Replication of viral genome and release of virus from infected cells lead to various complex effects on hosts cellular environment such as induction of DNA damage, hijack of cell cycle and apoptosis (killing of infected cells).B19V DNA has been found in a wide range of tissues in healthy and diseased individuals indicates the persistence of B19V infection. According to a clinical microbiology review published by Jianming Qiu "Persistence of viral DNA has been detected in up to 50% of biopsy specimens of the spleen, lymph nodes, tonsils, liver, heart, synovial tissues, skin, brain, and testes, for decades after infection. "Recovery from parvovirus B19 infection is achieved by production of IgM antibodies which are specific for virus and are generated 10–12 days after infection. After day 16, when signs of fifth disease (red rashes) and arthralgia (pain in joints) becomes apparent, specific anti B19 IgG is produced by immune cells. Production of serum anti B19 IgG keeps infection under control and facilitates the recovery of erythroid cell production in erythroid lineage cells that were targeted by parvovirus B19. Diagnosis
The "slapped cheek" appearance of the rash can be suggestive of fifth disease, however, the rash can be mistaken with other skin related disease or infections. Blood samples testing can be definitive in confirming diagnosis. Anti-parvovirus B19 IgM antibody serum assay is the preferred method to detect previous infection. An antibody assay uses antibodies designed to detect parvovirus antigen or protein in blood circulation. The assay can result positive one week after initial infection.
Negative results may prompt retesting in the future to rule out early sampling of blood serum. A positive result can also be indicative of an infection within the past two to six months. People acquire lifetime immunity if IgG antibodies are produced in response to parvovirus B19 exposure. Infection by parvovirus B19 can also be confirmed by isolation of viral DNA detected by PCR or direct hybridization. PCR Is considered significantly more sensitive to detecting viral antigen compared direct DNA hybridization. DNA hybridization assay can better detect variants of the parvovirus B19. There exists 3 biological similar genotypes of parvovirus B19, numbered one through three. The most common genotype circulating is genotype one. Laboratory tests can indicate complications of infection, including anemia, liver damage, and low platelet count. Transmission
Fifth disease is transmitted primarily by respiratory secretions (saliva, mucus, etc. ), but can also be spread by contact with infected blood. The incubation period (the time between the initial infection and the onset of symptoms) is usually between 4 and 21 days. Individuals with fifth disease are most infectious before the onset of symptoms. Typically, school children, day-care workers, teachers, and parents are most likely to be exposed to the virus. When symptoms are evident, the risk of transmission is small; therefore, symptomatic individuals do not need to be isolated. Vertical transmission from maternal infection may also occur, which can lead to hydrops fetalis due to the infections detrimental effects on red blood cell production. Treatment
Treatment is supportive, as the infection is frequently self-limiting.