Also known as: Chickenpox, VZV-varicella zoster virus
Hospital: Report outbreaks
Infection Preventionist: Report outbreaks
Physician: Report outbreaks
Follow-up of investigation by Local Public Health Agency (LPHA): outbreaks only
Iowa Department of Public Health
Disease Reporting Hotline: 1-800-362-2736
Varicella-Zoster is a member of the herpesvirus family.
B. Clinical Description
Symptoms: Primary infection results in varicella (chickenpox). A mild prodrome may precede the onset of a rash. Adults may have 1 to 2 days of mild fever and malaise. Prior to rash onset, but in children the rash is often the first sign of disease.
The rash is generalized, pruritic, and rapidly progresses from macules to papules to vesicular lesions before crusting. The rash typically consists of 250 to 500 lesions; appear first on the scalp, moves to the trunk, and then the extremities, with the highest concentration of lesions on the trunk (centripetal distribution). The vesicles are superficial and delicate; contain clear fluid on an erythematous base. Usually 2 to 4 successive crops of lesions, crops appear over several days, with lesions present in several stages of development. The rash is self-limited, generally lasting 4-5 days.
The clinical course in normal children is generally mild, with malaise, pruritus, and fever up to 102o F for 2-3 days. Adults may have more severe disease and have a higher incidence of complications. Respiratory and gastrointestinal symptoms are absent.
Complications: The risk of complications from varicella varies with age. Children with lesions due to varicella are at greater risk for secondary bacterial infections. Complications are infrequent among healthy children. They are much higher in persons > 15 years and infants < 1 year of age. Adults account for only 5% of reported cases of varicella, but account for approximately 35% of mortality.
Complications include bacterial superinfection of the skin lesions, pneumonia (viral or bacterial), thrombocytopenia, arthritis, hepatitis, cerebellar ataxia, encephalitis, meningitis, and glomerulonephritis. Reye Syndrome can follow some cases of chickenpox, although the incidence of Reye Syndrome has decreased dramatically with decreased use of salicylates during varicella or influenza-like illnesses. Severe and even fatal varicella has been reported in otherwise healthy children receiving intermittent courses of corticosteroids for treatment of asthma and other illnesses.
The hospitalization rate is 3 per 1000 cases. Death rate 1 per 60,000 cases.
Outcome: Recovery from primary varicella infection usually results in lifetime immunity. In otherwise healthy persons, a second occurrence of chickenpox is uncommon, but may occur, particularly in immunocompromised persons.
The virus establishes latency in the dorsal root ganglia during primary infection. Reactivation results in herpes zoster “shingles”. Grouped vesicular lesions appear in the distribution of 1 to 3 sensory dermatomes, sometimes accompanied by pain localized to the area. The immunologic mechanism that controls latency of VZV is not well understood. Approximately 15-30% of the population will experience zoster during their lifetimes. Factors associated with recurrent disease include aging, immunosuppression, intrauterine exposure to VZV, and varicella at a young age < 18 months. Post herpetic neuralgia is defined as pain that persists after resolution of the rash, may last as long as a year after the episode of zoster.
Herpes Zoster Vaccine
Zoster vaccine (licensed in 2006 Zostavax) is a live attenuated vaccine approved for persons 60 years of age and older. ACIP (Advisory Committee on Immunization Practices) recommends a single dose of zoster vaccine for adults 60 years of age or older whether or not they report a prior episode of herpes zoster. Persons with a chronic medical condition may be vaccinated unless a contraindication or precaution exists for the condition.
For more information on zoster vaccine, visit: www.cdc.gov/vaccines/vpd-vac/shingles/default.htm#clinical
The vaccine should be stored frozen at an average temperature of +5°F (-15°C) until it is reconstituted. Read and follow the package insert for storage and reconstitution instructions.
A person should not get shingles vaccine who:
- has ever had a life-threatening allergic
- reaction to gelatin,
- the antibiotic neomycin,
- or any other component of shingles vaccine.
- has a weakened immune system because of
- HIV/AIDS or another disease that affects the immune system,
- treatment with drugs that affect the immune system, such as steroids,
- cancer treatment such as radiation or chemotherapy,
- a history of cancer affecting the bone marrow or lymphatic system, such as leukemia or lymphoma.
- has active, untreated tuberculosis.
Humans are the only source of infection for this highly contagious virus.
D. Modes of Transmission
Spread: The varicella zoster virus enters the body through the respiratory tract and conjunctiva. The virus is believed to replicate at the site of entry in the nasopharynx and regional lymph nodes. Primary viremia occurs 4-6 days after infection, which disseminates the virus to other organs, such as the liver, spleen and sensory ganglia. A secondary viremia occurs with viral infection of the skin.
Person-to-person transmission occurs by airborne spread from respiratory tract secretions and by direct contact with drainage from lesions in patients with varicella. Patients with zoster spread disease primarily by direct contact with drainage from zoster lesions. Transmission may also occur by respiratory contact with airborne droplets or by direct contact or inhalation of aerosols from vesicular fluid of skin lesions of acute varicella or zoster. Patients with disseminated zoster may also transmit disease via the airborne route. In utero infection also can occur as a result of transplacental passage of virus during maternal varicella infection.
E. Incubation period
The incubation period is from 14 to 16 days from exposure with a range of 10 to 21 days. Incubation may be prolonged in immunocompromised patients.
F. Period of Communicability or Infectious Period:
Patients are most contagious from 1 to 2 days before to shortly after onset of the rash. Contagiousness persists until crusting of the lesions.
Varicella is highly infectious, with secondary infection rates in susceptible household contacts approaching 90%. Secondary family cases may have more severe disease than that in the index case.
In temperate climates varicella is a childhood disease with a marked seasonal distribution with peak incidence during winter and early spring. In tropical climates, the epidemiology of varicella is different; acquisition of disease occurs at later ages, resulting in a higher proportion of adults being susceptible to varicella compared with adults in temperate climates.
In the prevaccine era (prior to 1995), most cases of varicella in the United States occurred in children younger than 10. With the implementation of universal immunization, a higher proportion of cases are expected to occur among adolescents and adults. As vaccine coverage increases and the incidence of wild-type varicella decreases, a higher proportion of varicella cases will occur in immunized people as break-through disease. In sites conducting active surveillance, cases of breakthrough disease have increased as a percentage of all cases from 4% in 1995 to 25% in 2000. This should not be confused as an increasing rate of breakthrough disease or as evidence of increasing vaccine failure.
H. Bioterrorist Potential:
None - differentiate from smallpox.
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Varicella can be found at: www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis.htm#top
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
Comment: Two probable cases that are epidemiologically linked are considered cases, even in the absence of laboratory confirmation.
Advisory Committee on Immunization Practices Prevention of Varicella: Recommendations of the Advisory Committee on Immunization Practices (ACIP) MMWR1999; 48(NO.RR-6).
American Academy of Pediatrics. Red Book 2006: Report of the Committee on Infectious Diseases, 27th Edition. Illinois, American Academy of Pediatrics, 2006.
CDC. Manual for the Surveillance of Vaccine-Preventable Diseases, CDC, 2002.
CDC Web-site Herpes Zoster - Vaccine Q&As for Providers (Shingles) www.cdc.gov/vaccines/vpd-vac/shingles/hcp-vaccination.htm
Epidemiology and Prevention of Vaccine Preventable Diseases. Ninth Edition January 2006.
Heymann, D.L., ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.