These sequences by themselves are harmless: They are strings of information. As Garcia Sastre puts it, “There's no smoking gun in the 1918 sequences. So we really want to find out what made it kill, so that if it emerges again in the future, we'd be able to recognize a virus with virulence characteristics like 1918.” Through a technique Garcia Sastre and colleagues developed, these sequences― symbols on paper―can be translated into actual viral RNA. Since the whole genome hasn't yet been published, scientists can't recreate the entire 1918 flu. But they can combine some 1918 genes either with laboratory strains that have been adapted to grow, in mice, which don't normally catch human flu, or with ordinary human flu strains to yield new artificial strains. Then the researcher infects mice with his new strain. Strains using three of the 1918 genes are already known to kill mice. These techniques are fascinating. But the work is also dangerous. Peter B. Jahrling, chief scientist at the National Institute of Allergy and Infectious Diseases, compares the research to “looking for a gas leak with a lighted match.” What concerns Jahrling and Brown, among others, is that experiments involving 1918 genes are not being carried out under the highest biosafety level, BSL-4. While most of the scientists use what is known as BSL-3 plus, or enhanced conditions, they do not use space suits, chemical showers or gas-tight cabinets in their work. Still, it's hard to say how much difference a higher biosafety level would make: Work on dangerous agents is, by definition, dangerous. Even in BSL-4 labs mistakes can happen, and some of these mistakes have been fatal―to the experimenter. In addition to three laboratory escapes of the SARS virus in 2003 and several resultant fatalities, a number of Russian researchers at the Vektor laboratories in Siberia have died of Ebola, and several scientists at Boston University contracted tularemia, or rabbit fever, in recent years. The 1918 flu is a particularly potent agent, and it isn't only the lives of experimenters at risk if one of them contracts one of the artificial constructs. As Brown puts it, “These are tried and true virulence strains for humans. This virus and its genes have to be given a bit more respect. You don't want it out in nature where it could cause serious disease.” While the antiviral drug oseltamivir, or Tamiflu, seems to protect against the 1918 constructs, Jahrling says “you'd really want a belt to go with those suspenders.” And Richard Ebright, a microbiologist at Rutgers University, says that “using Tamiflu as a prophylactic makes it more likely that if a strain is accidentally released, it's going to be a Tamiflu-resistant strain.” There's an added danger. The scientists now known to be working on these strains are all respected by their peers; no one expects them to be careless. But the five published sequences are in the public domain, and there is simply no way to know who else may be working on them at any given time. Even more disturbing is what may happen when Taubenberger publishes the remaining three gene sequences. Then the entire 1918 flu could be built from scratch by anyone, anywhere, who has sufficient resources and skill. It is quite conceivable that resurrected 1918 flu could someday be used as a bioterrorist agent. Clearly, if these genes had never been dug up, we wouldn't have to worry about any of this. And how necessary is this admittedly remarkable work in the first place? Evolutionary biologist Paul Ewald of the University of Louisville points out that influenza is normally a relatively mild disease: It keeps its hosts up and moving in order for it to spread. But the precise conditions of the Western Front allowed the virus to evolve unprecedented virulence. Without those conditions, lethal pandemic flu cannot evolve. Says Byerly, “The 1918 flu epidemic most likely will not happen again because we won't construct the Western Front again.” If Ewald and Byerly are right, then the principal rationale for this research―protection from another lethal pandemic―blows away, though the research remains a useful tool to show how lethal flu kills. Indeed, if they are right, the greatest danger of lethal pandemic flu may lie in some slip, some failure of lab protocol or Tamiflu, or even in someone's malice. Then the vaunted cure may prove worse than the disease.