(JNS) — Conspiracy theories cast a shadow over the 75th World Health Assembly, the decision-making body of the World Health Organization (WHO), as hundreds of health officials and diplomats converged on Geneva last week. One of the assembly’s key goals—to draft a new agreement that would “strengthen pandemic prevention, preparedness and response”—opened the U.N.-affiliated world body to accusations that it was attempting to usurp national governments’ powers to make health decisions.

The conspiracy caught fire online as cultural, media and political figures, such as British co...