Until several months ago, demographers regarded a youthful age structure as an unequivocally detrimental demographic characteristic. Where more than half of the population is younger than age 25, countries are unable to attain high levels of economic and human capital development and face an increased risk of some forms of civil conflict. Yet, so far, during the ongoing pre-vaccine stage of the COVID-19 pandemic, the most age-structurally mature countries have been hardest hit by the disease. These countries are generally urbanized, wealthy, well-educated, and include a large proportion of seniors. And, somewhat surprisingly—despite being equipped with advanced medical technologies—these countries are experiencing the highest rates of mortality from complications related to COVID-19.

Late last year, what is thought to be a bat-associated coronavirus infected humans in Wuhan, a city of 11 million in China, possibly after a stopover in illegally traded pangolins—setting off a global pandemic. This kind of thing has happened before—with AIDS, SARS, and MERS, for example. Much remains unknown about the biology of COVID-19, which is alarmingly communicable by people with few or no symptoms. But an epidemic is only part biology. It is also driven by cultural factors, and urbanization is a crucial aspect. As sites of large gatherings and dense living conditions, cities offer the perfect settings for the spread of infection, yet their role seems to have often gone unremarked in discussions of the pandemic.

In Kenya, primary and secondary school students take courses called Life Skills Education. So do students in Malawi, Mozambique, Namibia, and Swaziland. South Sudan adds “peace-building” to the subject title. Lesotho, Madagascar, Rwanda, Tanzania, Uganda, and Zambia are more direct. These countries add the word “sexuality” to the course name.

The Western Sahel region—a cluster of arid, low-income countries stretching from Senegal, on Africa’s Atlantic coast, inland to Mauritania, Burkina Faso, Mali, Niger, and Chad—is home to the world’s most youthful populations. According to current UN Population Division estimates, about 57 percent of this six-country region’s population is 19 years old or younger. As security conditions deteriorate across the rural Sahel, governments in Europe and North Africa are taking notice of these countries’ demographic status—and for good reasons. Sustained population youthfulness (often called a “youth bulge”) contributes to low levels of educational attainment, joblessness and social immobility, and ultimately to rapid population growth, which tends to drive declines in per-capita availability of freshwater and other critical natural resources: factors that are associated with the risk of persistent violent conflict and represent powerful push factors for migration.