Chickenpox: Docile or deadly?
R Soman, S Madan
PD Hinduja National Hospital and Medical Research Centre, Mahim, Mumbai, Maharashtra, India
PD Hinduja National Hospital and Medical Research Centre, Mahim, Mumbai, Maharashtra
|How to cite this article:|
Soman R, Madan S. Chickenpox: Docile or deadly?.J Postgrad Med 2013;59:91-92
|How to cite this URL:|
Soman R, Madan S. Chickenpox: Docile or deadly?. J Postgrad Med [serial online] 2013 [cited 2020 Jun 4 ];59:91-92
Available from: http://www.jpgmonline.com/text.asp?2013/59/2/91/113808
Although smallpox has been eradicated, its "cousin" chickenpox remains an important cause of morbidity and, occasionally, mortality. The complications of chickenpox have been well described by Kole and colleagues in this issue of the journal. They make a strong plea for compulsory childhood varicella vaccination and vaccination of other risk groups. Varicella-zoster virus (VZV) infection causes two clinically distinct forms of disease, and humans are the only known reservoir.  Varicella or chickenpox, an extremely contagious infection, is the primary infection resulting from exposure of a person susceptible to the virus and is characterized by a generalized exanthematous rash. It is mainly a disease of childhood, but approximately 10% of individuals above 15 years of age are susceptible. Although the virus is endemic in the population at large, chickenpox exhibits seasonality during late winter and early spring. The other form, herpes zoster or shingles, results due to reactivation of the latent VZV virus in persons who are seropositive for VZV and is characterized by a more localized, dermatomally distributed eruption. It occurs at all ages, but mainly affects the elderly. Herpes zoster is a sporadic disease, and reactivation depends on a balance between the virus and host factors.
The mode of transmission of VZV is predominantly airborne; however, direct contact with the vesicular fluid can also transmit the virus. Incubation period of chickenpox ranges from 10 to 21 days, but it is usually 14-17 days. Patients are infectious 48 h before the onset of vesicular rash, during the period of vesicle formation which generally lasts for 4-5 days, until all the vesicles are crusted. Communicability may be prolonged in patients with altered immunity.
In the past, there was diagnostic confusion between chickenpox and smallpox due to similar appearance of the cutaneous lesions. However, with the eradication of smallpox, the differential diagnosis of chickenpox is less confusing, and the diagnosis is usually made by history and physical examination. The differential diagnosis mainly includes disseminated herpes simplex virus infection, disseminated coxsackievirus infection, echovirus infection, atypical measles, and rickettsial pox. Unequivocal confirmation of diagnosis is possible only through the isolation of VZV in susceptible tissue-culture cell lines, demonstration of either seroconversion or a four-fold or greater rise in antibody titer between acute and convalescent phase serum specimens or the detection of VZV DNA by polymerase chain reaction (PCR). A Tzanck smear, performed with the scraping of the base of the lesion, gives a rapid diagnosis by demonstration of multinucleate giant cells; however, the sensitivity is only 60%. 
The treatment of chickenpox includes symptomatic measures and antiviral therapy directed towards reduction of complications. Acyclovir (800 mg, five times a day for 7 days) is recommended for adolescents and adults. Acyclovir should not be used for the treatment routinely in otherwise healthy children; it is recommended for premature infants, secondary household cases, children with a history of chronic cutaneous or cardiopulmonary disorders, and those taking oral or inhaled steroids. Immunosuppressed patients should preferably be treated with intravenous acyclovir 10 mg/kg for 7 days. ,
For prevention of transmission of chickenpox in healthcare settings, the Centers for Disease Control and Prevention (CDC) recommends both airborne and contact isolation precautions.  In settings where airborne precautions cannot be implemented, masking the patient, placing the patient in a private room with exhaust fans and doors closed, and provision of at least masks for the healthcare personnel will reduce the likelihood of airborne transmission. Whenever possible, only immune healthcare workers (HCWs) should care for these patients. Post-exposure vaccination of the susceptible HCWs and other patients should be done as early as possible. For susceptible exposed persons for whom vaccine is contraindicated (immunocompromised persons, pregnant women, newborn whose mother had onset of varicella <5 days before delivery or within 48 h after delivery), varicella-zoster immunoglobulin (VZIG) should be administered within 96 h. If this is unavailable, intravenous immunoglobulin (IVIG) should be used. However, both are expensive. Oral acyclovir, initiated within 3-7 days after exposure and continued through the incubation period, is also effective in lessening disease severity. Airborne precautions are recommended for exposed susceptible persons. Leave from work is recommended for exposed susceptible HCWs, beginning 8 days after first exposure until 21 days after last exposure.
The Indian Academy of Pediatrics committee on Immunisation (IAPCOI) recommends offering the vaccine to all healthy children with no prior history of varicella, with special emphasis on high-risk groups. For primary immunization, the first dose should be given at the age of 15 months and the second dose at 4-6 years. For catch-up vaccination, children aged <13 years should receive 2 doses 3 months apart and those aged ≥13 years should receive 2 doses at an interval of 4-8 weeks.  The US Advisory Committee on Immunization Practices (ACIP) also recommends vaccination with two doses for all children aged ≥12 months, adolescents, and adults who do not have an evidence of immunity.  Seroconversion rates after one dose in children and adults are 95% and 78%, respectively. A second dose increases the seroconversion rate to 99%.  Post-exposure prophylaxis is reported to be 90% effective in preventing varicella if administered within 3-5 days after exposure. However, some reports have suggested that the real-life efficacy of vaccine may not be equivalent to that reported in initial studies, longer interval since vaccination may be associated with an increased risk of vaccine failure, and breakthrough infections in vaccinated persons can be as infectious as varicella in unvaccinated persons. 
There has been an argument regarding the effect of varicella vaccination on the epidemiology of zoster. Boosting of T-cell responses due to periodic environmental exposure may decrease the risk of developing zoster. However, this will decline with universal varicella immunization. The more effective the varicella vaccine is in reducing varicella, the more imperative is the need to administer an effective zoster vaccine that can mimic the community exposures to varicella.
Chickenpox during pregnancy needs a special mention because maternal infection can lead to congenital abnormalities with devastating consequences. If the mother acquires varicella infection during the early gestational period (weeks 8-20), the fetus is at risk of developing congenital varicella syndrome. This syndrome is associated with a mortality rate of 30% in the first few months of life and a 15% risk of developing herpes zoster in the first 4 years of life. Neonates born to mothers who have clinical disease within 5 days before delivery to 2 days after delivery are at the greatest risk for severe disease and poor outcome and should be administered VZIG. 
Chickenpox is an "ancient" disease. However, there are still some unanswered questions regarding it. Early treatment with acyclovir may reduce the severity of illness and transmission, but is early diagnosis possible? Will the push for early therapy result in unnecessary treatment of other similar eruptive illnesses? Will administration of acyclovir to a large number of patients lead to viral resistance? Is it worth the cost and effort for what is usually only a passing, benign, childhood illness? As humans are the only known reservoir for VZV, eradication of the disease may appear achievable with the availability of a fairly well-performing vaccine. However, the virus has a unique survival strategy in the subclinical and latent form, and it has an amazing method of ensuring that the next generation of humans is infected, either through varicella or through shingles!
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