Cardioversion with drugs or synchronized direct current shock is most likely to be successful in younger patients and those with short duration of fibrillation. Fifth disease, or erythema infectiosum, is the most familiar clinical manifestation of parvovirus infection. The infection is caused by the B19 strain, one of the smallest known pathogenic viruses. Although other parvovirus strains infect animals, the B19 strain replicates only in human erythrocyte precursors. About one half of the population have IgG antibody by 15 years of age, and more than 90 percent have been exposed to infection by old age.
Infection is believed to be by droplet spread.
The secondary rash on the trunk and arms has a lacy reticular pattern and may be trivial or persist for weeks. In adults, the facial rash is uncommon, but joint symptoms may be severe. In rare cases, parvovirus infection causes transient aplasia, especially in children with underlying hematologic conditions such as sickle cell anemia or hereditary spherocytosis. In pregnant women, parvovirus infection is particularly dangerous between 20 and 28 weeks of gestation. Up to 10 percent of such cases result in stillbirth, but infants who survive do not appear to have any sequelae or increased vulnerability to hematologic disorders.