But the novel coronavirus is an opportunist. It looks for densely packed, unprotected populations. Spreading via aerosols from one person to the next, it sets up a proverbial laboratory in each body it infects. Every individual SARS-CoV-2 infection mutates every two weeks for as long as it’s active, looking for evolutionary pathways that might produce a new increasingly transmissible variant. New variants help the virus spread even faster in a self-reinforcing cycle that ends only when strong social-distancing mandates, vaccinations, the antibodies of survivors—or, more likely, a combination of all three—cut off its transmission pathways. The harder it is to socially-distance, and the lower the vaccine uptake, the longer the pathogen has to run amok... Nigeria, with its teeming cities, deep poverty and ramshackle health system is, from an epidemiological standpoint, a lot like India—except worse, in some aspects. Where India at least has some domestic vaccine-manufacturers, Nigeria has none. It must import all of its doses. That helps to explain why the country has partially vaccinated just 1 percent of its population—and fully vaccinated almost no one. The government in Lagos expects to receive 84 million vaccine doses from AstraZeneca and Johnson & Johnson in coming weeks.