ON TUESDAY EVENING, OCTOBER 22, THE PHONE rang. It was a federal official I have known for years. "The U.S. government can't sit on this much longer," he told me. His normally calm voice was cracking. "Three people down in Florida have a rash; 30 are in quarantine. The CDC is all over it." He would not say the word we both were thinking: smallpox. "I can't stay on the phone; turn on the news," he said.
I thought it was the end of the world. By the end of next year, the U.S. government probably will have grown enough cell-culture smallpox vaccine to immunize everyone in the country. In four or five years, testing of new antiviral drugs presumably will have progressed, giving us a good idea of whether post-infection treatment of smallpox will actually work. But right now? What can we do right now? Not a lot.
The Florida rashes were a false alarm. By the next morning, four doctors had diagnosed shingles in the afflicted patients, who with their contacts were released from quarantine. Smallpox had slipped back again from appalling certainty to specter--a "low-risk, high-consequence threat," as experts like to put it.
But that has new meaning nowadays. A few months ago, the CDC wouldn't have dreamed of slapping three people with shingles into quarantine together with their friends and relations. How serious is the smallpox threat? There is no unambiguous answer. What we know is this:
Smallpox, unlike the ubiquitous anthrax, would be hard for terrorists to obtain, but not impossible. Since 1980, when the disease was declared eradicated, the only legal stocks of the smallpox virus have been held in two repositories, the Centers for Disease Control in Atlanta, Georgia, and the Vector Research Center in Koltsovo, Siberia. But American intelligence reports indicate that the virus is also in the hands of the North Korean bioweapons program, as well as the secret Russian military laboratory at Sergiyev Posad. And that's just for starters. Most experts believe that the Iraqis also possess the virus--not least because Iraqi soldiers captured during the Gulf War showed evidence of having been recently vaccinated for smallpox, and this was 10 years after the disease was supposed to have disappeared from the earth. Though with less certainty, the experts also suspect Iran, China, India, Syria, and Israel of having illicit stocks of the virus. In the circumstances, we cannot be confident that stocks of smallpox could not fall into terrorist hands.
The common claim is that a smallpox attack, if it were to happen, would kill about one infected person in three. But it is actually quite difficult to calculate the damage a smallpox outbreak would cause--especially if the disease were seeded in many locations at once, the most dangerous scenario.
In part this is because smallpox strains--even variola major, the form responsible for most infections throughout human history--vary quite a lot in their virulence. Experts say that variola-major strains from Africa typically killed about 10 percent of those infected, while the much hotter strains from India and Bangladesh, where crowded circumstances permitted the easy passage of extremely lethal strains from one person to another, killed up to half of those infected. Furthermore, some people, regardless of the strain involved, just get much sicker than others do. Pregnant women, for instance, and persons with compromised immunity are more likely than others are to develop hemorrhagic smallpox, a severe and almost always fatal form of the disease. According to Ken Alibek, former first deputy director of the Soviet bioweapons program, Russian scientists weaponized India-67, an extremely lethal smallpox strain, years ago. But the truth is that we have no idea what strain a bioterrorist might use.
Several factors suggest that the death rate from a smallpox attack in the United States could be much lower than is usually projected. For instance, the American public, and indeed the rest of the world, while certainly lacking total immunity, is far from a virgin-soil population. …