Large and complex DNA virus.
Average incubation period is 10-12 days with a range of 7-17 days.
Manifests by an abrupt onset of malaise, fever, myalgias, headache and weakness for 2-3 days followed by an exanthema in the mouth and oropharynx and then a cutaneous rash which crusts at about 2 weeks.
Risk of maximum infectivity during the eruptive oral exanthema phase with continued risk of transmission of infection until the crusting stage ends.
The rash principally involves the face and extremities.
No proven antiviral therapy.
Two forms exist, variola major and variola minor with a mortality rate of 30% and 1%, respectively.
Neurological complications are uncommon.
Contains live vaccinia virus , a milder form of variola (smallpox) virus.
Does not contain smallpox vaccine and cannot cause the illness.
After a single vaccination 95% of patients are protected within 10 days, and immunity lasts at least 5 years.
All nations in the world have stopped vaccination.
Historically associated with a 30% case fatality.
Tecovirimat approved for smallpox and is based on studies of animal models using related orthopox viruses, specifically nonhuman primates to demonstrate efficacy.