagious. On average, each case of varicella transmits the infection to an estimated 12-18 other people. Incubation period is from 10-21 days. The infectious period starts 48 hours before the development of a rash and lasts until there are no new lesions for 24 hours and all lesions have crusted over.
Of note, varicella breakthrough infections can rarely occur after varicella vaccination and are infectious. Breakthrough VZV can occur in vaccinated individuals and is defined as occurring >42 days after completing the vaccine series. Breakthrough infection is usually milder with <50 lesions. Herpes zoster (Shingles) is a secondary manifestation of the varicella zoster virus and is also infectious.
Are there special infectious disease precautions for someone with varicella?
Airborne and contact precautions are required for when varicella infection is suspected. Transmission can happen via droplets, aerosols, or direct contact with infected individuals.
Healthcare workers caring for Afghan refugees should have demonstrated immunity through vaccination, documented diagnosis of historical varicella infection, or laboratory evidence of adequate protective titers. This is particularly important for pregnant women in whom vaccination is contraindicated.
Given the approximately two-week incubation period of varicella, CDC guidelines have typically recommended quarantine from day 8 to day 21 after known exposure.
New arrivals and those working with new arrivals should be assessed for immunity and offered vaccination if immune status is unknown or they are determined to be non-immune.
How do I diagnose Varicella?
Varicella is usually a clinical diagnosis based on the classic characteristic vesicular rash. PCR testing is available for laboratory confirmation, which may be helpful especially in cases where there are atypical clinical features. Ideal specimen for PCR testing is obtained by unroofing a fresh vesicle and swabbing the base. Direct fluorescent antibody testing, and viral culture are less sensitive alternative methods of confirmation.
What is the treatment for Varicella?
Treatment with antiviral agents is indicated depending on individual patient risk factors for complications and should be started early, ideally within 24 hours of onset of rash.
Antivirals are indicated for:
High risk individuals:
Individuals older than 12 years old
Pregnant women
Premature neonates and infants
Chronic skin or lung disease
Immunocompromised patients
Severe cases
Individuals using ongoing salicylate or inhaled corticosteroids
For immunocompetent individuals, oral acyclovir or valacyclovir can be used for treatment:
For less severe cases:
Patients less than or equal to 40 kg: Acyclovir 20 mg/kg orally 4 times daily for 5 days
Patients greater than 40 kg: Acyclovir 800 mg orally 4 times daily for 5 days
For more severe cases:
Acyclovir 10 mg/kg/dose IV every 8 hours for 7-10 days or no new lesions have developed for 48 hours
Note: Valacyclovir is sometimes used as an alternative antiviral medication. See uptodate.com or AAP Redbook for more information.
Note:
Aspirin is generally contraindicated in pediatric populations and there have been cases of Reye syndrome in children with Varicella infections.
Acyclovir is a class B drug during pregnancy according to the FDA.
Postexposure prophylaxis
In cases of exposure of some high risk individuals, vaccination can be used for postexposure prophylaxis and has been found to prevent infection in susceptible individuals at rates of 70-90%. Per the CDC, individuals who have been exposed to varicella and cannot receive the varicella vaccine, varicella immune globulin may be indicated for those 1) who lack evidence of immunity to varicella, 2) whose exposure is likely to result in infection, and 3) are at high risk for severe varicella. See managing people at high risk for severe varicella.
Contributors
Rosemary Liu, MD
Emily Halverson, MD
Risha Moskalewicz, MD
Cindy Howard, MD
William Stauffer, MD
Varicella_FAQ_Oct_11.pdf