Since the novel coronavirus began its global spread, influenza cases reported to the World Health Organization have dropped to minuscule levels. The reason, epidemiologists think, is that the public health measures taken to keep the coronavirus from spreading also stop the flu. “There’s just no flu circulating,” says Greg Poland, who has studied the disease at the Mayo Clinic for decades. For now, future flu transmission remains a roll of the dice. Influenza Cases Worldwide, by RegionThe World Health Organization tracks influenza transmission in 18 zones.