With Facebook, you can track down buddies from high schools, ex-girlfriends/boyfriends (for better or worse), long lost cousins... and infectious diseases. Last year, public health officials in Minnesota capitalized on a tip from the social media platform to hunt down the source of a strep throat outbreak in a high school.

The tip came from a parent whose daughter was a member of the high school's female dance team. After noticing that an alarming number of the dancers had posted to the team's Facebook page with complaints of strep throat, or Group A streptococcus (GAS) pharyngitis, the observant guardian contacted the Minnesota Department of Health.

The health officials realized that posts to the Facebook page began to appear 24-48 hours after the team had thrown a banquet and about three days after a potluck with some male classmates.

Although strep throat is normally passed via people coughing up infected respiratory droplets, food contamination does occur in rare cases. This route was more common before modern refrigeration and the advent of pasteurization, especially through the consumption of raw milk.

The investigators started with classic detective work: 100 telephone interviews and nasal swabs from the attendees, associated family members, and male classmates. Leftover food was bagged, and all of the biological specimens were transported to the state's public health laboratory in St Paul.

All of the boys who attended the potluck were negative for strep, so this event was eliminated.

Individual leftover items from the banquet that were tested by 'DNA typing,' a form of genetic analysis that can decipher bacterial heritage. The health team found that only a pot of pasta contained GAS bacteria that matched the cultures collected from the dancers.

A couple of false leads — people who had GAS but did not attend the banquet — could have thrown the investigators, but DNA typing allowed them to precisely track the gene fingerprints of the bacteria in the pasta to the infections in the dancers.

Another set of interviews revealed that the parent who had made the pasta, along with their child, had caught the same variant of GAS over two weeks before the banquet. Furthermore one girl who hadn't attended the banquet, but eaten the leftover pasta, came down with this strain of strep. In other words, the food culprit was caught.

"We suspect cooked food was contaminated by respiratory droplets from a person who carried the strep bacteria in the throat when the food was cooling or reheating," said lead investigator and epidemic specialist Dr. Sarah Kemble of the Minnesota Department of Health. "The food probably was not kept hot or cold enough to stop bacterial growth."

To reduce the spread of foodborne illness, the authors recommended that large batches of prepared food be kept either hot or cold, as disease-causing bacteria love to roost at temperatures between 41°F to 140°F. People should also avoid cooking for groups if they have symptoms of a respiratory disease like strep and should always ask a doctor how long they should wait before prepping meals for others.

This isn't the first mysterious outbreak to be cracked by Facebook. Flu flare-ups have been identified using the popular social media tool.

Google Flu Trends and other websites like HealthMap have tried to harness the power of people conducting influenza-related searches when they are sick, but some have questioned whether these tactics are truly representative of an afflicted population, given not everyone is online. In addition flaws appeared in Google's system during America's severe bout of seasonal influenza this past spring, with search engine app dramatically overestimating the prevalence of the disease.

Odds are these computer bugs will be worked out by intrepid software programmers, and disease surveillance, like so many aspects of public life, will be added to the list of items that social media has revolutionized.

Source: Kemble SK, Westbrook A, Lynfield R, et al. Foodborne Outbreak of Group A Streptococcus Pharyngitis AssociatedWith a High School Dance Team Banquet-Minnesota, 2012. Clinical Infectious Diseases. 2013.