What is Chickenpox?
Chickenpox is an airborne and highly contagious infectious disease characterised by fever and a blister-like, itchy rash caused by the varicella-zoster virus (VZV). A person of any age can contract chickenpox and it is a potentially serious disease when it occurs in babies, adolescents, adults, women are pregnant, and people with compromised immune systems.
Transmission
Approximately 90% of close contacts, who are non-immune, will catch chickenpox after exposure to persons with the disease. A person with varicella is contagious from 1-2 days before rash onset until the sores have crusted. The incubation period is approximately 10-21 days after exposure to the virus and spreads through infected respiratory secretions, for instance coughing or sneezing.
Symptoms
Fever, lethargy, loss of appetite, headache and malaise (feeling ill) may occur 1 to 2 days before rash onset, particularly in adults. In children, the rash is often the first sign of disease and usually appears first on the head, chest, and back before spreading to the rest of the body. The rash is itchy and progresses rapidly from flat sores to fluid-filled blisters before crusting. Generally, lesions appear in crops, and are therefore present in different stages of development – some at the papule, others at the blister and still others at the crusted stage. Asymptomatic infection (without rash, or with very few blisters) may occur.
Diagnosis, treatment and prevention
Generally chickenpox is diagnosed clinically and typically requires no medical treatment – the disease has to run its course. Lotions, such as calamine lotion, can be applied to the skin to ease itching. Persons with severe infection may be treated with an antiviral medication.
Vaccination against varicella is not part of the Expanded Programme of Immunisation in South Africa, but is indicated for children and adults in high risk categories. The ideal age of vaccination is between 12-15 months. Individuals vaccinated against chickenpox can still get the disease, though they usually suffer from milder symptoms.
Diagnosis, treatment and prevention
Specialised laboratory diagnostic investigation for arboviral diseases is required to confirm or exclude diagnosis. Typically, the viraemic phase of arbovirus infections are so short (may be prolonged in more severe cases) and negative RT-PCR results does not exclude the diagnosis of an arbovirus infection. Antibodies to arboviruses may be detected from day 3 – 7 after symptom onset. If initial antibody tests are negative, it is recommended to test a convalescent blood sample (collected two weeks after the acute phase of infection) to demonstrate seroconversion or the lack thereof. Laboratory findings should be considered in the light of the patient’s clinical findings and the possible exposure history.
Notifiable medical conditions
Rift Valley fever and Crimean-Congo haemorrhagic fever in humans are Category 1 notifiable medical conditions in South Africa. Other endemic, or non-endemic arboviral infections are listed as Category 3 notifiable medical conditions in the country.
