Chickenpox physical examination

Overview
The diagnosis of varicella is primarily clinical. In a non-immunized individual with typical prodromal symptoms associated with the appropriate appearing rash occurring in "crops", no further investigation would normally be undertaken.

If further investigation is undertaken, confirmation of the diagnosis can be sought through either examination of the fluid within the vesicles, or by testing blood for evidence of an acute immunologic reposnse. Vesicle fluid can be examined with a Tsanck smear, or better with examination for direct fluorescent antibody. The fluid can also be "cultured", whereby attempts are made to grow the virus from a fluid sample. Blood tests can be used to identify a response to acute infection (IgM) or previous infection and subsequent immunity (IgE).

Prenatal diagnosis of foetal varicella infection can be performed using ultrasound, though a delay of 5 weeks following primary maternal infection is advised. A PCR (DNA) test of the mother's amniotic fluid can also be performed, though the risk of spontaneous abortion due to the amniocentesis procedure is higher than the risk of the baby developing foetal varicella syndrome.

Incubation and prodrome
The incubation period for varicella is 14 to 16 days after exposure to a varicella or a herpes zoster rash, with a range of 10 to 21 days. A mild prodrome of fever and malaise may occur 1 to 2 days before rash onset, particularly in adults. In children, the rash is often the first sign of disease.

Chickenpox in unvaccinated people
The rash is generalized and pruritic (itchy). It progresses rapidly from macules to papules to vesicular lesions before crusting. The rash usually appears first on the head, chest, and back then spreads to the rest of the body. The lesions are usually most concentrated on the chest and back.

In healthy children, varicella is generally mild, with an itchy rash, malaise, and temperature up to 102°F for 2 to 3 days. Adults are at risk for more severe disease and have a higher incidence of complications. Recovery from primary varicella infection usually provides immunity for life. In otherwise healthy people, a second occurrence of varicella is uncommon and usually occurs in people who are immunocompromised. As with other viral infections, re-exposure to natural (wild-type) varicella may lead to re-infection that boosts antibody] titers without causing illness or detectable viremia.

Chickenpox is vaccinated people
Chickenpox in people who are vaccinated is referred to as breakthrough varicella. Breakthrough varicella is infection with wild-type VZV occurring in a vaccinated person more than 42 days after varicella vaccination. Breakthrough varicella is usually mild. Patients typically are afebrile or have low fever and develop fewer than 50 skin lesions. They usually have a shorter illness compared to unvaccinated people who get varicella. The rash is more likely to be predominantly maculopapular rather than vesicular. However, 25%-30% of persons vaccinated with 1 dose with breakthrough varicella have clinical features typical of varicella in unvaccinated people.

Since the clinical features of breakthrough varicella are often mild, it can be difficult to make a diagnosis on clinical presentation alone. Laboratory testing is increasingly important for confirming varicella and appropriately managing cases and their contacts. There is limited information about breakthrough varicella in persons who have received two doses of varicella vaccine, though it appears to occur less frequently among people vaccinated with two doses of varicella vaccine compared to persons who have received a single dose of varicella vaccine.