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The detection of a new, fast-spreading strain of the virus in a remote mining town in eastern Congo led the World Health Organization to declare mpox a global public health emergency in August. Since then, its spread has only accelerated.

The virus is taking hold in crowded camps home to millions of displaced Congolese, who live crammed into rough shelters with limited access to water. And it has reached Congo’s cities, including its enormous, congested capital.

Belated efforts to control mpox in Kinshasa — by isolating patients and vaccinating their contacts — have been halting and haphazard, far outpaced by the speed of the virus’s spread and change.