Parvovirus

Question 1

What is parvovirus and how does it affect cells

Answer 1

Parvovirus B19 is a non enveloped single stranded DNA virus - infects animals and humans
Infects rapidly dividing cells and is cytotoxic to erythroid progenitor cells. It may also cause apoptosis

Question 2

What % of woman are susceptible
What is the rate of infection in pregnancy
How is at high risk

Answer 2

Antibodies to B19 are found in 30 to 60 percent of adults 40% of woman susceptible

The incidence of acute B19 infection in pregnancy is 3.3 to 3.8 percent this risk varies among different occupational groups.
The highest infection rates occurred in schoolteachers (16 percent), followed by day care workers and homemakers (9 percent each)

Also at risk is mums of children with parvovirus

Question 3

How does it present

Answer 3

common childhood illness. Asymptomatic or mild infection occurs most often when B19 affects immunocompetent adults
Parvovirus B19 causes erythema infectiosum (EI), also known as fifth disease
Children have the slapped cheek appearance (adults don’t)
Arthropathy, 1-2 weeks
Possible aplastic crisis (if hx chronic anaemia)

Question 4

Transmission and incubation

Answer 4

Person to person via the respiratory route
And via fomites
Viremia starts 6 days after exposure and lasts for 1 week - infected people are contagious before the onset of symptoms
Probably not infectious once the rash and arthralgias start

Question 5

Risk to fetus

When is it worst

Answer 5

fetal loss or hydrops fetalis

First 20/40 10% fetal death if proven infection
(if exposed 1%)
After 20 weeks 0%

3% hydrops
<1% non specific congential abnormalities

Of the babies with hydrops 
30% spontaneously resolves 
30% death within a week (overall 0.6%) 
If IUT - 30% resolution 
6% death after IUT

Question 6

How to manage infection in pregnancy

Answer 6

Maternal infection before 20 weeks gestation
USS examination at 1-2 week intervals for 12 weeks
If no fetal abnormality after 30 weeks thn no further action is required
If anaemia is identified then treat

No intervention prevents fetal infection of damage
TOP is not indicated as low risk of fetal damage
Amnio is not recommended
A fetoprotein levels are not recommended
Can test PCR on cord blood or liquor
Mild hydrops may actually have profound anaemia
MCA PSA is the way to monitor for anaemia

Question 7

What is the risk of infection after susceptible exposure?

Answer 7

at home 50%
at school or child care 20-30%
exposure in the community - 20%

Question 8

What % of pregnant woman are susceptible to infection?

Answer 8

40%

Question 9

What is the risk of vertical transmission?

Answer 9

50%

Question 10

If suspect - what tests?

Answer 10

IgG and IgM
IgM detectable within 1-3 weeks of exposure

IgG +
IgM -
immune

IgG +
IgM +
recent infection

IgG -
IgM +
? new infection

IgG -
IgM -
susceptible
- repeat in 2-4 weeks or if sx