Orthopoxvirus is a genus of viruses known to cause diseases in humans and animals. This group includes notable viruses such as smallpox and monkeypox. Orthopoxviruses are characterized by their large, complex structure and double-stranded DNA, which allows them to replicate efficiently within host cells. These viruses are typically transmitted through direct contact with infected individuals or contaminated materials. Symptoms can vary but often include fever, rash, and lesions on the skin. Vaccination has been effective in controlling some orthopoxvirus infections, particularly smallpox, which was declared eradicated in 1980.