Poxviridae

The poxviridae family of viruses is the largest and most complex of viruses that have been discovered to date.

Poxviridae are so large that it can be seen through a light microscope.

Poxviridae infects a wide range of hosts and there are two subfamilies which are chordopoxvirinae and entomopoxviridae.

Chordopoxovirinae subfamily covers all the human poxes, and can be further classified into orthopoxvirus and parapoxvirus genera.

You might wonder if chickenpox is caused by a virus from the poxviridae family. However, the answer is no, as the chickenpox virus is from the herpesviridae family. That's right, you've most likely had herpes before.

Physical Properties

Genome
-Contains a single molecule of linear double-stranded DNA, like a strand of DNA in a human cell.
-The complete genome is 130000-375000 nucleotides long.


Morphology
-Complex, oviod or brick-shaped nucleocapsid.

Envelope
-Orthopox are enveloped but parapox are not.

Lipids
-Lipids are present and located in the envelope.
-The composition of viral lipids and host cell membranes are similar.
-The lipids are host derived and synthesized de novo (during the early phase of virus replication) and are derived from plasma membranes.
-Viral membranes include glycolipids.


Replication/reproduction
-Similar to other Group 1 viruses, it integrates its DNA into the host cell's genome. However, it is unique in that it codes for its down genome replication machinery, instead of using the host's pre-existing machinery.



Host range
-Varies by specific virus; zoonosis is common but small pox only infects human beings.

Domain
-Viral hosts belong to the Domain Eucarya

Domain Eucarya
-Kingdom Animalia

Kingdom Animalia
-Phylum Chordata and Arthropoda

Phylum Vertebrata
-Subphylum Vertebrata
Class : Mammalia and Aves

Oncogenicity
May cause benign tumors( which is a tumor that lacks all 3 of the most severe and progressively worsening disease properties of cancer)

HERE is a picture of how a poxviridae looks like :




So How are pox virus transmitted?

They are commonly spread by direct contact. For example, smallpox virus can be found in the upper respiratory tract, and can spread when mucus droplets come into contact with wounds or skin lesions on another person. While it is highly contagious, the rate of spread is still relatively slow, because of the kind of contact that must occur before it can spread.

How does the immune response and the host defend itself after being affected before?

Infection by a pox virus results in cell-mediated immunity, people who are infected with small pox before are generally immune to the disease for the rest of their lives. This is the entire principle of vaccination.

In fact, the term "vaccination" was derived from the name "vaccinia", a poxvirus that was used to give people immunity to smallpox.