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Tuesday, January 27, 2009

Picornaviridae

It is the largest virus family over 230 serotypes.
It can be classified into 5 genera :



Enterovirus
Human polioviruses 1-3 (serotypes=3)
Human hepatitis virus A (serotypes=1)

Rhinovirus
Human rhinoviruses 1-100 (serotypes=100)
Bovine rhinoviruses 1-2 (serotypes=2)

Aphthovirus
Foot-and-mouth disease virus 1-7 (serotypes=7)

Cardiovirus
Encephalomyocarditis (EMC), Mengo (serotypes=1)

Unassigned
Equine rhinoviruses 1-2, Cricket paralysis... (serotypes>3)

Morphology

Virions consist of a capsid. Virus capsid is not enveloped, round with icosahedral symmetry. The capsid is isometricand has a diameter of (22-)27-30 nm. Capsids appear round. The capsid consists of 12 capsomers.
Incomplete particles are common. They are devoid of nucleic acid characterized by capsids with dark centers in negative stain preparations.




Genome of Picornaviridae

Poliovirus virion RNA functions as an mRNA but does not have the methylated cap structure typical of eucaryotic mRNAs - it has a internal ribosome entry site or IRES which enables ribosomes to bind without having to recognize a 5' methylated cap structure.





The mRNA is translated into a single polypeptide (polyprotein), which is cleaved. The cleavages occur before translation is complete and are carried out by virally coded proteases.



Example of Picornaviridae: Rhinovirus (Common Cold)

Pathogenesis
- Infect the lower respiratory tract
- Trigger asthma exacerbation
- Short incubation of (2 -3 days)
- Over 100 Rhinoviruses.
- Mild upper respiratory viral infection




Symptoms
- Watery nasal discharge
- Congestion
- Sneezing
- Little / No fever


Preventions



Example of Orthomyxoviridae: Influenza (Flu)





Diseases related to respiratory system are spread more in crowded environment and enclosed spaces, such as buses. Transmission may also occur by direct contact, since the influenza virus may survive for hours, particularly in cold and in low humidity.

Morhology
Virions enveloped , pleomorphic and filamentous forms occur; spherical, or filamentous; 50-120 nm in diameter, or 20 nm in diameter; 200-300(-3000) nm long. Surface projections of envelope distinct; about 500 spikes (projecting 10-14 nm from the surface); dispersed evenly all over the surface.




Pathogenesis
The influenza A virus can infect humans, horses, birds, and pigs. Wild birds are the natural reservoir for influenza A viruses. The Influenza A virus is mainly spread by aerosols that get into the respiratory tract. The virus particles then attack the ciliated epithelial cells lining the respiratory tract, causing necrosis of the cells.




Prevention




Laboratory Diagnosis




Differences between Cold and Flu




Video of how influenza virus affect a human body!



Video of mutation of an antigenic shift in human genetic code!



**ALL IMAGES CLICK TO ENLARGE !!

Applications
http://pathmicro.med.sc.edu/mhunt/RNA-HO.htm
http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.052.htm
http://www.flufacts.com/about/cold.aspx
http://www.flufacts.com/treatment/default.aspx
http://www.virology.net/Big_Virology/BVRNAortho.html
http://www.youtube.com/watch?v=fW_YoQYqUzk
http://www.youtube.com/watch?v=01qwLckBLSM&feature=related



HELLO

5:09 PM