Inside special isolation units at an Atlanta hospital on Wednesday, Kent Brantly and Nancy Writebol, the two Americans infected with Ebola in West Africa, appeared to be responding to an experimental medicine devised by an obscure biotechnology company with ties to the Defense Department.

In West Africa, the estimated death toll from the outbreak kept rising, to 932, by the latest official count.

How and why Dr. Brantly and Ms. Writebol received the drug, ZMapp, is one of the many mysteries surrounding what has been called a “secret serum,” including the big one: Does it really work? The Americans are the only two patients who have been treated with the medicine, out of perhaps thousands who might have benefited so far, raising old questions about who does — and does not — have access to medications, including experimental drugs.

But the San Diego-based Mapp Biopharmaceutical, the primary developer of the drug, was consumed Wednesday with how to manufacture more of it with an eye to providing the drug to more patients, probably in the form of clinical trials.