ATLANTA (CNN) -- The number of documented U.S. cases of fungal meningitis has risen yet again, with the Centers for Disease Control and Prevention reporting 198 cases Saturday, including 15 deaths.
The latest tally is 14 more than the agency reported Friday. And Saturday's death toll is an increase of one more than the previous day, due to a fatality in Indiana.
Meningitis cases have been reported in 13 states thus far, with Tennessee the hardest hit at 52 documented infections and six deaths.
The cases have been linked to injections of a contaminated steroid produced by the New England Compounding Center.
Some 14,000 people may have received the injections, the CDC estimated this week.
A Minnesota woman, Barbe Puro, filed a lawsuit Thursday -- which may be the first of its kind -- against the Massachusetts pharmaceutical company at the center of the deadly outbreak. In it, she alleges she was injected in September with a tainted batch of steroids from the NECC.
Meanwhile, members of Congress on Friday expanded an investigation into the outbreak.
In a letter to the director of the Massachusetts Board of Registration in Pharmacy, leaders of the House Committee on Energy and Commerce noted the Food and Drug Administration sent the NECC a warning letter in 2006 "detailing significant violations witnessed" by investigators the previous year.
Massachusetts Gov. Deval Patrick also accused the NECC this week of misleading regulators and operating outside its license by shipping large batches of drugs nationwide. Plus, the state's pharmacy board mandated that all Massachusetts compounding pharmacies sign affidavits stating they are complying with state regulations requiring compounders to mix medications for specific patients.
Meningitis is an inflammation of the protective membranes covering the brain and spinal cord. It is usually caused by an infection, frequently with bacteria or a virus, but it can also be caused by less common pathogens, such as fungi in this case, according to the CDC.
Fungal meningitis is very rare and, unlike viral and bacterial meningitis, is not contagious.
Dr. William Schaffner, chairman of the Department of Preventive Medicine at Vanderbilt University Medical Center, told CNN that fungal infections are not usually mild. He said when a fungus invades small blood vessels, it can cause them to clot or bleed, which can lead to symptoms of small strokes.
In addition to typical meningitis symptoms such as headache, fever, nausea and stiffness of the neck, people with fungal meningitis may also experience confusion, dizziness and discomfort from bright lights. Patients might just have one or two of these symptoms, the CDC says.