Viral infection in a child: Parvovirus B19 Flashcards
Define parvovirus B19.
Single stranded DNA virus of the family parvovirdae. Induces immune complex formations that deposit in joints of the skin, causing ‘erythema infectiosum’. It also infects erythoblastoid percursors in the bone marrow.
Explain the aetiology of parvovirus B19.
The incubation period is 4-14 days. Duration is from 3-7 days prodrome then rash for 1-4 days; then evanescent rash over 1-3 weeks followed by arthropathy.
The virus requires the P blood antigen receptor (also known as globoside) to enter the cell. Rare individuals who lack the P antigen are immune to parvovirus B19 infection. Once inside the host cell, viral DNA enters the nucleus.
The 3’ end of the DNA strand folds back on itself, forming a hairpinlike bend that functions as a self-primer for viral DNA replication. The virus is cytotoxic to host cells.
Summarise the epidemiology of parvovirus B19.
The infection occurs in all ages and is more common in the winter and spring.
What are the signs and symptoms of Parvovirus B19?
Prodrome: Infection spread by respiratory secretion and droplets. Then low-grade fever, headache, and coryza 7 days after exposure.
Exanthematous phase: A number of days; bright red macules on the face with ‘slapped-cheek’ appearance (also, peri-oral pallor). The rash spreads to the limbs sparing the palms and soles. It is more intense with exposure to sunlight, heat, exercise, and stress.
Other features: Other patterns of illness include asymptomatic infection, aplastic crisis, foteal hydrops (from maternal infection).
What are appropriate investigations for parvovirus B19?
Clinical: Characteristic rash.
Parvovirus serology (anti–parvovirus B19 immunoglobulin M [IgM] and immunoglobulin G [IgG] antibodies) can be determined using enzyme-linked immunoassay (ELISA), radioimmunoassay, or immunofluorescence.
PCR testing for parvovirus can also be done.
What is the management for parvovirus B19?
Supportive, give antipyretics for fever.
Give RBC transfusion for aplastic crisis.
What are complications associated with parvovirus B19?
Intrauterine infection
Aplastic crisis
Immunocytopenia
What is the prognosis for some of the complications associated with parvovirus B19?
Erythema infectiosum: This is a self-limiting condition in immunocompetent patients.
Arthropathy: There are no long-term sequelae.
Transient aplastic crisis: This is usually transient, lasting no more than two weeks in otherwise healthy individuals; it responds rapidly to treatment if required.
Immunocompromised patients: The treatment of pure red cell aplasia with immunoglobulin is frequently ameliorative and often curative.
What is the prognosis of parvovirus B19?
The most common consequence of B19 infection in the compromised person is pure red cell aplasia, resulting in chronic or recurrent anaemia with reticulocytopenia. The majority of compromised people have pre-existing antibody to B19 and are not at risk.
