Parvovirus

Question 1

Characteristics

Size, genome, envelope?

Answer 1

Simplest, smallest, naked (no envelope), single-stranded DNA animal virus

Question 2

How does it replicate?

Answer 2

Replicate autnomously in rapidly dividing cells

Question 3

What is the virus that infects only humans?

Answer 3

Parvovirus B19

Question 4

How is it transmitted?

Answer 4

Mainly by body fluids, blood and vertically from mother to fetus

Question 5

When do the symptoms usually appear?

Answer 5

Within 4 days to 2 weeks after exposure

Question 6

What is the disease called?

Answer 6

Fifth disease - Ertyhema Infectiosum

Question 7

What are the 2 phases of the disease it causes?

Answer 7

1st phase - viraemic phase
* Virus present in upper respiratory tract
* Symptoms occur at the end of 1st week: fever, malaise, myalgia, chills, itching
2nd phase - mediated by immune complexes
- Rash in 1/3 of patients
- “Slapped cheek” appearance

Fifth Disease - Erythema Infectiosum

Question 8

Describe the pathogenesis of B19 infection

Answer 8

Targets human erythroid progenitor cells -> causes lysis of cells leading to anemia
Can also affect lymphocytes, granulocytes and platelets

Question 9

Who is at risk of B19 infection? What does it cause?

Answer 9

1. Chronic haemolytic anaemia: transient aplastic crisis
2. Immunocompromised: severe aplastic anaemia
3. Pregnant: severe anemia in fetus (1st trimester>2nd trimester)

Question 10

How to diagnose B19 infection?

Answer 10

• PCR rapid and specific (virus difficult to grow)
• Serology (IgM appears 4-7 days, IgG appears 7-10 days and persist for years)
  Pregnancy
• Mother: serology for IgM and IgG, PCR to detect B19 DNA in maternal serum
• Fetus: ultrasound screening for non-immune hydrops, percutaneous umbilical blood sampling

Question 11

How to treat?

Answer 11

• No known specific treatment
• Blood transfusion for transient aplastic crisis
• For fetal infection: watchful waiting, high-dose IgG therapy, intrauterine fetal transfusion