Parvovirus B19 (Erythrovirus)

Small Single-stranded, linear DNA; small size and genome render them very dependent on the host for replication. Naked icosahedral capsid viruses, which resist inactivation. Tropism for erythroid progenitor cells; we would see giant pronormoblasts (aka, lantern cells), which are the result of parvovirus infection. They are characterized by "Dog ear" projections and nuclear inclusion bodies Infection is **common, and can be asymptomatic. However, it can also produce fever and other nonspecific symptoms. There are no specific treatments or preventions for human parvovirus infection Infection has two stages: Febrile, infectious stage lasts from approximately day 7 to day 14. Rash and arthralgia, noninfectious stage lasts from approximately days 20-27. Viral entry is typically via respiratory droplets. Replication occurs in the upper respiratory tract. Viremia produces the fever, sore throat, chills, and other non-specific symptoms that may occur during the febrile infectious stage of illness. Viremia delivers the virus to the bone marrow, where it then infects the erythroid progenitor cells and replicates. This causes a pause in erythrocyte production that lasts about a week. Virus-specific antibodies, IgM and IgG antibodies, form, and viral load declines. Immune complexes begin to form – this ushers in the immune mediated, noninfectious stage of illness. This stage generally manifests differently according to age: Erythema infectiosum, aka, fifth disease, develops in children and adolescents. This is characterized by a rash that begins with a "slapped cheeks" pattern on the face that spreads to the torso and extremities. Polyarthritis develops in adults; some adults also develop rash. Infection is self-limiting and relatively benign in most cases. Two important exceptions to this: Transient aplastic crisis, aka, reticulcotypenia (low reticulocyte count) occurs in patients with chronic hemolytic anemia, such as sickle cell anemia. Hydrops fetalis (fluid accumulation in multiple body compartments) occurs when human parvovirus is transferred across the placenta. Newly discovered parvovirus. Infection is common, especially in young children; often present in co-infections. Often asymptomatic, but sometimes associated with:

• Acute lower respiratory illness with wheezing
• Gastroenteritis