When swine flu emerged in Mexico last April, it was dubbed a “killer virus” because of its apparent high mortality rate. By mid-June the flu had spread to 73 other countries, infecting 30,000 people and prompting the World Health Organization to issue its highest warning, a Phase 6 pandemic alert. In the United States, concern took off in late August, when the President’s Council of Advisors on Science and Technology said the virus could infect up to 150 million Americans and kill 30,000 to 90,000. And then, on October 23, President Obama declared swine flu a national emergency, noting that “the potential exists for the pandemic to overburden health-care resources in some localities.”
The current strain of swine flu, formally known as the 2009 H1N1 flu, is a mutated cousin of the 1918 Spanish flu, which affected both humans and pigs. That virus took 50 million to 100 million lives worldwide, according to Jeffery Taubenberger, the pathologist who sequenced its entire genome.
Fears that this year’s virus would behave like its 1918 relative were heightened when two characteristics of the new flu were noted as similar to the earlier pandemic. First, cases of swine flu broke out before the usual flu season; and second, a disproportionate number of young people were reported to be sickened by it.
By September five pharmaceutical companies had promised to produce 250 million doses of 2009 H1N1 vaccines, and experts assured the public that these inoculations were safe. But as of the first week of November, only 26 million doses had been distributed to hospitals and doctors’ offices.
Nancy Cox, head of the flu division at the Centers for Disease Control and Prevention (CDC), says that her group is preparing for the worst. “In certain situations such as 1918, there was a rather mild spring season of disease followed by a much more severe fall wave,” she says. “There’s a seasonality component that caused the virus to spread more rapidly and more deeply into the population.”
An estimated 22 million American citizens were infected with the new H1N1 virus in the months before Obama declared the national emergency, according to the CDC, and about 4,000 of those people died. Each year seasonal flu kills approximately 35,000 people in the United States alone. Without extensive immunization, the H1N1 flu is on track to surpass that toll, says Dean Blumberg, associate professor of pediatric infectious disease at the University of California at Davis Children’s Hospital. Because this virus is so novel, few people are protected by preexisting immunity. “Pretty much everyone is going to get it,” Blumberg says, “so we’re expecting more deaths and complications.”