Spanish influenza of 1918: Decoding clues long left behind

Images from the 1918 Spanish influenza have never been far from the minds' eyes of scientists and infectious disease experts.

In that year, this especially virulent flu strain claimed 10 million to 50 million lives worldwide, including 675,000 in the United States.

Fast forward to now.

A team of researchers from the Centers for Disease Control and Prevention, the Armed Forces Institute of Pathology, Mount Sinai School of Medicine and the Dept. of Agriculture collaborated to resurrect this deadly strain by using gene sequences from an infected person's preserved tissue. Their goal was to find clues to help prepare for, and perhaps even prevent, a repeat of that historic calamity. The findings were detailed in the Oct. 7 issue of Science and the Oct. 6 issue of Nature.

Over the decades, experts have maintained that another pandemic will eventually occur. For now, close watch continues on the H5N1 avian flu strain which began in Asia in 2003 and continues to circulate. So far this virus has not easily passed from birds to humans or from person to person. But flu viruses are infamous for their ability to change.

In this regard, the insights resulting from looking back are already offering important applications in the here and now. For instance, researchers pinpointed markers to help scientists focus on detecting changes in the evolving H5N1 virus that might make widespread transmission among humans more likely. This led to the finding that the H5N1 strain has acquired five of the 10 gene sequence changes associated with human-to-human transmission in the 1918 virus.

The researchers also determined in the test tube and in mice which genes are most likely to account for the lethal effects of the 1918 virus.

"By identifying the characteristics that made the 1918 influenza virus so harmful, we have information that will help us develop new vaccines and treatments," said Terrence Tumpey, a CDC senior microbiologist. "Influenza viruses are constantly evolving, and that means our science needs to evolve if we want to protect as many people as possible from pandemic influenza."