THIRUVANANTHAPURAM:Chickenpox is a common viral infection caused by varicella-zoster virus. It is a highly contagious disease with secondary household attack rates of approximately 85% in susceptible individuals. Primary infection with this virus present as chickenpox (varicella) and an endogenous reactivation later causes a localized painful rash called herpes zoster (shingles).
Transmission of chickenpox is through inhaled respiratory droplets(eg: a cough, sneeze) of the affected person or by contact with skin lesions. It can also spread from skin rash of a person affected with shingles. The average incubation period that is, the time from exposure to onset of illness is 14-16 days(range:10-21days). The period of infectivity during which the affected person transmit the illness to others is around 48 hours prior to the onset of rash until all skin lesions get fully crusted.
Clinical features
Chickenpox comes with a prodrome of fever, malaise, sore throat, headache and loss of appetite, followed by skin rash within 24 hours. Rashes present as small itchy spots and bumps which later blister. Blisters are generally seen on a reddish base, classically described as 'dew drop on a rose petal appearance'. Rashes have a centripetal distribution with more lesions on trunk and less towards peripheries. The number of blisters that develop varies among individuals, although up to 250-500 lesions can occur. Lesions can also develop in the oral cavity.
New blister formation generally stops within 4 days and most lesions crust within 6-7 days. Crusts fall off within 1-2 weeks and may leave pigmented marks which take time to fade. This is generally a self-limited illness which usually results in lifelong immunity. Usually, no tests are required for diagnosis, unless complications occur.
Complications
Chance of complications, though rare, is more in adults than in children, pregnant women, newborn babies and immuno compromised individuals. These include bacterial superinfection, pneumonia, meningitis, encephalitis (inflammation of brain), hepatitis and ear infection. So, persistent cough, breathing difficulty, headache, fits, severe abdominal pain, earache or discharge requires immediate medical attention. Infection during early pregnancy may pose a risk of fetal anomalies.
Treatment
Treatments are basically measures to control fever or body ache with acetaminophen and itching with calamine lotion or antihistamines. Antiviral medications like acyclovir or valacyclovir help to reduce the number of skin lesions formed and to get better faster, if started early itself.
Taking adequate rest, wearing loose clothes to avoid skin irritation and drinking plenty of oral fluids to avoid dehydration is advisable. Maintaining adequate hygiene by bathing and avoiding scratching of skin lesions help to prevent secondary bacterial infection and scarring.
Isolation of affected individuals is essential to prevent spread of disease.
Prevention
Two doses of varicella vaccine are 88-98% effective at preventing varicella. Rarely, vaccinated people may get a breakthrough infection which is usually mild with fewer rashes and lesser risk of complications. In children, adolescents and adults,2 doses of vaccine are recommended with a minimum interval of 4 weeks. In children, 2 doses, first at 15-18 months of age and second at 4-6 years along with MMR vaccine as MMRV or separately are recommended.
Post-exposure prophylaxis after chickenpox may still be possible with vaccine if given within 3 to 5 days of exposure. Post -exposure varicella zoster immunoglobulin is indicated in immunocompromised individuals, malignancy, neonates and pregnant women. Hence, it is advisable for the exposed or affected individuals, especially the high-risk group mentioned above, to get early medical attention, either for disease prevention or to avoid the risk of complications.
Dr Mini P N,Consultant Dermatologist,KIMS, Thiruvananthapuram
(The views expressed by the author are her own)