ADENOVIRIDAE FAMILY AND THEIR MEDICAL SIGNIFICANCE

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Adenoviridae family is made up of five viral genera which are Mastadenoviridae (which contain viruses that infect humans and other mammals); Aviadenovirus (which contain viruses that infect birds); Atadenovirus (which include viruses that infect ruminants, birds, and reptiles); Siadenovirus (which include viruses that infect amphibians, reptiles and birds); and Ichtadenovirus (which include viruses that infect fish). Adenoviruses are one of the major viruses in this family; and they have a worldwide distribution. Adenoviruses have an icosahedral shape, and they have no envelope. They measure between 80-110 nm. Adenoviruses are resistant to ether but sensitive to formalin and lipid solvents. They generally replicate in the nucleus and are released through the lysis of infected host cells. There are several serotypes of adenoviruses that cause infection in humans and other mammals. Adenoviruses cause several febrile illnesses in man and animals.

Some of the clinical symptoms of adenovirus infection in humans include respiratory diseases, infantile gastroenteritis and conjunctivitis. Adenoviruses may also cause disease in the urinary tract of humans. Most adenovirus infection is asymptomatic in infected individuals. The major routes of entry of adenovirus into the body of human hosts include the mouth, the nasopharynx, and the ocular conjunctiva. The virus replicates in the epithelial cells of the eye conjunctiva, respiratory tract and the gastrointestinal tract; and as aforementioned, most clinical cases of adenovirus infection are covert in nature (i.e., they do not produce apparent clinical symptoms). The incubation period of adenovirus infection is between 2-5 days; and patients become infectious when they are symptomatic. Adenovirus infections occur worldwide in humans as well as in a variety of animals. People at risk of infection with adenoviruses include young children, infants, the immunocompromised host and people in overcrowded military camps.

The major routes of transmission of adenoviruses in human population include the faecal-oral route and the respiratory route. Human infection with adenoviruses induces a lifelong immunity in infected hosts; and the likelihood of a re-infection with the virus is unlikely in individuals who have been previously exposed or infected. However, there is no specific treatment for adenovirus infection since most adenovirus infections in humans are asymptomatic and self-limiting in nature. Preventive measures for adenovirus infection depend on maintaining proper personal hygiene especially hand washing. The adenoviruses are of immense medical importance because they could serve as vectors for vaccination purposes and they have also been employed in gene therapy techniques. The use of adenovirus for these purposes is because adenoviruses hardly integrate their genome into the chromosome of their host cells; and the virus is one of the most studied viruses due to its apathogenic nature. They can be easily grown in cell culture in vitro; and adenoviruses have a higher stability than other DNA-containing viruses.

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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