Defensive Line

Chasing the evolution of influenza has kept Centers for Disease Control and Prevention virologist Nancy Cox on the run for 31 years.

Nancy Cox wants to stop playing defense. As a virologist at the Centers for Disease Control and Prevention since 1975, she has spent her entire career chasing a nimble and stealthy opponent that has always been at least one step ahead: the rapidly mutating influenza virus.

Not that Cox is complaining. The fast pace of influenza's evolution, the hefty toll it takes each year, and the constant potential for a global pandemic were reasons why she chose to study the virus in the first place. "I find the organism fascinating because of its ability to change and replicate in multiple different forms," she says. "I haven't gotten tired of influenza because there's always something new."

Cox first battled the virus as a 9-year-old in Iowa in 1957, when the Asian flu pandemic killed millions. She beat the bug, and went on to study it at Cambridge University. During a fellowship at CDC, she saw firsthand the complex interplay between science and public policy when the United States confronted outbreaks of swine flu and Legionnaire's disease and had to decide whether to provide vaccinations. Instead of returning to academia as she had planned, she chose to stay at CDC. "I could get up every morning and know that what I was doing was important," she says.

Now, as head of CDC's influenza division, Cox has assembled a team of cutting-edge scientists whose aim is to take the offensive. "We're always chasing the evolution of the virus, and what we'd really like to do is get ahead of the curve," she says. By using genetic data and patterns of evolution, they hope to be able to anticipate influenza's next move-predicting which strains are likely to outsmart antibodies and which could defy vaccines.

One group of viruses is of particular interest. Called H5N1, it lives mainly in birds. Since 2003, though, H5N1 viruses have attacked more than 200 people in 10 countries. If they were to mutate into a form that could pass easily from human to human, the effect would be devastating. "Obviously, we're very, very concerned," says Jacqueline Katz, chief of the immunology and pathogenesis branch under Cox. "We all believe it is a potential pandemic threat."

Cox, who also directs the World Health Organization collaborating center for influenza, has been preparing for that possibility on multiple fronts. She and her group have been monitoring the avian viruses circulating in Asia. They have developed a nasal swab test for diagnosing human and avian influenza infections and identified potential vaccines for H5N1. They re-created the virus that killed 40 million people in 1918 to study what made it so dangerous and combined H5N1 with a highly contagious human strain in a secure lab to better understand its potential.

Cox "is widely known as a giant international authority in the field," says Keiji Fukuda, acting coordinator of WHO's Global Influenza Program. "There is no one today who has her combined breadth and depth of knowledge about influenza." That's why she's frequently called on to consult with foreign governments. This past year, for example, she was the lone American on an international team of experts that traveled to China, where there were suspected cases of avian influenza. The team reviewed the data and the safety precautions the Chinese had put in place. "It was very gratifying to see the enormous progress they had made and the fact that they were able to very carefully and accurately diagnose these cases of bird flu," says Cox, who has been working with the Chinese authorities since the late 1980s.

But while avian flu makes headlines, it's only one part of her job; seasonal influenza kills thousands of Americans each year. Cox helps update the vaccines twice a year, and her innovations in this area have saved countless lives. And despite the fact that Cox works on high-level health policy and management issues, "she's still very much in touch with the science that goes on," Katz says. "She always sheds light on an issue other people may not consider."

Cox's greatest accomplishment, according to both Katz and Fukuda, has been building the CDC influenza team, which Fukuda calls "the strongest combined laboratory and epidemiology influenza program in the world." That achievement helped pave the way for the decision earlier this year to elevate the influenza group from a branch to a division. "My goal," says Cox, "is that when I retire, they will carry on and not miss a beat."