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Human parvovirus (HPV) B19 was first
discovered in 1975 in serum specimens from healthy blood donors.1 Parvovirus
B19 belongs to the genus Parvovirus, an autonomously
replicating, small single-stranded DNA virus. It is the infectious
agent of a number of clinical syndromes, including erythema infectiosum (formerly
known as fifth disease), acute arthritis, and aplastic
crises in patients with congenital hemolytic anemia.2-4 When
acquired by a pregnant woman, it can lead to spontaneous abortion,
intrauterine fetal hydrops, and stillbirths.5,6
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The Parvoviridiae family includes two genera
of vertebrate viruses and one genus of invertebrate viruses. Only
HPV B19 infects humans and is known to be associated with disease.
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Parvovirus infections are most commonly recognized in school-age
children. Infections can be sporadic, although epidemics occasionally
do occur, most commonly in late winter or spring. Approximately
70% of recognized infections occur in children between
5 and 15 years of age. Children younger than 5 years have a seroprevalence
of 2% to 9%, children 5 to 18 years old have a
seroprevalence of 15% to 60%, and adults have
a seroprevalence of 30% to 60%.7 Secondary
attack rates are approximately 50% within households and
variable in school outbreaks.7Males and females
are equally affected with erythema infectiosum, whereas arthritis
is more common in females.8
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Because the virus is present in respiratory secretions of viremic
patients, transmission occurs most frequently via respiratory droplets.
Patients with erythema infectiosum are infectious before, not during,
the rash, whereas patients with an aplastic crisis are likely to
be most infectious at the time of the acute presentation.9 Parvovirus
is rarely transmitted by transfusion of blood or, more commonly,
clotting factor concentrates. Vertical transmission from mother
to infant also occurs.
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The virus enters cells by binding to a receptor called globoside
or erythrocyte P antigen. Individuals lacking this receptor cannot
be infected with HPV B19.10 Intranasal infection
of HPV in human volunteers resulted in fever, malaise, and itching
approximately 1 week after infection. During this period, susceptible
volunteers were viremic and had respiratory shedding. During the
second week of infection, IgM developed, and there was reticulocytopenia.
Development of arthritis or rash during the third week of infection coincided
with the development of an IgG response.11 Therefore,
the pathogenesis in patients with erythema infectiosum or arthritis
is believed to be secondary to immune complex disease. The pathogenesis
of some of the more serious complications is related to the viral
effect on erythrocyte precursors, leading to pronormoblast arrest.
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Clinical Manifestations
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Many infected individuals have no recognizable symptoms; however,
when a clinical syndrome does occur, it causes erythema infectiosum
(EI), also known as fifth disease, a common childhood
exanthem. It is characterized by a prodromal illness, usually consisting
of ...