Orthopoxvirus

A genus of viruses that includes the causative agents of smallpox and other diseases

Orthopoxvirus is a genus of viruses in the family Poxviridae, subfamily Chordopoxvirinae. This genus includes several species that are pathogenic to humans and animals, most notably the Variola virus, which causes smallpox. Other members of this genus include the Vaccinia virus, used in the smallpox vaccine, and the Monkeypox virus, which causes monkeypox.

Structure

Orthopoxviruses are large, brick-shaped viruses with a complex structure. They have a double-stranded DNA genome, which is linear and approximately 130-300 kilobase pairs in length. The viral particle is enveloped and contains a core that houses the DNA and associated proteins. The surface of the virus is covered with tubules and filaments, giving it a distinctive appearance under electron microscopy.

File:Orthopoxvirus virion.jpg

Electron micrograph of an Orthopoxvirus virion.

Replication

Orthopoxviruses replicate in the cytoplasm of the host cell, which is unusual for DNA viruses. The replication cycle begins with the attachment of the virus to the host cell surface, followed by entry and uncoating. The viral DNA is then transcribed by viral RNA polymerase, and the resulting mRNA is translated into viral proteins. The assembly of new virions occurs in cytoplasmic factories, and mature virions are released by cell lysis or budding.

Pathogenesis

Orthopoxviruses can cause a range of diseases in humans and animals. The most notorious is smallpox, caused by the Variola virus, which was eradicated in 1980 following a successful global vaccination campaign. Monkeypox, caused by the Monkeypox virus, is a zoonotic disease with symptoms similar to smallpox, though generally less severe. Other orthopoxviruses, such as the Cowpox virus, can also infect humans, typically causing localized skin lesions.

Epidemiology

The epidemiology of orthopoxvirus infections varies by species. Smallpox was historically a major human disease, but it no longer occurs naturally. Monkeypox is endemic in certain regions of Africa, with occasional outbreaks in other parts of the world. Cowpox is primarily a disease of rodents, but can be transmitted to humans through contact with infected animals.

Prevention and Control

Vaccination is the primary method of prevention for orthopoxvirus infections. The smallpox vaccine, which uses the Vaccinia virus, provides cross-protection against other orthopoxviruses. In the event of an outbreak, isolation of infected individuals and contact tracing are important measures to prevent spread.

Research and Development

Research on orthopoxviruses continues, particularly in the context of biodefense and emerging infectious diseases. The development of new vaccines and antiviral therapies is an active area of investigation. Understanding the molecular biology and pathogenesis of these viruses is crucial for developing effective countermeasures.

Related pages

• Smallpox
• Monkeypox
• Vaccinia
• Poxviridae