Poxviruses, family Poxviridae, are responsible for a wide range of pox diseases in humans and other animals. Most notably variola virus (VARA), the cause of smallpox, was declared eradicated worldwide in 1980 by the World Health Organization. So what is the structure of poxvirus? And how many genus of poxvirus in the world?
What is the Structure of Poxvirus?
Poxviruses are brick or oval-shaped viruses with large double-stranded DNA genomes. The poxviruses are the largest of all animal viruses and visualized with light microscopy. By electron microscopy the poxviruses are brick- shaped or oval structures, measuring 200 to 400 nm. The nucleosome contains double-stranded DNA, which is surrounded by a membrane. The outer surface of the lipoprotein bilayer has surface tubules that are randomly arranged and give the virion its characteristic textured appearance. The lipid composition of the membrane is different from that of the host cell membrane. The nucleoprotein core, lateral bodies, and membrane are infectious as a unit, but the virus also often acquires an envelope  .
Poxviruses are among the most complex viruses known. Poxviruses have linear, double-stranded DNA genomes that are very variable from 130 to 230 kbp in different poxvirus species. As depicted in Figure 2, the two DNA strands are connected at their termini and form a continuous polynucleotide chain  . The hairpin termini exist in inverted and complementary forms that are incompletely base-paired and AT-rich .
Figure 1. The structure of VACV genomic DNA
The Classification of Poxvirus
The Poxviridae family is divided into two subfamilies, Chordopoxvirinae (poxviruses of vertebrates) and Entomopoxvirinae (poxviruses of insects), based on vertebrate and insect host range, respectively. The subfamily Chordopoxvirinae is further subdivided into ten genera, including Avipoxvirus, Capripoxvirus, Cervidpoxvirus, Crocodylidpoxvirus, Leporipoxvirus, Molluscipoxvirus, Orthopoxvirus, Parapoxvirus, Suipoxvirus and Yatapoxvirus. Here, we list the genera and main species of the Chordopoxviriae subfamily in the Table 1  .
Table 1. Genera and main species of the Chordopoxviriae subfamily
|Genus and Species
||Genus and Species
|Molluscum contagiosum virus
||Bovine papular stomatitis virus
|Lumpyskin disease virus
|Variola (smallpox) virus
||Humans, cattle, buffalo, swine, rabbits
||H are fibroma virus
||Squirrel fibroma virus
|Uasin Gishu disease virus
||Lumpy skin disease virus
||Cattle, Cape buffalo
See All Related Proteins of Poxvirus
What are Diseases Caused by Poxvirus?
Poxvirus infections typically result in the formation of lesions, skin nodules, or disseminated rash. As mentioned before, among of the ten genera, Orthipoxvirus, Parapoxvirus, Molluscipoxvirus, and Yatapoxvirus contain viruses that cause human infections. Smallpox and molluscum contagiosum are specifically human diseases. The genus Leporipoxvirus includes myxoma virus, which causes the fatal disease myxomatosis in European rabbits and was used successfully to control rabbit plagues. In this section, we focus on the Smallpox and molluscum contagiosum.
Smallpox is a contagious, disfiguring and often deadly disease caused by variola virus (also known as smallpox virus). It has affected humans for thousands of years. Naturally occurring smallpox was eliminated worldwide by 1980. Smallpox can be spread by humans only. Currently, there is no evidence that smallpox can be spread by insects or animals.
Before smallpox was eliminated, it was mainly spread by direct and fairly prolonged face-to-face contact between people. Moreover, smallpox can also spread through contact with contaminated clothing and bedding, although the risk of infection from these sources is less common. In rare instances, smallpox can spread via the air in enclosed settings, such as a building (airborne route).
The first symptoms of smallpox usually appear 10 to 14 days after you're infected. During the incubation period of 7 to 17 days, you look healthy and can't infect others. Following the incubation period, several flu-like signs and symptoms occurs, including fever, overall discomfort, headache and severe fatigue. A few days later, flat, red spots appear first on your face, hands and forearms, and later on your trunk.
So far, there is no cure or treatment for smallpox except for vaccine. A vaccine can prevent smallpox, but the risk of the vaccine's side effects is too high to justify routine vaccination for people at low risk of exposure to the smallpox virus. Once you have developed the smallpox rash, the vaccine will not protect you.
Molluscum contagiosum is a viral infection caused by a poxvirus (molluscum contagiosum virus). The result of the infection is usually a benign, mild skin disease characterized by round, firm, painless bumps ranging in size from a pinhead to a pencil eraser. If the bumps are scratched, the infection can spread to surrounding skin. Moreover, molluscum contagiosum also spreads via person-to-person contact and contact with infected objects. While it is most common in children, molluscum contagiosum can affect adults as well, especially those with weakened immune systems.
As molluscum contagiosum is self-limited in healthy individuals, treatment may be unnecessary. You can take some measure to help prevent the spread of the virus, such as keeping your hand clean, avoiding touching the bumps directly and rejecting to share personal items. If you have molluscum contagiosum on or near your genitals, don't have sex until the bumps are treated and have completely disappeared.
Related Protein Reagents
As mentioned before, variola virus (VARA) and vaccinia virus (VACV) are the most notable poxvirus around the world. CUSABIO provides a larger number of protein about VARA amd VACV. In this section, we list several proteins of VARA and VACV. Of course, besides the proteins shown on the follows, CUSABIO also provides proteins of genus of other poxviruses. If you are interested in them, you can contact us by the livechat.
 Buller RML, Palumbo GJ. Poxvirus pathogenesis [J]. Microbiol Rev. 1991, 55:80-122.
 Dayna G. Diven and Galveston, Texas. An overview of poxviruses [J]. J AM ACAD DERMATOL J ANUARY. 2001.
 Geshelin P and Berns KI. Characterization and localization of the naturally occurring cross-links in vaccinia virus DNA [J]. J Mol Biol. 1974, 88: 785–796.
 Baroudy BM, Moss B. Sequence homologies of diverse length tandem repetitions near ends of vaccinia virus genome suggest unequal crossing over [J]. Nucleic Acids Res. 1982, 10: 5673–5679.
 Bernard Moss. Poxvirus DNA Replication [J]. Cold Spring Harbor Perspectives in Bioligy. 2013.
 P.-P. Pastoret and A. Vanderplasschen. Poxviruses as vaccine vectors [J]. Comparative Immunology, Microbiology& Infectious Diseases. 2003, 26: 343–355.
 Fenner's Veterinary Virology. Book • 5th Edition. 2016.