(NEW YORK) -- Meningitis is an inflammation of the membranes that cover the brain and spinal cord, and is usually caused by a viral or bacterial infection. Viral meningitis tends to be less severe than bacterial.
Bacterial can cause brain damage, hearing loss, learning disabilities and even death, sometimes in a matter of hours.
According to the National Meningitis Association, about 1,500 Americans were diagnosed with meningitis each year between 1998 and 2007, and 11 percent died of the illness.
Among those who survived, about 20 percent suffer from long-term side effects, including brain damage, kidney disease, hearing loss or limb amputations.
"The numbers aren't that high, but when one of them is your kid, it doesn't matter what the numbers are," said Kelly Madison, president of the Meningitis Foundation of America.
Now, the New York City Department of Health and Mental Hygiene is reporting six new cases of bacterial meningitis.
Two Manhattan women in their 20s and a Staten Island woman in her 50s died from the illness in the past month.
The six patients ranged in age, from four to 47, but health officials said that strains of the infection were different and not likely linked.
In response to the six cases, the New York City Department of Health and Mental Hygiene sent a memo to health care providers across the city to remind doctors and nurses to report meningitis cases as soon as possible.
"We sent out an alert to remind doctors to report a meningitis case immediately, and also to remind them that, especially at this time of year, meningitis can look like the flu and other things," said Dr. Donald Weiss, director of surveillance for bureau of communicable disease investigator for the New York City Department of Health and Mental Hygiene.
While the six cases were not likely related, Weiss said that it's important for physicians to keep meningitis on their radar, especially during cold and flu season.
Warning signs of meningitis include fever, headache, nausea, fatigue, eye sensitivity to light, stiff neck, confusion and a purple skin rash that usually covers large parts of the limbs.
"A lot of these meningitis cases can feel like the carton variety flu, so it can be quite difficult to pinpoint, that's why you should look for things like severe headache and stiff neck, " said Dr. Lee Harrison, professor of medicine and epidemiology at the University of Pittsburgh Medical Center. "And the rash [along with other symptoms] should be an immediate red flag."
Copyright 2011 ABC News Radio