Parvoviridae

Question 1

Briefly discuss the basic structure and genomic organisation of parvoviridae.

Answer 1

non-enveloped, icosahedral symmetry, ssDNA
[Diagram]

Question 2

(a) ____________ is the most clinically significant parvovirus.
(b) State the genus of the virus mentioned above.

Answer 2

(a) Parvovirus B19
(b) Erythroparvovirus

Question 3

Briefly discuss the pathogenesis of Parvovirus B19.

Answer 3

🛸 The virus enters the body through the mucous membranes of the respiratory tract, where it initially replicates in the nasopharyngeal cells.
🛸 The virus then enters the bloodstream, leading to viremia.
🛸 From the blood, Parvovirus B19 spreads to the bone marrow where it infects erythroid progenitor cells in the bone marrow. The virus gains entry into these cells by binding to the P antigen (globoside) on the cell surface. [It may also infect erythroid progenitor cells in the foetal liver.]
🛸 Once inside the host cell, parvovirus B19 translocates its genome to the nucleus, where it undergoes replication and transcription.
🛸 New virions are then released from the infected cells, often causing cell lysis, which contributes to the symptoms of the disease.
🛸 The virus may also infect other cells e.g. endothelial cells, mycoardial cells, synovial cells and immune cells [monocytes/macrophages].

Question 4

How is Parvovirus B19 transmitted?

Answer 4

respiratory droplets released when an infected person coughs or sneezes

Question 5

Discuss the clinical presentation of Parvovirus B19.

Answer 5

🛸 Incubation period is ~ 1 week.
🛸 Erythema infectiosum: This is the most common manifestation in children, characterized by a “slapped cheek” rash on the face, which may spread to the body. It is usually accompanied by mild flu-like symptoms. [Image 1] [Image 2] [Image 3]
🛸 Arthropathy: In adults, especially women, parvovirus B19 can cause joint pain and swelling, known as polyarthropathy syndrome.
🛸 Transient aplastic crisis: In individuals with underlying hemolytic disorders (e.g. sickle cell disease), parvovirus B19 can cause a severe drop in red blood cell production.
🛸 Hydrops fetalis: Infection during pregnancy can lead to severe fetal anemia and hydrops fetalis, a condition characterized by abnormal accumulation of fluid in fetal compartments. [Image 4]

Question 6

laboratory diagnosis of Parvovirus B19

Answer 6

🧬 PCR
🧬 serology for IgG (paired) or IgM may also be used (ELISA or IFA)

Question 7

treatment/management of Parvovirus B19

Answer 7

🛸 no vaccine
🛸 treatment is supportive

Question 8

What is the most likely presentation of parvovirus infection in a healthy male?
(a) arthritis
(b) thrombocytopenia
(c) aplastic anemia crisis
(d) malar rash
(e) mild febrile illness

Answer 8

(e) mild febrille illness