Parvo-viruses are amongst the smallest DNA-containing viruses capable of infecting mammalian cells.(1)
Parvovirus B19 causes mild symptoms in immunocompetent individuals, although it is often associated with chronic conditions in immunosuppressed patients.(2)
Can Parvovirus B19 Be Chronic?
The most common condition associated with parvovirus B19 or fifth disease is erythema infectiosum (also known as ‘slapped cheek syndrome’) in children.3 In healthy immunocompetent adults, B19 leads to acute asymmetric polyarthropathy. Parvovirus B19 displays tropism in response to erythroid progenitor cells that cause the transient aplastic crisis in individuals who have an underlying hemolytic disorder. While in patients who are immunocompromised persistent B19 infection is likely to manifest as red cell aplasia or chronic anemia.(1)
The immature immune response of the fetus will lead to fetal death in utero, hydrops fetalis, or development of congenital anemia in response to B19 infection. Parvovirus B19 has also been shown to be the causative agent in a variety of clinical syndromes. Still, due to the shared nature of the disease, the casualty is often difficult to infer.1 Additional reports also suggest that B19 parvovirus infection is also associated with cardiovascular diseases such as myocarditis in both adults and children. It has also shown an association with several liver diseases such as acute and chronic hepatitis, acute fulminant liver failure, and autoimmune hepatitis.3
The diagnosis is primarily based on the detection of specific antibodies by advanced techniques such as ELISA and PCR or dot blot hybridization that detects specific viral DNA. The use of immunoglobulins against persistent infection has shown promising results in reducing viral and therefore resolving anemia.(1)
Is Parvovirus B19 A DNA Virus?
Parvovirus B19 has a relatively simple structure that is composed of only two proteins along with a single-strand DNA molecule. The non-enveloped particles of the virus are approximately 22 to 24 nanometer in diameter and possess icosahedral symmetry. Both the empty and full capsids can be seen on electron microscopy or negative staining of the virus. Mature virus particles are composed of 60 copies of capsomer with both the negative and positive DNA strands packaged together. The surface of B19 has a surface that is significantly different from other parvoviruses in terms of absent prominent spikes on the threefold icosahedral axes that are involved in recognition and antigenicity. This structure of DNA (with the absence of a lipid envelope) makes it extremely difficult to inactivate the virus physically. The B19 virus is stable at 56 degrees Celcius for around 60 minutes remaining unaffected by liquid solvents. However, the inactivation can be achieved by using stronger solvents such as formalin and beta propriolactone and also by inducing gamma irradiation.(1)
Health Risks Of Parvovirus B19 Infection
B19 parvovirus infection is a global problem with incidents reported throughout the year in all age-groups. B19 DNA is also found in respiratory secretions of affected individuals that are involved in the transmission of the disease. Studies show that after intranasal inoculation, the condition became positive after 5-10 days. By the time the onset of arthralgia or rash, the serum had already been demonstrated negative for 1-5 days.(2)
The presence of IgG antibodies has shown a reduction in the risk of infection. When volunteers were inoculated with the B19 virus, only one of four positive IgG volunteers showed signs of infection, whereas four out of five IgG negatives were affected with the virus. The virus can be effectively transmitted after close contact exposures. The secondary attack rate is also as high as 50% in susceptible household patients. The outbreak is primarily in the form of direct transmission from person to person contact, fomites, and large-particle droplets or through small-particle droplets. The B19 virus can also pass through the transmission of blood during the treatment when the clotting factor concentrates even after steaming or heating the blood. The use of infected needles has also shown transmission of the virus from the infected to a healthy person. Recent infections can be tested by IgM antibody assay by capture-antibody radioimmunoassay or enzyme immunoassay in approximately 90% of cases.(2)