Federal and state health officials are investigating an outbreak of meningococcal disease in Florida primarily infecting men who identify as gay, bisexual or men who have sex with men.
As of Tuesday, at least 24 cases have been confirmed and seven people have died, according to the Centers for Disease Control and Prevention.
The outbreak is so severe that the federal health agency is calling it "one of worst outbreaks of meningococcal disease among gay and bisexual men in U.S. history."
What's more, the Florida Department of Health said the number of cases identified has surpassed the five-year average of meningococcal infections in the state.
"It's concerning because it has a pretty high fatality rate," Dr. Peter Chin-Hong, an infectious diseases specialist at the University of California, San Francisco, told ABC News. "This is not like an annoying rash or something like a boil. This is something that can actually kill you … even if you receive antibiotics."
Meningococcal disease refers to any disease caused by a specific type of bacteria including meningitis, which occurs when the lining of the brain and spinal cord become inflamed.
Symptoms included headache, fever, stiff neck, nausea, vomiting and -- if the disease gets into the bloodstream -- a dark purple rash, according to the CDC.
The disease spreads when bodily fluids, mainly saliva and spit, are exchanged. But the disease generally requires prolonged close contact, making it less contagious than the common cold or the flu.
About one in 10 people have the bacteria in the back of their nose or throats but don't become ill, making them "carriers," the federal health agency said.
Meningococcal disease can be deadly with about 10% to 15% of all people who fall ill dying, according to the CDC.
Although the disease has been primarily identified in the gay and bisexual community, there is currently no evidence that it is a sexually transmitted infection.
Certain people are at higher risk for being infected, including those who live in crowded places or have HIV, but it is not a so-called "gay disease," Chin-Hong said.
"In fact, more people who are not gay get meningococcal infection. It's just that this outbreak has been among men who have sex with men," he added. "Numerically, when you look at the statistics, more non-MSM have it including college kids [and] older adults."
Chin-Hong said the risk to the public is low because meningococcal outbreaks tend to be regional and typically do not spread from state to state.
But he urged people to follow the CDC's advice, which is that anyone who identifies as gay, bisexual or men who have sex with men gets a meningococcal vaccine if they live in Florida or plan on traveling to Florida.
"Getting vaccinated against meningococcal disease is the best way to prevent this serious illness, which can quickly become deadly," Dr. José Romero, director of the CDC's National Center for Immunization and Respiratory Diseases, said in a statement.
He continued, "Because of the outbreak in Florida, and the number of Pride events being held across the state in coming weeks, it's important that gay and bisexual men who live in Florida get vaccinated, and those traveling to Florida talk to their healthcare provider about getting a MenACWY vaccine."
Neither the CDC nor the FDOH replied to ABC News' request for comment.