Infectious agent:
The causative agent is human parvovirus B19.
Identification:
Clinical features :
Asymptomatic infection with human parvovirus B19 is common. In
children it causes a mild illness with
little or no fever but a striking redness of the cheeks, hence
the alternative name of ‘slapped cheek disease’. There may also be a lacy pink
rash on the trunk and limbs that fades within a week, but which
may recur over several weeks on exposure to heat or sunlight.
Headache, itch or common cold-type symptoms may also occur. In adults the rash
is often absent or atypical. They may have cold-type symptoms and sometimes painful
or swollen joints lasting two or three days. Parvovirus affects the development
of red blood cells. As a result several groups of people are at increased risk
of developing complications:
• infection in the first half of pregnancy can cause foetal
anaemia with hydrops foetalis. Foetal death occurs in less than ten per cent of
these cases
• persons with haemolytic anaemia may develop transient aplastic
crises, often in the absence of a rash
• immunosuppressed persons may develop severe chronic anaemia.
Method of diagnosis:
Diagnosis can be suspected on clinical grounds, particularly
during outbreaks. However, confirmation depends on demonstrating the presence
of specific IgM antibodies or seroconversion to specific IgG antibodies.
Comparison of the current antibody status against prenatal screening serology
for parvovirus is often useful in pregnancy. Specific IgM antibody titres
decline two to three months after infection while IgG levels, which appear two
weeks after infection, can persist indefinitely. Nucleic acid (PCR) testing and
electron microscopy can also be used to confirm foetal infection.
Incubation period:
The incubation period varies from four to twenty days.
Public health significance and occurrence:
Human parvovirus infection occurs worldwide and is a common
childhood disease. Outbreaks occur during winter and spring with epidemics
occurring every three to four years. Up to 50% of susceptible household contacts
and 10–60% of child care or school contacts may be infected during outbreaks.
Reservoir:
Humans.
Mode of transmission:
The virus is transmitted by contact with infected respiratory
secretions. It may be spread vertically from mother to foetus and rarely by
transfusion of blood products..
Period of communicability:
Children with erythema infectiosum are most infectious before
the onset of the rash and are probably not infectious after the rash appears. Patients
with an aplastic crisis are infectious for a week after the onset of symptoms. Immunosuppressed
persons with chronic anaemia due to infection may excrete virus for years.
Susceptibility and resistance:
Infection generally confers immunity. Serological surveys
suggest 5–15% of preschool children and 50–60% of all adults are immune.
Control measures:
Preventive measures:
There is no vaccine available. All people who are non-immune to parvovirus,
immunosuppressed, have
chronic haemolytic disorders, or who are pregnant are at
increased risk of complications. These people should be advised of the risk
that parvovirus infection may pose to them. They should avoid close contact
with children or adults in settings where parvovirus infection
may occur such as schools, child care centres and health care facilities. Strict
hand washing and separate eating utensils are also advised for these people.
Control of case:
There is no specific treatment required for uncomplicated
infection. Specialist advice should be sought if a
patient with immunodeficiency or a blood disorder contracts
parvovirus infection.
Control of contacts:
Intrauterine infection may rarely result in foetal hydrops or
death if infection occurs within the first 20 weeks of pregnancy. Medical
advice should be sought for pregnant women who have been in close contact with
a case of parvovirus infection. Specific antibody testing should be performed
to
determine the woman’s immune status to parvovirus.
Control of environment:
Not applicable.
Outbreak measures:
General public health measures include:
• advising high risk persons of relevant outbreaks
• advising patients and contacts to observe strict hand washing
after coughing, sneezing and before eating.
.sources
of information
·
The blue book: Guidelines
for the control of infectious diseases
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