Dar es Salaam — Tanzanian President John Magufuli, Africa's most prominent Covid-19 denier, disappeared from public sight 17 days ago. Now, he is widely rumored to be seriously ill with the same virus that he has dismissed and downplayed over the past year. Last May, Magufuli declared that "Tanzania has beaten coronavirus" after ordering three days of national prayer. The president abruptly stopped updating the number of cases, and assured foreign tourists that Tanzania's game parks and Indian Ocean resorts were open for business, leading to a wave of travel advisories cautioning travelers to avoid the country. Since then, he...