Case27 - Parvovirus

Case27 - Parvovirus - Lydyard, Peter; Cole, Michael;...

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1. What is the causative agent, how does it enter the body and how does it spread a) within the body and b) from person to person? Causative agent Parvovirus B19 belongs to the family of viruses known as the Parvoviridae . These are characterized by having a small single-stranded DNA genome. Parvovirus B19 belongs to the Erythrovirus genus within the subfamily Parvovirinae (and is therefore sometimes referred to as ‘erythrovirus’). The suffix ‘B19’ is somewhat spurious, arising from the coding of the par- ticular serum in which this virus was first identified, that is there are no parvovirus A or B1–18 viruses. There are, however, three recognized genotypes of B19 that differ slightly in their DNA sequence but behave similarly in terms of the clinical consequences of infection. Entry and spread within the body Infection is acquired via the respiratory route. About 6 days after infection, virus is found within the bloodstream, that is there is a viremic phase, which lasts about 6 days. Spread from person to person About 1 week after infection, at the time of the viremia , virus is detectable within the throat, and is shed from the respiratory tract, which represents the common route of spread. However, there is also a possibility of trans- mission via blood and blood products if blood donation is made at this stage of infection. Virus in the maternal bloodstream will also gain access to, and may cross, the placenta, giving rise to fetal infection in utero . Case 27 Parvovirus A 25-year-old teacher, who was 12 weeks pregnant, went to see her doctor as she had developed an extensive erythematous rash on her face, trunk, and limbs (Figure 1). She was also feeling feverish, and had noticed some aching in her wrists. A blood sample was sent to the laboratory, and the following results were received: rubella IgG -positive, IgM -negative; parvovirus B19 IgM-positive; parvovirus B19 DNA-positive. The unequivocal interpretation of these results was that the patient was suffering from an acute infection with parvovirus B19. Figure 1. Leg rash. © Lydyard, Peter; Cole, Michael; Holton, John; Irving, Will; Porakishvili, Nino; Venkatesan, Pradhib; Ward, Kate, Jan 01, 201 Garland Science, Hoboken, ISBN: 9780203856871
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Epidemiology Infection has been described worldwide. In temperate climates, while infection may occur throughout the year, it is more common in late win- ter/spring and early summer. Large-scale epidemics have a periodicity of about every 4–5 years. These are often based in primary schools, where over 50% of children may become infected, which also results in infection of susceptible adults such as parents and teachers. 2. What is the host response to the infection and what is the disease pathogenesis? IgM antibodies to the virus can be detected in the bloodstream about 9 days after infection, but the IgG antibody response is not detectable for 2–3 weeks. The appearance of IgM anti-parvovirus antibodies coincides with a decline in viral titers in blood. The IgM levels peak after a few days,
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This note was uploaded on 09/14/2011 for the course PHARM mb taught by Professor Staff during the Spring '11 term at UCSD.

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Case27 - Parvovirus - Lydyard, Peter; Cole, Michael;...

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