The second group of parvoviruses, constituting the genus Parvovirus , do not require a helper virus for replication. The diseases caused by autonomous parvoviruses reflect their requirement for actively dividing cells. The human autonomous parvovirus, B19 virus, replicates in erythroid precursor cells and hence produces aplastic crisis in predisposed individuals with underlying hemolytic anemia or immunodeficiency. Other clinical manifestations of B19 virus infection are due to the host immune response to the virus. Clinical Manifestations Erythema Infectiosum Erythema infectiosum, also known as fifth disease, is the most common clinical manifestation of B19 virus infection.
Clinical symptoms develop in a biphasic fashion.
Some 7 to 8 days after infection, a prodromal influenza-like illness develops, characterized by headache, malaise, chills, and pyrexia. Individuals are then asymptomatic for a week. The second phase of illness occurs 17 to 18 days after infection, with the development of a mild febrile illness and a maculopapular rash. The rash initially has a discrete erythematous maculopapular appearance and then becomes reticular, disappearing in 1 to 3 weeks. Erythema infectiosum often resembles the rash of rubella.