In 1979, anthrax was accidentally released in the city of Sverdlovsk (pop. 1,200,000) in the former Soviet Union, infecting about 80 to 100 people and killing at least 70. Russian officials claimed at the time that tainted meat sold on the black market was responsible; American officials argued that a nearby biological weapons facility released the killer spores. In the early 1990s, Harvard researchers visited the city to piece together the epidemiology of the outbreak. Their investigation, published in Science magazine in 1994, concluded that the Soviet cover story was false.

Now, physicist Dean A. Wilkening, director of the science program at Stanford's Center for International Security and Cooperation (CISAC), has revisited this Cold War tragedy and used its real-world data to improve our ability to model the medical effects of inhalational anthrax. This, in turn, allows him to model more accurately hypothetical scenarios such as the release of a kilogram of aerosolized anthrax in Washington, D.C., today.

The models researchers have used in such thought experiments "predict very different outcomes," says Wilkening, whose work to better understand the human effects of inhalational anthrax was supported by grants from the John D. and Catherine T. MacArthur Foundation and the Carnegie Corporation. Using real-world data from the Sverdlovsk outbreak and from limited nonhuman primate experiments, he was able to eliminate two of four theoretical models currently used in "what if?" scenarios that inform bioterrorism policies ranging from how much medicine we should have on hand in the Strategic National Stockpile to how rigorous post-attack decontamination efforts need to be. He reports his findings in the May 1 issue of Proceedings of the National Academy of Sciences.

"To date, researchers haven't paid enough attention to which model they use," Wilkening says. "Different models can give predictions that vary by a factor of 10 or more, so it matters which model one uses for predicting the human effects of inhalational anthrax." Wilkening aims to anchor models on the best available data and provide realistic models that the bioterrorism community can employ in policy studies.

The Sverdlovsk outbreak is "a sort of natural experiment," he says. "It's a tragic incident, but it also is a very valuable source of scientific data that one can use to distinguish between the four models currently in use." The upshot of his analysis is that two of the models currently in use are not accurate for predicting the human response to inhalational anthrax.

Insufficient data is available to resolve which of the remaining two models he examined is most accurate. That answer will have to await further data from costly nonhuman primate experiments, should they ever be performed (none are planned). "We have to use both [models] right now, or use them as bounding cases," he advises.

Wilkening explored four policy issues that illustrate the consequences of choosing different models: 1) calculating how many anthrax-exposed people would become infected and how many would die; 2) assessing if decontamination would be needed; 3) determining how soon exposed people would show symptoms and how soon doctors would recognize those symptoms as anthrax; and 4) calculating how soon exposed people need to receive antibiotics to avoid contracting the disease.

"To figure out what happens in a bioterrorist event, you need to know two basic properties about the pathogen you're dealing with," Wilkening says. One is the dose-response curve, which determines the likelihood of becoming infected at different exposure levels--the higher the dose of anthrax you get, the higher the probability that you will become infected. The dose at which 50 percent of an exposed population becomes infected, called the ID50, is around 10,000 spores. The other basic property is the incubation-period distribution, or the time the pathogen takes to grow in the body before symptoms first appear.

Wilkening's study brought dose-dependence to a debate over how long the incubation period is for inhalational anthrax. Published data from vaccine efficacy tests in which nonhuman primates were challenged with high doses of anthrax--up to a million spores--indicate an incubation period of one to five days. Data from Sverdlovsk, which exposed people to low doses probably on the order of 1 to 10 spores, indicate a longer incubation period, about 10 days. Whereas previous authors have debated whether nonhuman primate experiments or the Sverdlovsk data should be used to determine the incubation period for inhalational anthrax in humans, Wilkening demonstrates that both estimates are correct, with the difference between them being due to the dose dependence of the incubation period and the very different doses received in each case.

"If you are exposed to a higher dose, there is a much higher chance that an anthrax spore will germinate quickly, thus leading to a shorter incubation period," he says. "Sverdlovsk was a low-dose exposure event and, consequently, one would expect anthrax spore germination to take a longer time, thus leading to a longer incubation period."

Truth and consequences

Russian officials confiscated the medical records of the Sverdlovsk victims and have so far refused to release details of what happened on April 2, 1979. "It would be nice to know exactly what happened, because that would allow us to model the event more accurately," Wilkening says.

Nevertheless, based on weather and other data from the day of the event, scientists think that around 2 p.m. spores, or dormant cells that revive under the right conditions, were released from a military facility, and the Bacillus anthracis spores spread up to 5 kilometers downwind. People breathed in the spores, which geminated and incubated in the body for between four to 40 days before people began to feel ill or show signs of illness such as sore throat, coughing, pains, aches and runny nose--the same symptoms as flu--that indicated they had entered what doctors call the prodromal phase. Within four days, people passed the point of no return, called the fulminant phase, in which toxins from the bacteria had built up to such an extent that people went into shock and died.

It's impossible to save those who've entered the fulminant phase and difficult to save those who've entered the prodromal phase. But if people can start treatment after exposure but before symptoms appear, there's a good chance that they will survive--a conclusion Wilkening draws from work by colleagues at Stanford's Center for Health Policy. Treatment primarily consists of antibiotics such as ciprofloxacin, doxycycline or penicillin. While a vaccine to prevent anthrax exists, it is not yet available for the general public but would be made available to people exposed to anthrax, according to the Centers for Disease Control and Prevention website.

In his study, Wilkening ruled out two of the four models because they either did not fit the Sverdlovsk data or the nonhuman primate data, or both. "There are two models that people have used that should no longer be used to predict fatalities, models B and C." (The four models used in his analysis are labeled A-D for convenience.)

Using the two remaining models A and D, he predicted that a hypothetical attack releasing 1 kilogram of anthrax spores in Washington, D.C., would infect between 4,000 and 50,000 people, most of whom would die if not treated quickly with antibiotics. The difference of a factor of 10, Wilkening points out, is "an uncertainty with which we must live for the time being until better data can resolve which of the models A or D is more accurate."

Regarding decontamination efforts, the higher the probability of becoming infected at low exposure levels, the greater the need for effective decontamination, especially for indoor environments. Spores "by nature are hardy," Wilkening says. In the soil, out of the way of sunlight, they can last for a decade. "Residual contamination can be a very serious problem in the wake of an attack," Wilkening says. "Unfortunately, both models A and D predict that residual surface contamination from anthrax spores will be a problem. Consequently, we need to come up with effective indoor decontamination strategies."

Analysts such as Professor Lawrence Wein of the Graduate School of Business are considering the issue. Last year, he assessed decontamination and concluded cleaning buildings to make them safe to reoccupy was a billion-dollar proposition.

In addition, the four models make very different predictions about when symptoms would occur. The day after exposure, they predict between 10 and 1,000 people feeling sick, with more people getting sick in the viable versus discredited models.

"In terms of detecting the outbreak rapidly, this is a good thing because it says that doctors could recognize it [sooner]," Wilkening says.

In terms of treating people before they reach the prodromal phase, however, this is a bad thing because people become sick quicker. Wilkening's analysis may help policymakers reassess how fast antibiotics need to reach people. His best model says administering antibiotics by day three saves 90 percent of exposed people. "Today we cannot meet the three-day requirement," he warns.

The nuclear regime in place since the Nonproliferation Treaty (NPT) took effect in 1970 is broken and needs to be fixed, the world's highest-ranking nuclear official told a half-full Memorial Auditorium in a wide-ranging lecture about the future of nuclear energy and weapons yesterday afternoon.

"We have a dysfunctional system -- system that cannot endure," said Mohamed ElBaradei, the director general of the International Atomic Energy Agency (IAEA). "We're reaching the fork in the road. Events in the last few years have made it clear that we need to change course."

The big news from ElBaradei's speech was his support for American entreaties to Iran. But the 2005 Nobel Peace Prize recipient also commented on North Korea, India, Pakistan, Iraq, terrorism, disarmament and the future of nuclear energy.

He said there are probably eight current nuclear states, excluding North Korea. He worried aloud that countries which can currently produce nuclear energy peacefully are only six months away from developing nuclear weapons for military purposes.

"Acquiring the technology to enrich uranium or reprocess uranium basically is the key to develop nuclear weapons as we have seen in Asia and Iran," he said. "They are virtually weapons states because in six months time if they decide for security reasons to develop their own weapon, they are there."

Iraq

While not a household name, ElBaradei was a prominent figure in the news as the lead weapons inspector in Iraq during the run-up to the 2003 American invasion. He said at the time that he could not find evidence of Iraqi weapons of mass destruction, but he would not conclude that there were no weapons in the country or that Saddam Hussein did not have a program.

ElBaradei asked for more time to complete inspections, but the Bush administration declined his request and decided to invade. The U.S. never found the nuclear and biological material that some had promised existed.

"Luckily...well I'm not sure luckily...we were proven right that there was no nuclear or any weapon of mass destruction in Iraq," he said. "But I hope that all of us have learned from the Iraq experience that we cannot just jump the gun. You have to be absolutely sure of the facts."

India

ElBaradei surprised observers when he supported the U.S. agreement with India earlier this year, which allowed the country to continue developing nuclear weapons and energy. He said the agreement with India did not endorse its proliferation activities but was indicative of the kind of outside-the-box thinking the international community needs when considering the spread of nuclear weapons and material.

"The end result is India coming closer and working with the rest of the world," he said. "It is not a perfect agreement, but it has a lot of advantages. From the safety, security and nonproliferation perspective, I see that agreement as a win-win situation."

Pakistan

Pakistan developed nuclear weapons as a response to India. Some have criticized Pakistan for its poor stewardship and control of the bomb, pointing out that weapons were almost fired during a skirmish over the disputed Kashmir region.

AQ Kahn, a senior nuclear scientist who helped Pakistan join the exclusive nuclear club, was caught selling compact discs and other information about bombs to several other countries.

"How much damage was done in the process we don't know," ElBaradei said.

The release of this nuclear material demonstrates the need for a "more robust verification system," he said, adding that Pakistan has come closer to the international community in recent years.

North Korea

Kim Jong Il expelled all IAEA inspectors in Dec. 2002, withdrew from the NPT in Jan. 2003 and announced in February 2005 that his military had a nuclear deterrent.

"North Korea is still a major problem," ElBaradei said. "We don't talk about it enough, but North Korea is declaring right now that they have a nuclear weapon. And the longer that they continue to be in that status, the more it is accepted in the collective conscious. This would be terrible because it will have a lot of negative ramifications in South Korea and Japan."

ElBaradei said ongoing negotiations are an important development but more needs to be done.

"What we see with the current six-party talks should have taken place years ago," he said.

Nuclear Proliferation

ElBaradei stressed that he understands the value of nuclear power, which produces much of the developed world's energy. Reducing its use would create more dependence on greenhouse gas-creating fossil fuels, he said.

"We need to use nuclear energy responsibly to maximize benefit and minimize risk," he said.

He said his "number one nightmare scenario" is a terrorist group acquiring nuclear technology since terrorists are not deterred by the possibility of reprisal.

In the post-Cold War world, ElBaradei said he could see no justification for the U.S. and Russia to maintain their nuclear arsenals on ready alert to fire with thirty minutes notice. He called on America to lead by example and continue to disarm its nuclear stockpile.

"Rather than pass judgment, I'd definitely like to say the U.S. should do more in leading by example in terms of nuclear disarmament," he said.

In September 2005, ElBaradei was reappointed to a third term as director general of IAEA. The United States had considered holding up his nomination but dropped its objections under pressure from European allies, who admire the former law professor from New York University.

Diplomat to the Core

The Egyptian native's sometimes broken English was interspersed with self-corrections and careful legalese nuance. ElBaradei answered questions posed by Political Science Prof. Scott Sagan, the director of the Center for International Security and Cooperation.

When Sagan made bold pronouncements about different country's nuclear activities, including the United States' "colossal failure" when North Korea violated the NPT, ElBaradei seemed careful not to point fingers, play the blame game or make enemies. Nonetheless, for a senior United Nations official, his speech was notably blunt.

"There's no international public servant whose integrity and work I admire more than yours," Sagan told ElBaradei.

Accompanied by his wife, ElBaradei spent the day at the University visiting with faculty and students. He spoke at a lunch sponsored by the Freeman Spogli Institute for International Studies and traveled to Sagan's home for a dinner with invited guests. He left the area at 8:30 p.m.

Today, the Senate Intelligence Committee will begin questioning Air Force Gen. Michael Hayden, nominated to be director of the Central Intelligence Agency, about the National Security Agency's collection of U.S. citizens' telephone records.

The scrutiny of the NSA is deserved, but the Senate and the American public may be missing a broader and more disturbing development. For the first time since the Civil War, the United States has been designated a military theater of operations. The Department of Defense -- which includes the NSA -- is focusing its vast resources on the homeland. And it is taking an unprecedented role in domestic spying.

It may be legal. But it circumvents three decades of efforts by Congress to restrict government surveillance of Americans under the guise of national security. And it represents a profound shift in the role of the military operating inside the United States. What's at stake here is the erosion of the principle, embedded in the 1878 Posse Comitatus Act, that the U.S. military not be used for domestic law enforcement.

When the administration declared the United States to be a theater of military operations in 2002, it created a U.S. Northern Command, which set up intelligence centers in Colorado and Texas to analyze the domestic threat. But these are not the military's only domestic intelligence efforts. According to the Congressional Research Service, the Pentagon controls "a substantial portion" of U.S. national intelligence assets, the traditional turf of the FBI and CIA.

In 2003, Congress created the job of undersecretary of Defense for intelligence to oversee the department's many intelligence bodies -- including a new entity called Counterintelligence Field Activity, or CIFA.

CIFA was ordered to maintain a "domestic law-enforcement database" on "potential terrorist threats" to U.S. military installations, and it began collecting information on U.S. citizens.

In 2005, a presidential commission suggested that CIFA, set up as a clearinghouse for information, be empowered to conduct domestic investigations into crimes such as treason, espionage and terrorism. Astoundingly, the commission declared that such an expansion of military powers would not require congressional approval; a presidential order and Pentagon directive would suffice. One Defense Department program feeding information to CIFA is TALON (Threat and Local Observation Notice), which is supposed to obtain data from "concerned citizens and military members regarding suspicious incidents" that could herald terrorist attacks. But the military appears to have interpreted its mandate broadly. A TALON report was filed on a protest against "war profiteering" by Halliburton, Newsweek reported. The protesters alleged the defense contractor overcharged for food for U.S. troops in Iraq.

Counterintelligence reports were also filed on New York University's OUTlaw, a decades-old organization of openly gay law students. "The term 'outlaw' is a backhanded way of saying it's all right to commit possible violence," concluded one misguided military investigator in a document obtained last month under the Freedom of Information Act." NBC reported that about four dozen TALON database entries on "suspicious incidents" were not about terrorism but about opposition to the Iraq war and military recruiting.

These misguided military forays into domestic surveillance harken back to Vietnam War-era abuses. This time, they are the result of a much broader intelligence-gathering effort by the military on U.S. soil. President Bush said last week, "We're not mining or trolling through the personal lives of millions of innocent Americans." But a 2004 survey by the General Accounting Office found 199 data-mining operations that collect information ranging from credit-card statements to medical records. The Defense Department had five programs on intelligence and counterterrorism.

The Defense Intelligence Agency, created in 1961 to provide foreign military intelligence, now uses "Verity K2" software to scan U.S. intelligence files and the Internet "to identify foreign terrorists or Americans connected to foreign terrorism activity," and "Inxight Smart Discovery" software to help identify patterns in databases. CIFA has reportedly contracted with Computer Sciences Corp. to buy identity-masking software, which could allow it to create fake websites and monitor legitimate U.S. sites without leaving clues that it had been there. The National Geospatial-Intelligence Agency is collecting data from 133 U.S. cities; intelligence sources told the Los Angeles Times that, when collection is completed, the agency would be able to identify occupants in each house, their nationality and even their political affiliation.

In 2002, the Defense Department launched the granddaddy of all data-mining efforts, Total Information Awareness, to trawl through all government and commercial databases available worldwide. In 2003, concerned about privacy implications, Congress cut its funding. But many of the projects simply transferred to other Defense Department agencies. Two of the most important, the Information Awareness Prototype System and Genoa II, moved to NSA headquarters.

The Pentagon argues that its monitoring of U.S. citizens is legal. "Contrary to popular belief, there is no absolute ban on intelligence" agencies collecting information on Americans or disseminating it, says a memo by Robert Noonan, deputy chief of staff for intelligence. Military intelligence agents can receive any information "from anyone, any time," Noonan wrote.

Throughout U.S. history, we have struggled to balance security concerns with the protection of individual rights, and a thick body of law regulates domestic law enforcement agencies' behavior. Congress should think twice before it lets the behemoth Defense Department into domestic law enforcement.

News that AT&T, Verizon and BellSouth gave customer records to the National Security Agency has set off a heated debate over the intricacies of espionage law. But legal or not, this sort of spying program probably isn't worth infringing our civil liberties for -- because it's very unlikely that the type of information one can glean from it will help us win the war on terrorism.

If the program is along the lines described by USA Today -- with the security agency receiving complete lists of who called whom from each of the phone companies -- the object is probably to collect data and draw a chart, with dots or ''nodes'' representing individuals and lines between nodes if one person has called another.

Mathematicians who work with pictures like this are called graph theorists, and there is an entire academic field, social network analysis, that tries to determine information about a group from such a chart, like who the key players are or who the cell leaders might be.

But without additional data, its reach is limited: as any mathematician will admit, even when you know everyone in the graph is a terrorist, it doesn't directly portray information about the order or hierarchy of the cell. Social network researchers look instead for graph features like ''centrality'': they try to identify nodes that are connected to a lot of other nodes, like spokes around the hub of a bicycle wheel.

But this isn't as helpful as you might imagine. First, the ''central player'' -- the person with the most spokes -- might not be as important as the hub metaphor suggests. For example, Jafar Adibi, an information scientist at the University of Southern California, analyzed e-mail traffic among Enron employees before the company collapsed. He found that if you naively analyzed the resulting graph, you could conclude that one of the ''central'' players was Ken Lay's secretary.

And even if you manage to eliminate all the ''central players,'' you may well still leave enough lesser players that the cell retains a complete chain of command capable of carrying out a devastating terrorist attack.

In addition, the National Security Agency's entire spying program seems to be based on a false assumption: that you can work out who might be a terrorist based on calling patterns. While I agree that anyone calling 1-800-ALQAEDA is probably a terrorist, in less obvious situations guilt by association is not just bad law, it's bad mathematics, for two reasons.

The simplest reason is that we're all connected. Not in the Haight-Ashbury/Timothy Leary/late-period Beatles kind of way, but in the sense of the Kevin Bacon game. The sociologist Stanley Milgram made this clear in the 1960's when he took pairs of people unknown to each other, separated by a continent, and asked one of the pair to send a package to the other -- but only by passing the package to a person he knew, who could then send the package only to someone he knew, and so on. On average, it took only six mailings -- the famous six degrees of separation -- for the package to reach its intended destination.

Looked at this way, President Bush is only a few steps away from Osama bin Laden (in the 1970's he ran a company partly financed by the American representative for one of the Qaeda leader's brothers). And terrorist hermits like the Unabomber are connected to only a very few people. So much for finding the guilty by association.

A second problem with the spy agency's apparent methodology lies in the way terrorist groups operate and what scientists call the ''strength of weak ties.'' As the military scientist Robert Spulak has described it to me, you might not see your college roommate for 10 years, but if he were to call you up and ask to stay in your apartment, you'd let him. This is the principle under which sleeper cells operate: there is no communication for years. Thus for the most dangerous threats, the links between nodes that the agency is looking for simply might not exist.

If our intelligence agencies are determined to use mathematics in rooting out terrorists, they may consider a profiling technique called formal concept analysis, a branch of lattice theory. The idea, in a nutshell, is that people who share many of the same characteristics are grouped together as one node, and links between nodes in this picture -- called a ''concept lattice'' -- indicate that all the members of a certain subgroup, with certain attributes, must also have other attributes.

For formal concept analysis to be helpful, you need much more than phone records. For instance, you might group together people based on what cafes, bookstores and mosques they visit, and then find out that all the people who go to a certain cafe also attend the same mosque (but maybe not vice versa).

While researchers at Los Alamos National Laboratory have used this tool to sift through hundreds of terrorism-related reports -- and find connections that human analysts could not have found easily -- it's still dangerous to rely on the math.

This is because, as Kennedy and Lincoln assassination buffs know, two people can be a lot alike without being the same person. Even if there is only a 1 in 150 million chance that someone might share the profile of a terrorist suspect, it still means that, in a country the size of the United States, two people might share that profile. One might be a terrorist, or he might be Cat Stevens.

This isn't to say that mathematicians are useless in fighting terrorism. In September 2004 -- 10 months before the bombing of the London Underground -- Gordon Woo, a mathematician and risk-assessment consultant, gave a speech warning that London was a hotbed of jihadist radicalism. But Dr. Woo didn't anticipate violence just using math; he also used his knowledge of London neighborhoods. That's what law enforcement should have been doing then and should be doing now: using some common sense and knowledge of terrorists, not playing math games.

Math is just a tool. Used wisely, math can indeed help in warfare: consider the Battle of Britain, won in part by breaking the German codes. But use it unwisely -- as seems to be the case here -- and your approval ratings might just hit a new all-time low.