On April 25, Rod Daniels, the deputy director of the World Influenza Centre in London, was at a meeting in Germany when he received a call from a co-worker: an influenza outbreak had been reported in Mexico and the first samples of the virus were on their way to London for examination. A virologist who has studied flu for more than 30 years, Daniels knew exactly what he was looking for. Influenza A viruses the type that can cause pandemics use a protein called hemagglutinin to bind to the cells of their animal hosts. When a virus jumps from animals to humans, its contagiousness is largely determined by what is called the "binding specificity" of this protein. An alpha-2,3 binding specificity means the virus is well suited to the cells in an animal respiratory tract but probably not human cells. An alpha-2,6 binding specificity, on the other hand, means the virus can easily bind to human cells.
"I got back to the lab, and as soon as we saw a sequence of the hemagglutinin, we looked at the receptor binding site and found indications of an alpha-2,6 binding specificity," Daniels, 54, recalls. "I knew then we have a problem."
Three months later, and the human race is entrenched in a battle with the H1N1 2009 pandemic virus, with infections reported in 168 countries. In this mortal contest, it's the job of Daniels and his fellow virologists to decode the opponent's playbook. Working in a grim, 1930s building in London's northern suburbs (its exterior was used to portray an insane asylum in the blockbuster Batman Begins), scientists at the World Influenza Centre receive virus samples from around the world and use sophisticated machinery to map their genetic structures. During normal years, the scientists concoct the recipe that the World Health Organization (WHO) uses for seasonal-flu vaccines. But in a pandemic year, they become sentinels looking for any changes in the virus that could alter the course of the pandemic.
"Right now this pandemic would appear to be a mild one," says the center's director, Alan Hay, 65. "But influenza viruses can change quite suddenly. And there's no reason another, more dangerous virus couldn't emerge with pandemic potential. It's crucial that we keep our eye on the ball."
Flu's hardiness as a human scourge is the result, paradoxically, of the instability of its genetic structure. One flu virus can easily swap genetic information with another or mutate as it reproduces. The World Influenza Centre is one of five WHO centers (there are others in Atlanta, Tokyo and Melbourne, and there's a lab in Memphis specializing in animal influenza) that form the hub of a global influenza-surveillance network. The center receives samples taken from ill patients in more than 100 countries. By examining the genetic makeup of the viruses in these samples, scientists can make educated guesses about how lethal and contagious a pandemic will be. But they are only guesses. While exhaustive, 21st century virology can explain and illustrate what's already happened and help health officials react the only valid, real-time laboratory is the human population itself.
"If we get reports of a more severe infection with higher mortality rates, we can map the changes that made the virus more severe and monitor its spread. That could help health officials formulate policies," says Hay. "But we are always playing catch-up with flu. It's impossible to stay ahead of this virus."