Put that all together and how badly will Covid-19 strike poor countries?

“We just don’t know,” Esther Duflo, an M.I.T. economist who won the Nobel in economic science last year, told me.

Dr. David Nabarro, a veteran U.N. global health expert, put it this way: “We can only have hypotheses, and the hypotheses are vaguely hopeful.”

I share that view: As a purely medical matter, I’m not as pessimistic about the impact on the developing world as some other commentators are. But I greatly fear that the indirect impact will be devastating.

Polio eradication campaigns are being suspended. The same is true of vitamin A distribution, which saves children’s lives and prevents blindness. School feeding programs have often been shut down along with schools.

In Bangladesh, where the economy has been hard hit by the coronavirus, a survey by a respected aid group, Brac, found that household incomes have declined an average of 75 percent. Factory workers saw incomes drop by 79 percent, drivers by 80 percent, city day laborers by 82 percent, maids by 68 percent and rickshaw pullers by 78 percent. Four in 10 respondents had three days’ worth of food at home or less.

Schools are closed in many countries, and some students, especially girls, will probably never return to their studies. When families are desperately short of money and food, they are less likely to pay school fees, particularly for girls. They also cope by marrying off their daughters, even young ones, so that another household has the responsibility of feeding them.