The Justice Department is working out whether it can officially close the investigation of the 2001 anthrax attacks after scientist Bruce Ivins, described as the prime suspect, killed himself last week.
Even if the case is closed, though, the government still has to prepare for any future attacks or natural contagions.
Since the attacks, the federal government has spent about $50 billion to improve the way it detects and responds to biological threats. But progress has been limited, and some security experts say the threat is greater than it was.
A federal official in charge of monitoring biological threats says it's unlikely that a bioterrorist attack could be stopped. Robert Hooks, a deputy assistant secretary at the Department of Homeland Security, told a congressional panel last month that's why the government has focused on detecting whether an attack has already occurred, so authorities can respond.
Sensors have been placed around major cities to monitor the air for deadly pathogens. Vaccines and antibiotics have been stockpiled. And Hooks said a new national biosurveillance center will be ready to go next month.
To that, another witness, William Jenkins of the Government Accountability Office, responded, "We wish them luck. ... But I think it may be a little bit optimistic."
Few dispute that the challenges of defending against a biological attack are huge.
"In some ways, the more we look at the problem, the harder it seems to get," says Gerald Epstein, a senior fellow at the Center for Strategic and International Studies. He says much of the progress since 2001 has been in recognizing how vulnerable the country is.
Epstein says that has raised a whole host of questions — like, how do you provide emergency medical treatment quickly to a lot of people?
"How are you going to set up the distribution sites? Making sure you even have something to hand out. Finding out when the attack actually occurred so you can start that process. Having your political leaders have enough confidence in the decision to go ahead and order a massively disruptive response like that," he says.
Right now, the answers are incomplete. Randall Larsen, head of the Institute for Homeland Security, a think tank, says he gives the federal government high grades for having truckloads of emergency medical supplies ready to send out quickly.
"The problem is, the federal government gets an A-plus, [but] most cities get Ds or Fs because they don't have a system to rapidly dispense it, to break down those large quantities and get it out in a rapid manner to the citizens," Larsen says.
Epstein says that raises other concerns: Should people go to distribution sites to get vaccines or antibiotics? Or is it better if medical supplies are delivered to people's homes, so they can stay out of harm's way?
Tara O'Toole, director of the Center for Biosecurity at the University of Pittsburgh Medical Center, says progress since 2001 has been disappointingly slow.
"In particular, I think we miscalculated on how fragile and starved of resources the public health system truly is," she says.
Many hospitals are better prepared than they were in 2001, she says, but they're not ready for mass casualties. She also notes that recent advances in the biosciences, while beneficial, also have a downside.
"As we go forward, it's going to get easier and easier to engineer organisms into new kinds of biological weapons," O'Toole says, adding that it also will be increasingly difficult to control who has access.
O'Toole and others say that for all the money that's been spent so far, a lot more is needed — and that the government has to be better organized.
"There are 26 presidentially appointed, Senate-confirmed people working in biodefense in the federal government," Larsen says. "Not one has it as a full-time job, and no one is in charge."
In fact, the new biosurveillance center at the Homeland Security Department is supposed to improve that coordination. But GAO's Jenkins notes that, so far, the department has agreements with only six of the 11 federal agencies it plans to start coordinating with next month.