Meningitis, a rare and possibly fatal disease, has seen outbreaks in the nation's three biggest cities in recent years. In Chicago, Los Angeles and New York City, it has disproportionately impacted gay men, and officials aren't sure why.

Since June 2015, there have been nine cases in Chicago, including one death -- all impacting gay men. L.A. County has had 15 cases of meningitis this year -- eight of those gay men. And New York City has had 22 cases -- all among gay men -- that resulted in seven deaths from 2010 to 2014.

"True, we are talking about 13 cases in L.A. But 13 cases is too many for a completely preventable disease," said Robert Bolan, the medical director of the Los Angeles LGBT Center.

Meningitis, which has symptoms similar to those of the flu, is spread through continuous close contact -- think college students living in dorms. It causes inflammation of the spinal cord and brain, which can lead to brain damage or death in just hours or days if left untreated. There's a vaccine but only for some of the disease's bacterial and viral strains.

Officials also worry that the new cases may have been sexually transmitted, which would be a new development in the disease's history.

Sarah Kemple, medical director of the communicable diseases program at the Chicago Department of Public Health, can only guess why the outbreaks are affecting gay men more than others.

"Men who have sex with men tend to have very tight-knit social networks, similar to what you would see among colleges,” she said.

After L.A. County had an outbreak in the gay community two years ago, Bolan wrote to the Centers for Disease Control and Prevention (CDC) asking them to research the connection between gay men and intermittent meningitis outbreaks in large urban areas. The CDC and the New York Department of Public Health launched that study this year -- and has since extended it to L.A.

The three cities have started working together to figure out the best ways to eliminate the disease and keep it from spreading within and outside their jurisdictions.

“Our key objective is to get the vaccine out there, and we’ve made broad strides there,” said Kemple.

As part of new public awareness campaigns in Chicago and L.A., both cities have started offering the meningitis vaccine for free at local gay health centers and events targeting the LGBT community. In Chicago, the vaccine is also now offered at various Walgreens locations.

For health officials in other urban areas, Kemple advises getting ahead of the curve now.

“Start bringing awareness to the vaccine and connect with providers that serve gay populations so they can start informing their patients about the need to get vaccinated,” she said.

Despite the concern among health officials that the disease will spread to gay communities in other large cities, Bolan is hopeful now that the CDC is on the case.

“We’ve reached a tipping point with the CDC," said Bolan. "It’s now on everybody’s radar."