(CNN) -- Eight people in four states have died so far from an outbreak of a rare non-contagious fungal meningitis, an inflammation of membranes surrounding the brain and spinal cord.
The discovery of the outbreak, linked to an injectable steroid the patients were getting to treat pain, was first reported late last week by Centers for Disease Control and Prevention in Atlanta.
On Monday the CDC said 105 people across a total of nine states had been infected, and warned that the number will likely rise. Fungal meningitis is very rare and, unlike viral and bacterial meningitis, is not contagious.
How has this happened and does it touch your life?
Who is affected?
The patients were injected in their spine with a preservative-free steroid called methylprednisolone acetate. Some time after their treatment, the patients began reporting that they were feeling the hallmark symptoms of meningitis -- headache, fever, stiff neck and a sensitivity to bright lights.
The potentially contaminated injections were given starting May 21, 2012, with Tennessee so far reporting the most number of overall cases -- 35 cases, including 4 deaths. Other states reporting deaths are Maryland (1), Michigan (2) and Virginia (1). Updated case counts can be followed on this link to the CDC's site.
In addition to the four states where deaths have occurred, other states with confirmed cases are Florida, Indiana, Minnesota, North Carolina and Ohio.
The CDC says as many as 13,000 people may have received medicine from the potentially contaminated injections.
What should you do if you think you were infected?
According to the CDC, 75 facilities in 23 states received products from the company that produced the steriod. Health officials say any patients who received an injection at one of the facilities beginning July 1 and who began showing symptoms between one and three weeks after being injected should see their doctor right away.
Even if symptoms seem mild, call your doctor anyway.
In addition to typical meningitis symptoms like 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, medical experts say.
Once diagnosed, patients are treated with anti-fungal medication, which is given intravenously. That means a likely hospital stay, the CDC said. Patients may need to be treated for months.
Where specifically did the infectious material allegedly originate?
A Massachusetts-based pharmacy, the New England Compounding Center (NECC), has been linked to the injections. The NECC has voluntarily recalled all products that were distributed from its facility in the Boston suburb of Framingham. The company's web site was replaced with a note about the recall.
Products from NECC can be identified by markings that indicate New England Compounding Center by name or by its acronym, the note said.
How did officials know to focus on the New England Compounding Center?
A doctor at Vanderbilt University in Nashville, Tennessee, was recently treating a patient with meningitis. The patient wasn't improving for weeks and the doctor was growing increasingly concerned so the physician ordered more labwork. The tests revealed that the patient's spinal fluid had a fungus -- an extremely rare occurrence. The doctor asked the family if the patient had been treated for anything unusual recently, and the family explained that the patient had gotten injections for pain. The doctor then notified the Tennessee Department of Health.
Federal health inspectors began inspecting a New England Compounding Center plant on October 1 and found foreign particles in unopened vials. They ran tests and determined the substance was a fungus.
What is a compounding center?
Compound pharmacists create customized medication solutions for patients for whom manufactured pharmaceuticals won't work, according to the International Academy of Compounding Pharmacists.
Those mixed-batch drugs can range from children's cough syrup -- like adding a yummier grape flavor -- to complex concoctions that treat cancer, according to Kevin Outterson, an associate professor of health law and bioethics at Boston University.
There's little federal oversight of drug safety and quality at compounding pharmacies compared to big drug manufacturers, he said.
How does a steroid become contaminated with fungus, and how does the fungus hurt you?
It's unclear in this case how the steroids became infected.
Dr. William Schaffner, chairman of the Department of Preventive Medicine at Vanderbilt University Medical Center, said that when a company is creating a sterile pharmaceutical product, the facility as well as workers must adhere meticulously to good manufacturing practices.
"There's a whole book on these practices," he told CNN Monday. "Clearly, there was some violation."
Fungal spores are in the air around us, he points out, and they don't cause harm when they are inhaled. "When they are injected, it's a different story," he said.
If injected, the fungus invades small blood vessels and can cause them to clot or bleed. That can lead to stoke-like symptoms, Schaffner said.
In addition to typical meningitis symptoms like 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, Schaffner said, and they might not present for more than a month.
"That can make it very difficult to diagnose," he said. "That could be a huge challenge in this case."
Is the practice of compounding common in the United States?
Physicians and clinics are increasingly getting material from compounding pharmacies because they typically sell at a much lower cost than major drug manufacturers, according to Outterson.
"There's a lot of compounding that's going on. And there's been an increase in reliance on these pharmacies to deliver a product that couldn't be had otherwise -- for financial or medical reasons," he said.
One to three percent of all prescriptions dispensed in the United States are compounded on prescriptions for individual patients, according to the International Academy of Compounding Pharmacists which has 2,700 local pharmacists who provide a compounding service.
The academy estimates that there are 7,500 pharmacies in the United States that specialize in complex compounding services.
"It's good because drugs are expensive and that's a reality we have to deal with," Outterson said. "But it also begs the question, 'Should the FDA be regulating compounding pharmacies?' Some would say yes."
Why doesn't the FDA regulate compounding pharmacies?
All pharmacies are regulated by the state where they are located, but regulations vary state by state, Outterson said.
The FDA has tried to oversee these pharmacies, but the attempt failed. The FDA developed rules for compounding but litigation led to a U.S. Supreme Court ruling in 2002 that struck down the idea, Outterson said.
Congress has been unable to reestablish the FDA's authority over the pharmacies since.
What are officials doing about the outbreak?
The FDA, the CDC and the Massachusetts Board of Registration in Pharmacy are all investigating the outbreak.