With the help of wireless sensors, Stanford researchers confirmed what most of us suspected. When it comes to infectious viruses, human beings are toast.
The researchers outfitted an entire high school population with IEEE 802.15.4 sensors for one day to model what they call a "human contact network." The devices tracked how often people came within the infection-spreading range of other individuals during a typical height-of-flu-season January day. Every teacher, student and staff member at the school carried a credit card-size TelosB device that sent and received signals every 20 seconds. The TelosB mote is a low-power programmable wireless sensor module specifically geared for research projects like this one. It uses the open source TinyOS operating system [link: PDF].
The TelosB mote was configured to broadcast every 20 seconds.
"The devices logged more than 760,000 incidents when two people were within 10 feet of each other, roughly the maximum distance that a disease can be transmitted through a cough or sneeze," according to a Stanford report on the project. With data in hand, the researchers ran thousands of simulations of a flu outbreak trying to determine infection rates under various circumstances. For instance, if only a small percentage of the population were to be vaccinated (as is always the case in real life) would it be better to vaccinate teachers or students? Is it important to vaccinate the most social (popular) students because they have more contact with others than classmates who keep to themselves? They also modeled if vaccinating a random sample of the population would be best.
The result: none of it mattered. Even kids who were not at the center of the social scene came within 10 feet of others. Viruses don't know the reason for proximity. When someone sneezes, the virus doesn't distinguish between a group of kids standing close to one another at their lockers pretending not to know one another, or a group of kids chatting in the hallway.
While each one of those three-quarter of a million contacts (in a single day) represents an opportunity to catch the flu, the news wasn't all bad. When factoring in human nature -- that a sick person isn't likely to finish the whole day of school/work -- it turns out that this factor will severely limit the number of others who catch the virus. "We assume that symptomatic individuals remove themselves from the school population after a few hours. We find that in 67.7% of all simulations, no secondary infections occur and thus there is no outbreak," the researchers report.
Of course, that means nothing if you happen to be in the remaining 32.3% that does catch the bug. A flu vaccine never seemed more appealing.