Reports suggest that 20% of cases of B19 infection from India are reported in patients with hematological disorders with aggravation of anemia.(1)
B19 parvovirus has gained the status of an expanding and emerging virus as its clinical spectrum has increased over the decades.(1)
Who Is At Risk For Parvovirus B19 Infection?
The parvovirus b19 infection is widespread and the manifestations vary from individual to individual depending upon the immunological and hematological status of the person. In a healthy child, b19 can cause erythema infectiosum that is an innocuous rash illness. In adults, the virus usually leads to acute symmetric polyarthropathy which mimics rheumatoid arthritis. Since the parvovirus b19 has a tropism to erythroid progenitor cells an infection in individuals with an underlying hemolytic disorder leads to transient aplastic crisis. In an immunocompromised person, persistent b19 infection manifests as red cell aplasia and chronic anemia. Likewise, in a fetus an immature immune response will make them more susceptible to infection that causes intrauterine fetal death, hydrops fetalis, or development of congenital anemia. Diagnosis of the disease is done based on the detection of antibodies specific to the virus by ELISA or dot blot hybridization and PCR.(3)
Infection in the healthy host will lead to asymptomatic infection in both children and adults. Asymptomatic seroconversion can be seen in people who have undergone recent transfusions for hemolytic anemia. Other conditions that make an individual at more risk to develop complications related to b19 parvovirus are:
Cardiovascular Infliction- acute inflammatory myocarditis leading to ventricular dysfunction and secondary myocyte necrosis.
Renal Infliction- glomerulonephritis, focal segmented glomerulosclerosis, or collapsing glomerulopathy.
Neurological Affliction- encephalitis, mononeuropathy multiplex, and Guillain-Barre syndrome.
Placental Infection By b19 Virus- leads to hydrops fetalis and fetal anemia along with spontaneous abortions.
Hematological Affliction- they can present as an aplastic crisis that targets erythroid progenitor cells causing lytic infection and hence severe anemia. Leukemia in children with ALL b19 infection will precipitate and complicate the course of the underlying disease-causing persistent anemia and requiring prolonged duration of induction therapy.
Cutaneous Affliction- they are uncommon such as a rash from erythema infectiosum to a purpuric –petechial eruption, pseudo-erysipelas, and scleroderma.
Organ Transplantation And Other Organs – due to b19 infection there may be problems while transplanting organs such as heart, liver, or kidneys. Also, transfusion of blood or blood products from an infected donor will transmit the disease leading to high titer viremia.(2)
Is There A Blood Test For Parvovirus B19 Infection?
Although b19 can be detected in serum by EM, B19 antigen ELISA and hemagglutination but the most common method used is the isolation of the virus by direct hybridization or PCR. Direct hybridization is a test sensitive enough to detect b19 levels in an acute transient phase of the disease and pure red cell aplasia due to b19 infection in immunosuppressed patients due to which lower levels of viremia will be missed. With the advent of PCR, DNA can be easily detected in the serum and tissue samples due to increased sensitivity. DNA can be detected even after long periods in serum, synovial membranes, and bone marrow even in healthy individuals. Therefore, low levels of b19 DNA alone cannot be used to diagnose acute infection by parvovirus b19 infection. B19 based DNA assays play a crucial role in the diagnosis of the infection in patients of transient aplastic crisis before the antibody response.
It is also important to diagnose b19 infection in patients of chronic anemia due to immunosuppression, where there is the failure to show immune response along with erythema infectiosum and b19 induced arthropathy. Due to the inability of b19 to replicate in culture systems, viral capsids were initially purified from serums with high virus titers and used for antibody tests. IgM capture essays can reliably detect a current or recent infection in immunocompetent individuals. Detection of NS1- specific antibodies also needs to be done especially in individuals with arthritis or persistent b19 infection since prolonged viremia has been shown to lead infection of cells outside the erythroid lineage.(3)