Severe, hard-to-control blazes in densely populated areas like Los Angeles drove the year’s record losses.

Severe, hard-to-control blazes in densely populated areas like Los Angeles drove the year’s record losses.

© Loren Elliott for The New York Times

The babies were part of a vaccine trial for a respiratory virus in the 1960s and died shortly after. Their families said they had been unaware of the trial until recently.

The types of Ebola and hantavirus worrying officials are very different from the species identified decades ago, raising new questions about how to respond.