Transmission of the Ebola virus occurs mostly within families, in hospitals and at funerals, not randomly like the flu, Yale scientists said Tuesday, and far fewer cases go unreported than has previously been estimated.

That implies, they said, that the epidemic is unlikely to reach the gloomy scenarios of hundreds of thousands of cases that studies released in September had forecast were possible; the most pessimistic one, from the Centers for Disease Control and Prevention, had predicted up to 1.4 million cases by late January.

As of Monday, there were 18,464 confirmed cases in Liberia, Sierra Leone and Guinea, with 6,841 deaths, according to the World Health Organization, far more than from all the previous Ebola outbreaks combined.

The new study, led by epidemiologists from the Yale School of Public Health, was published online by the journal Clinical Infectious Diseases. Scientists from Texas, Brazil and the Liberian Health Ministry contributed to the research.