Deaths in early 1918 heralded flu pandemic.

An examination of New York City death records from early last century suggests that the world's deadliest flu virus was on the loose in New York several months before it exploded into the 1918-1919 global pandemic.

At the time, that foreknowledge wouldn't have averted the catastrophe that killed at least 40 million people worldwide, says Donald R. Olson of Columbia University. But nowadays, he adds, a "herald wave" of flu could provide crucial warning of an impending pandemic. "It would give us 6 to 7 months to produce and distribute vaccine," he says.

Olson and his colleagues calculated monthly death rates in all age groups in New York from 1911 to 1921 and found an unusual spike among young adults between February and April 1918. That group was hardest hit by the pandemic, which flu historians have argued began in Kansas and spread to New York and elsewhere in the fall of 1918. The number of deaths in each age group in the city in early 1918 was proportional to how heavily each group was affected by the pandemic, which began revving to full strength in New York in September.

The increased death rates in early 1918 must have resulted from an early and previously unrecognized wave of the pandemic, Olson's team proposes in the Aug. 2 Proceedings of the National Academy of Sciences.

With a virus that could cause the next flu pandemic now infecting birds across Asia, the U.S. government decided last week to spend $100 million to stockpile an experimental flu vaccine.--B.H.