We review 2 important viral infections in this article. One, parvovirus, poses a major threat to the fetus. The second, varicella, poses less risk to the fetus but significantly greater risk to the mother. We focus on the epidemiology, clinical presentation, diagnosis, and management of each infection.
Parvovirus infection and its risks to the fetus
CASE #1 Pregnant teacher exposed to fifth disease
A 28-year-old primigravid woman at 16 weeks’ gestation works as an elementary school teacher. Over the past 3 weeks, she has been exposed to 4 children who had fifth disease. She now requests evaluation because she has malaise, arthralgias, myalgias, fever of 38.2°C, and a fine lacelike erythematous rash on her trunk, arms, and cheeks.
- What is the most likely diagnosis?
- What diagnostic tests are indicated?
- Is her fetus at risk?
Epidemiology of parvovirus
Parvovirus B19 is a small, single-stranded DNA virus. It is highly contagious and is transmitted primarily by respiratory droplets. Transmission also can occur via infected blood, for example, through a blood transfusion. The incubation period is 10 to 20 days. Among adults, the individuals at greatest risk for infection are those who have close contact with young children, such as parents, day-care workers, and elementary school teachers. With sustained exposure in the household or classroom, the risk of seroconversion approaches 50%.1 Approximately 50% to 60% of reproductive-aged women have evidence of prior infection, and immunity is usually lifelong.
Clinical manifestations
The classic presentation of parvovirus infection is erythema infectiosum, also called fifth disease. This condition is characterized by a “slapped cheek” facial rash, malaise, myalgias, arthralgias, and low-grade fever. A fine lacelike rash often develops over the torso. In adults, the characteristic rash may be absent, and the most common presentation is a flu-like illness with joint pains.1,2 In children and in adults with an underlying hemoglobinopathy, parvovirus can cause transient aplastic crisis, and patients present with signs of a severe anemia, such as dyspnea, pallor, and fatigue.
Although parvovirus infection usually poses no serious risk in otherwise healthy children and adults, it can cause major fetal injury when the pregnant woman is infected early in pregnancy. The principal manifestation of fetal infection is hydrops. Hydrops primarily results when the virus crosses the placenta and attaches to the P antigen on the surface of red cell progenitors in the fetal marrow, causing an aplastic anemia with resultant high-output congestive heart failure. The virus also may directly injure the fetal myocardium, thus exacerbating heart failure. Other manifestations of congenital parvovirus include thrombocytopenia and hepatitis.3
The severity of fetal injury is inversely proportional to the gestational age at the time of maternal infection. When primary maternal infection occurs in the first trimester, the frequency of fetal hydrops is 5% to 10%. If infection develops in weeks 13 to 20, the risk of hydrops decreases to 5% or less. If infection develops beyond week 20, the incidence of fetal hydrops is 1% or lower.2
Continue to: Diagnostic steps...