Our microB blog!: POXVIRIDAE

Structure of the Poxviridae:

http://www.microbiologybytes.com/introduction/structure.html

Genome
- Large double stranded DNA about 130-300 kbp in size.
- Linear genome.
- Noninfectious
- The ends of the genome form direct repeats known as inverted terminal repeats (ITRs).
- The important genes can be found in the central part of the genome whereas the non-essential genes are located at the ends of the genome.

Large DNA viruses
- About 200-400 nm long.
- The particles are very complex and covered with filamentous protein components that contain more than 100 proteins.
- Two morphological types of particles:
(i) Oval with criss-cross surface bonding
(ii) Brick-shaped
d. The whole particle is enclosed with envelope from host cell membrane.

Poxviruses have a complex structure.
- It can induce the specific and cross reacting antibodies.
- That is why it has the ability to vaccinate against one disease with other virus.

Poxviridae has two sub families: Chordopoxvirinae and Entomoxvirinae.
Chordopoxvirinae: Poxviruses of vertebrates.
Entomoxvirinae: Poxviruses of invertebrates more specifically insects.

Poxviruses that can infect humans can be found under the chordopoxvirinae sub family and most viruses can be found from the orthopoxvirus and the parapoxvirus genus.
Poxviruses are usually transmitted through direct contact.
Other poxviruses:

1. Vaccinia

Vaccinia belongs to the Orthopoxvirus genus is used as a vaccine against the smallpox virus. Since the vaccinia vaccine virus does not contain the smallpox virus, it cannot cause any smallpox infection. This virus cannot be transmitted through air (hence you cannot get infected by being in the same room as the infected person) but a person can be infected if the person has direct contact with the vaccination site. Some of the symptoms include rash, fever, headache and body ache.

From left:
http://upload.wikimedia.org/wikipedia/commons/8/8c/Vaccinia_virus_PHIL_2143_lores.jpg
http://www.bt.cdc.gov/training/Smallpoxvaccine/reactions/gen_vac_clinical.html

2. Smallpox virus

Smallpox, a member of the Orthopoxvirus is a severe, contagious disease that is caused by the variola virus. This virus believed to be originated in India or Egypt and it was the most fatal disease during 3000 years ago as there was no cure for the virus even though a major population of the people was infected with it. Smallpox can be spread through direct contact with contaminated things like clothing. The initial symptoms are high fever, headaches and body aches before progressing to rash.

http://www.viewzone.com/smallpox.html

3. Orf virus

It is a virus that belongs to the parapoxvirus genus. This orf virus causes infection to sheep and goats and sometimes the virus can infect to people that handle the sheep and goats. This is because the virus can establish infection where the skin is damaged. Painful lesions were seen first before it increases in size over a period of 4 weeks. Then the lesion will crust before it dries up after 6 to 8 weeks and fall off leaving with no scars.