For many of us, our teen years consisted of increasingly close contact with other teenagers. From going to the park to play basketball to crashing at a friend’s place with a bunch of others to getting intimate with our first girlfriend (or boyfriend), these forms of contact grew in the frequency with which they occurred until we were living among other people our age in our college dorms. Besides an increased chance of getting bed bugs, mono, and the common cold, teens living in such close quarters also put themselves at a higher risk of deadly meningitis.

The risk of teens getting meningitis has always been high, and it’s long been believed that it was due to their tendencies to live and mingle in close quarters. A new study, however, has discovered that there may be another reason: The bacteria that causes meningitis, Neisseria meningitidis, contains genes that allow it to use a small fatty acid in teens’ bodies, called propionic acid, to grow further. “The propionic acid is generated by other, strictly anaerobic bacteria (bacteria that do not need oxygen to live) that become more prevalent in adolescents,” said lead author of the study Dr. James Moir, of the University of York’s Department of Biology, in a press release.

According to the Centers for Disease Control and Prevention (CDC), almost 10 percent of all people have N. meningitidis lurking in the back of their noses or throats. These people are called “carriers” because they may not ever become infected. Nevertheless, once the bacteria is spread through secretions from these body parts, such as saliva, symptoms will begin to develop after about three to seven days. At first, the infection will cause nausea, vomiting, increased sensitivity to light, and altered mental states. As it eats away at the connective tissues protecting the brain and spinal cord, called the meninges, and enters the blood stream, it becomes increasingly deadly.

“Through our research, we identify the metabolic pathway responsible and show that there is a correlation between N. meningitidis and propionic acid generating anaerobic bacteria Porphyromonas and Fusobacterium,” Moir said. “The anaerobes are acquired gradually with age, peaking in adolescence.” Besides supporting the higher risk of teens to acquire meningitis, the findings also help to explain why concentrations of N. meningitidis vary with age.

For teens hoping to avoid getting meningitis, the CDC emphasizes the importance of getting vaccinated. If you know of anyone who has meningitis, and are in constant contact with them, the CDC also suggests taking antibiotics in a form of treatment known as prophylaxis.

Source: Jones H, Moir J, Edwards J, et al. A large genomic island allows Neisseria meningitidis to utilize propionic acid, with implications for colonization of the human nasopharynx. Molecular Biology. 2014.