Mutation Identified That Would Likely Increase Transmissibility of H1N1 Influenza

In the fall of 1917, a new strain of influenza swirled around the globe. At first, it resembled a typical flu epidemic: Most deaths occurred among the elderly, while younger people recovered quickly. However, in the summer of 1918, a deadlier version of the same virus began spreading, with disastrous consequence. In total, the pandemic killed at least 50 million people — about 3 percent of the world’s population at the time. That two-wave pattern is typical of pandemic flu viruses, which is why many scientists worry that the 2009 H1N1 (“swine”) flu virus might evolve into a deadlier form. H1N1, first reported in March 2009 in Mexico, contains a mix of human, swine, and avian flu genes, which prompted fears that it could prove deadlier than typical seasonal flu viruses. However, the death toll was much lower than initially feared, in large part because the virus turned out to be relatively inefficient at spreading from person to person. In a new study from MIT, researchers have identified a single mutation in the H1N1 genetic makeup that would likely allow it to be much more easily transmitted between people. The finding, reported on March 2, 2011 in the journal PLoS ONE, should give the World Health Organization, which tracks influenza evolution, something to watch out for, said Dr. Ram Sasisekharan, senior author of the paper.“There is a constant need to monitor the evolution of these viruses,” said Dr. Sasisekharan, the Edward Hood Taplin Professor and director of the Harvard-MIT Division of Health Sciences and Technology. Some new H1N1 strains have already emerged, and the key question, Dr. Sasisekharan added, is whether those strains will have greater ability to infect humans.