Four factors explain monkeypox’s decline, experts said. First, vaccines helped slow the virus’s spread (despite a rocky rollout). Second, gay and bisexual men reduced activities, such as sex with multiple partners, that spread the virus more quickly.

The third reason is related: the Pride Month effect. Monkeypox began to spread more widely around June, when much of the world celebrated L.G.B.T.Q. Pride. Beyond the parades and rallies, some parties and other festivities involved casual sex. As the celebrations dwindled, so did the increased potential for monkeypox to spread.