According to Colorado State University's Janice Moore and Chris Reiber, a biomedical anthropologist at Binghamton University, in New York, there is a strong possibility that the flu virus might boost our desire to socialize. Why? Because it spreads through close physical contact, often before symptoms emerge -- meaning that it must find a new host quickly.

To explore this hunch, Moore and Reiber tracked 36 subjects who received a flu vaccine, reasoning that it contains many of the same chemical components as the live virus and would thus cause the subjects' immune systems to react as if they'd encountered the real pathogen.

The difference in the subjects' behavior before and after vaccination was pronounced: the flu shot had the effect of nearly doubling the number of people with whom the participants came in close contact during the brief window when the live virus was maximally contagious.

"People who had very limited or simple social lives were suddenly deciding that they needed to go out to bars or parties, or invite a bunch of people over," says Reiber. "This happened with lots of our subjects. It wasn't just one or two outliers."

So there you have it. A made-to-order excuse for the next episode of pub-crawling, should you need one. And maybe also an explanation for why people who are coming down sick with the flu insist on coming to work anyway, thus sharing their misery with everyone in the office.

[Paraphrased from article in the Atlantic, "How Your Cat is Making You Crazy" by Kathleen McAuliffe.]