FREETOWN, Sierra Leone — It seemed as if the Ebola crisis was abating.

New cases were plummeting. The president lifted travel restrictions, and schools were to reopen. A local politician announced on the radio that two 21-day incubation cycles had passed with no new infections in his Freetown neighborhood. The country, many health officials said, was “on the road to zero.”

Then Ebola washed in from the sea.

Sick fishermen came ashore in early February to the packed wharf-side slums that surround the country’s fanciest hotels, which were filled with public health workers. Volunteers fanned out to contain the outbreak, but the virus jumped quarantine lines and cascaded into the countryside, bringing dozens of new infections and deaths.

“We worked so hard,” said Emmanuel Conteh, an Ebola response coordinator in a rural district. “It is a shame to all of us.”

Public health experts preparing for an international conference on Ebola on Tuesday seem to have no doubt that the disease can be vanquished in the West African countries ravaged by it in the last year. But the steep downward trajectory of new cases late last year and into January did not lead to the end of the epidemic.