PARVOVIRIDAE FAMILY (Human Parvovirus B19)

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Parvoviridae family has six (6) genera of virus which include Parvovirus, Contravirus, Erythrovirus, Dependoparvovirus (formerly, Dependovirus), Densovirus and Iteravirus. Parvovirus or the human parvovirus B19 is the major viral agent in this family of virus because it causes infections in humans. The family Parvoviridae also contains viruses that cause viral infection in animals. The human parvovirus B19 is a small, non-enveloped virus with a linear, single-stranded DNA (ssDNA) genome. It is an Erythrovirus in the Parvoviridae family. Parvovirus measures between 18-26 nm in diameter; and they have a single-stranded DNA (ssDNA) genome.

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Their replication is within the nucleus of their host cell (specifically the erythroid precursor cells responsible for erythrocyte production in the bone marrow). Viruses in the Parvoviridae family are resistant to ether but sensitive to chlorine compounds, formalin and ultraviolet (UV) light. Viruses in the Parvoviridae family lack envelope (i.e., they are naked viruses), and they have an icosahedral shape or structure. They are relatively stable at high temperature. Viruses in the Parvoviridae family are released through the lysis of infected host cell(s) since they lack envelope. Human parvovirus B19 causes erythema infectiosum in children and aplastic crises in sickle cell and anaemic patients. Erythema infectiosum is also called the “fifth disease”.

Fifth disease is usually characterized clinically as the onset of an erythematous rash (known as slapped cheek syndrome) on the face and skin of the infected child.It is called “slapped cheek syndrome” because the skin and especially the cheeks of infected children appear as though they have been slapped on both sides. There is rapid destruction of the red blood cells (RBCs) of anaemic or sickle cell individuals infected with the virus (human parvovirus B19); and this is usually due to its replication in the blood cells or bone marrow of the infected persons. Parvovirus B19 viral infection has also been associated with spontaneous abortion in humans.

The incubation period of human parvovirus B19 infection is usually between 12-18 days; and the disease onset is usually characterized by the appearance of a maculopapular rash all over the body of infected children. Fifth-disease is a rash-causing childhood disease common in toddlers and children of such age group; and it is usually benign in nature but characterized by maculopapular rashes all over the body. Upper respiratory symptoms, headache, fever and malaise are other associated signs of the disease. Its transmission route is through infected blood and the respiratory route. Parvovirus infects mostly children, and the disease has a worldwide prevalence.

However, immunocompromised individuals, pregnant women and people with haemolytic anaemia are also at risk of contamination. No specific prophylaxis or vaccine exists for human parvovirus infection; and there’s also no specific antiviral treatment for the disease. Since fifth disease is usually self-limiting in affected children, most treatment and management of the disease is usually based on supportive therapy. However, fever-reducing therapeutics (i.e., antipyretics) can be administered to infected children to take care of the fever and headaches that is associated with the disease (i.e., fifth disease caused by human parvovirus B19 infection).       

Further reading

Acheson N.H (2011). Fundamentals of Molecular Virology. Second edition. John Wiley and Sons Limited, West Sussex, United Kingdom.

Brian W.J Mahy (2001). A Dictionary of Virology. Third edition. Academic Press, California, USA.

Cann A.J (2011). Principles of Molecular Virology. Fifth edition. Academic Press, San Diego, United States.

Carter J and Saunders V (2013). Virology: Principles and Applications. Second edition. Wiley-Blackwell, New Jersey, United States.

Dimmock N (2015). Introduction to Modern Virology. Seventh edition. Wiley-Blackwell, New Jersey, United States.

Kudesia G and Wreghitt T (2009). Clinical and Diagnostic Virology. Cambridge University Press, New York, USA. 

Marty A.M, Jahrling P.B and Geisbert T.W (2006). Viral hemorrhagic fevers. Clin Lab Med, 26(2):345–386.

Strauss J.H and Straus E.G (2008). Viruses and Human Diseases. 2nd edition. Elsevier Academic Press Publications, Oxford, UK.

Zuckerman A.J, Banatvala J.E, Schoub B.D, Grifiths P.D and Mortimer P (2009). Principles and Practice of Clinical Virology. Sixth edition. John Wiley and Sons Ltd Publication, UK.

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