“There’s a great deal of interest in a technology that can screen large numbers of people from a finger prick in only a few minutes,” said Cary Gunn, chief executive of Genalyte, a company in San Diego that says its approach can do just that. “You can imagine testing an entire planeload of passengers and screening through them cost-effectively.”

The World Health Organization is encouraging development of rapid tests, as is the federal government. The Food and Drug Administration is giving emergency authorization for use of qualified Ebola tests. On Oct. 25, it gave such a clearance for a one-hour test developed by BioFire Defense, although that test requires more than a few drops of blood and is typically sent to a laboratory. “It would have taken years to get this product approved through the traditional process,” said Kirk Ririe, chief executive of the company, which is based Salt Lake City and owned by the French diagnostics firm BioMérieux.

Companies are hoping to get their tests into the field in Africa in the next few months, but it is not clear how many will be in time to make a difference in the outbreak. And some health specialists caution that while one company after another is announcing an Ebola test, there is little information about their accuracy.

“It’s a wild, wild West a little bit in development,” said Dr. Mark Perkins, chief scientific officer of FIND, or the Foundation for Innovative New Diagnostics, a nonprofit organization working with the World Health Organization to assess Ebola tests. “Eight Ebola products on the market with no one knowing how they work is not helpful.”