Of greater concern, however, was that people who'd just been exposed to a sneezing actor were three times as likely to want to spend $1.3 billion on the development of a flu vaccine instead of creating jobs in "green" industries than those who hadn't been near someone sneezing.

"Finding that a simple sneeze can shift feelings on an important decision -- how to spend a billion dollars -- should really lead people to be careful and think, 'Is my current feeling going to lead me astray?'" said study author Spike W.S. Lee, a doctoral student in social psychology at the University of Michigan, Ann Arbor. "We often make judgments without thinking about how we're feeling."

The study appears in the November issue of Psychological Science.

"Judgments are definitely context-dependent," said study co-author Norbert Schwarz, a professor of psychology and business at the University of Michigan. He said it was particularly telling that people from Michigan, where unemployment rates are skyrocketing, would favor funneling money into vaccine development instead of job creation.

"Most people felt that money was better spent on jobs, until someone sneezed, and that made the flu vaccine seem more important," he said. "Maybe a Congressman looking for health-care support should sneeze a lot."

Lee and his colleagues set up two different scenarios to assess how a sneeze could affect people's feelings and perceptions given the emergence of the H1N1 flu virus last spring. In the first scenario, 50 college students were selected to complete a one-page questionnaire about their risk of certain health outcomes, as well as their general feelings about the U.S. health-care system. Just before being given the questionnaire, an actor passing by 26 of the study volunteers sneezed and coughed.

When asked how likely it was that the average American would contract a serious illness, 26.7 percent of the control group answered affirmatively, compared to 41.2 percent of the sneeze-exposed group. The risk of dying from a heart attack before age 50 was a concern for 32.1 percent of the control group, compared to 45.4 percent of the sneeze-exposed group. The risk of dying from a crime or accident was perceived to be a real threat by 27.9 percent of the control group, compared to 41.2 percent of the sneeze-exposed group.

Those who'd been exposed to the sneezes were also more likely to feel the U.S. health-care system was in need of an overhaul.

In the second scenario, 47 people agreed to participate in a survey at a Michigan-area shopping mall. In this experiment, 23 were exposed to a sneeze and cough just before the survey, while the remaining 24 were not. All of the study volunteers were asked whether they would prefer that $1.3 billion be spent on flu vaccine development or the creation of green jobs. Only 16.7 percent of the controls felt that the money should be spent on flu vaccines versus 47.8 percent of the sneeze-exposed group.

"When someone sneezes, you get a little worry response that makes all kinds of things seem more dangerous. Usually, this worry response serves us well. We want to be alerted to risk, and we're usually less concerned with false positives than with possibly missing a real risk," said Schwarz.

"Fear can spread faster than any virus," said Dr. Marc Siegel, an associate professor of medicine and an internist at NYU Langone Medical Center. "Even if the mathematical model is correct, about one out of 80 people have gotten H1N1. That means there's a 79 out of 80 chance the person you heard sneeze doesn't have it," explained Siegel, who's also the author of several books, including Swine Flu: The New Pandemic.

"But, we're a nation of worried well. You're minding your own business and someone tells you you're going to die of something and then you worry about that and everything else that might kill you. We need to think about things in context. In this case, do what you can -- get the vaccine, wash your hands -- but remember it's a remote risk," advised Siegel.

More information

If you're worried about getting the flu, the U.S. Centers for Disease Control and Prevention has tips on staying well.