The potentially fatal virus, a relative of the eradicated smallpox and harmless cowpox, is endemic to central and western Africa. A large proportion of the roughly 100 cases in the latest outbreak have been among gay or bisexual men.

The potentially fatal virus, a relative of the eradicated smallpox and harmless cowpox, is endemic to central and western Africa. A large proportion of the roughly 100 cases in the latest outbreak have been among gay or bisexual men.