Volunteers were asked to spend one school day wearing matchbox-sized sensor devices--called motes--on lanyards around their necks.
Like a cell phone, each mote was equipped with its own unique tracking number, and each mote was programmed to send and receive radio signals at 20-second intervals to record the presence of other nearby motes.
Volunteers then were asked to go about their day by attending classes, walking through the halls, and chatting with other people.
At the end of the day, Salath's team collected the motes and recorded how many mote-to-mote interactions had occurred, and how long each interaction had lasted.
"An interaction isn't necessarily a conversation," Salath said.
"Even when people aren't talking, they might be sneezing and coughing in each other's direction, bumping into each other, and passing around pathogens."
To record even these non-conversational events--any kind of spatial closeness that would be enough to spread a contagious disease--each mote used a 3-meter maximum signaling range, extending outward from the front of the person's body.
Defining a single interaction as any 20-second or longer event of mote-to-mote proximity, Salath and his team found that the total number of close-proximity events was 762,868.
"The same two people may have had many very brief interactions," Salath said. "Still, we have to count each brief interaction individually, even between the same two people."
"From a pathogen's point of view, each interaction is another chance to jump from person to person."
In addition, the team found peaks of interactions at times between classes, not surprisingly, when mote-wearing volunteers were physically closer to one another, moving around in the halls on their way
|Contact: Cheryl Dybas|
National Science Foundation