“The numbers are decreasing, but we don’t know why,” said Malin Lager, a spokeswoman at a Doctors Without Borders treatment center just outside Monrovia, the capital. Its vast campus of white tents, which has a capacity for 253 patients, had only 90 on Sunday.

“It’s too early to celebrate,” Ms. Lager said…

There is also the likelihood that many people dying of Ebola in Liberia are hidden from the authorities, as has been true throughout the epidemic.

Many parts of the country are not well monitored, many contacts of Ebola patients are not traced, and officials have long acknowledged that the statistics on the numbers of Ebola cases across West Africa are rough estimates, at best.