Parvovirus B19 Infection and its Association to Autoimmune Disease

Human parvovirus B19, a relatively new virus, was discovered in 1975. Parvo B19 is a small, icosahedral, nonenveloped single stranded DNA virus with a genome of 5600 nucleotides. The cellular receptor is the P antigen, expressed on most erythroid progenitor cells, erythrocytes, megakaryocytes, endothelial cells, placental cells, and fetal liver and heart. Those who lack the P antigen are not at risk for parvo B19 infections. Parvo B19 encodes three major proteins: VP1 and VP2 of 84,000 and 58,000 d respectively, which are structural proteins, NS1 and two small amino acids, which are nonstructural proteins. Generally, most parvovirus B19 infections pass unnoticed without any clinical symptoms. The infection is biphasic, consisting of a viremic phase and an antibody response phase. During the viremic phase, symptoms range from being asymptomatic to having flu-like symptoms. The second phase of the infection is associated with rash, arthalgias, and arthritis. The virus resides in nasal and oropharyngeal tissue, and during viremia, the person is infectious via nasal and oral secretions. No viral DNA is detected in urine or feces. Diagnosis of an acute parvo infection is made by IgM serology. There is a brief window of opportunity in which the diagnosis can be determined because it has been estimated that 40%-80% of the adult population has already been exposed.