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Target organ: bone marrow erythroid precursors
High-level viremia occurs about 1 week after inoculation, Fever, malaise and myalgias last several days. Respiratory shedding of virus.
Shortly after infection, specific IgM and IgG response occurs
Fall in hemoglobin
About 10 days later: maculopapular rash, arthralgias, no viral shedding; immune complex disease
Sudden onset of red cheeks, fever, maculopapular rash (for weeks); rate of secondary spread is about 30%
Asymptomatic infection common
About 60% of adults are antibody positive
Patients with sickle cell disease, spherocytosis, thalassemia may develop aplastic crises
Immunocompromised children: prolonged infections
Spread by respiratory droplets; nosocomial transmission occurs
Isolate children with chronic anemia and febrile aplastic crisis
Don't isolate children with fifth disease
Symptoms: mild rash, fever, lymphadenopathy
Asymptomatic infection common (cannot use history for immunity)
Hemorrhagic complications in children: (low platelets vascular damage)
Symptoms are more pronounced in adults, arthralgia, arthritis (in females)
fingers, wrists, knees
Disease not more severe in immunocompromised
Timing
· 1st, early 2nd trimester
· 1- 2 months: 50% with fetal abnormalities
· 4th month: 10% with single fetal abnormality
Spectrum
· Cataract, congenital heart disease (PDA, PS), glaucoma, deafness, thrombocytopenia, diabetes
Fetal infection from maternal viremia
Pathogenesis unclear; mitotic arrest?
Less contagious than measles
Post-vaccine era: mini epidemics occur among susceptibles
Transmission: respiratory droplets; babies shed virus for many months despite antibodies
Immunity imperfect
· Reinfection without viremia common especially after vaccination
· Nevertheless highly successful vaccine
Acute/convalescent antibody titers
· Falling titer indicates that congenital infection is unlikely
IgM can occur in reinfection
To diagnose congenital infection: match exam to lab results notify CDC; PCR