WASHINGTON — As two Stanford University researchers described their experience watching public reactions in the initial days of the swine flu outbreak, it sounded like one of those nature films in which tiny fish dart back and forth in perfect unison.
The researchers were tracking thousands of Twitter posts pouring into an Internet site. With every twist and turn of the flu reports, the researchers noticed, the mass of tweets swung this way and that as if they were one, even though most of the individual Twitterers had no contact with one another outside of the website.
It was a rare window into the public psyche amid an explosion of information about a potentially dangerous disease outbreak.
The researchers -- James Holland Jones, an associate professor of anthropology, and Marcel Salathe, a biologist -- had devised an online survey to gauge people's anxiety about the H1N1 virus as it unfolded.
Posted early in the outbreak, the survey generated about 8,000 responses in a matter of days, but as doomsday predictions did not come to pass, responses dropped off -- a development that worried Jones.
"Swine flu is still out there and will be back next flu season," he said. "We've dodged the pandemic for now, but I think it's a very open question whether we have really dodged it."
The shifting reactions to H1N1 suggested that as the country has become more wired, people may move from indifference to anxiety and back in the blink of an eye.
After flu cases in Mexico soared at the end of April, U.S. government officials took to the airwaves, declaring a public health emergency as the World Health Organization raised the global threat level to 5 -- the second-most severe.
With little known about the virus, people's reactions were immediate: Travel to Mexico fell dramatically, pork-belly futures collapsed, and protective masks flew off the shelves. Mexico City virtually shut down -- closing gyms, restaurants, movie theaters and other nonessential businesses -- costing the already teetering economy $2.2 billion in 10 days, according to the nation's finance secretary.
But as the number of deaths in Mexico attributed to the disease plateaued at about 60 -- and as widespread U.S. fatalities failed to materialize -- the media coverage backed off, causing public interest to flag and some experts to fear that the early warnings may make it harder to get the public's attention in the future.
"We've cried wolf one too many times here," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.
"I actually think this situation has set us back. It really is two strikes, and now we're almost out," he said, referring to initial panic and then loss of interest in recent outbreaks such as SARS and avian flu.
More than 4 in 10 people followed news about the H1N1 outbreak very closely, according to a Pew Research Center survey. Even in a week filled with news of President Obama's first 100 days in office and Chrysler filing for bankruptcy, attention to news of the swine flu was so great, Pew found, that it became one of the top stories of the year to date.
Osterholm said the media had to be a crucial part of how health and government officials communicate during such an event. "We need to take a step back and see what we can learn from it -- how we should do it in the future," he said.
Initial public reaction to H1N1 was way out of proportion to the magnitude of the disease, said Richard Thaler, professor of behavioral science and economics at the University of Chicago.
"Psychologists say we have two brain systems, the old and the new," Thaler said. "The old one is fast and emotional. When we react by jumping in response to a snake, that's old. The new one is analytic. But often we don't get past the first emotional system."
The country is a bit on edge, Thaler said, and people on edge are less likely to react in a rational way. "It's hard to imagine a time when so much was going [on] on so many different fronts," he said.
He added that the Internet "is bad enough," but that the "velocity of rumor and gossip" had increased exponentially with Twitter.
Dan Ariely, author of "Predictably Irrational," invokes the concept of learned helplessness to describe how people behave when conditioned by a series of seemingly random, harmful events.
"When we have all these unexplained shocks, we just do what we're told," said Ariely, a professor of behavioral economics at MIT.
When people don't know how much risk to take in stressful situations, Ariely said, they look around to see what others are doing. But "if other people are doing foolish things," he said, many times "we do it too."