In 1918, the flu killed 20 million people. A comprehensive study helps explain what made it so deadly.
History's meanest flu. I'm Bob Hirshon and this is Science Update.
In 1918, a flu epidemic killed twenty million people. Now, scientists have found one reason why.
Working with preserved samples of the 1918 virus, University of Wisconsin virologist Yoshihiro Kawaoka and his colleagues have identified a single gene that made it much nastier. He says mice that shrugged off ordinary flu viruses reacted very differently to a virus with the 1918 gene.
They died, and also the lung of the mouse infected with the virus that contained 1918 gene showed extensive hemorrhage.
Besides shedding light on a medical mystery, the study will help doctors understand how today's flu viruses work. I'm Bob Hirshon for AAAS, the Science Society.
Making Sense of the Research
There are many reasons why the flu epidemic of 1918 was so harsh. There were no vaccines at the time, so the flu spread easily. Sanitation was also much more of a problem at the time, and without modern antibiotics, doctors were less equipped to treat secondary infections that arose in flu patients.
Still, all of this was true in 1917, 1919, and many other years of the time, but the 1918 flu season stands out because of the virus involved. It's long been known that the 1918 flu virus was more powerful than most viruses today, but we didn't know exactly why.
Kawaoka's study helps to answer this question by narrowing the virus' power down to a single gene. His team looked for genes that differed in the 1918 virus and a sample virus from today, and tried switching them around. They found that one particular gene from the 1918 sample changed an ordinary modern virus into an efficient killer.
The gene in question codes for a protein called hemaglutanin, which the virus uses to attach to the cells of its victim. Somehow, the 1918 version of hemaglutanin seems to help the virus infect cells much more easily. It's not clear exactly how this happens; that's what Kawaoka and his colleagues would like to find out next.
Although this experiment may sound like an easy target for exploitation by terrorists, Dr. Kawaoka says that engineering a virus is a lot harder than it sounds. Besides, he points out that there are viruses in the human population today (for example, the avian flu virus in Asia) that are just as infectious. And hopefully, if a virus like the 1918 flu ever hit today's population, we would be better equipped to treat it—even with our shortage of flu shots.
Now try and answer these questions:
- Why are scientists interested in the 1918 flu epidemic?
- What specifically did Kawaoka's experiment determine?
- What other factors made the 1918 flu so deadly?
- Suppose Kawaoka found that the 1918 flu was no deadlier than a typical modern flu virus. What would you conclude?