An urgent shortage of blood and stem cells in the black community is costing lives, Canada’s blood agency warns.

When 12 students at a high school in New York suddenly developed strange symptoms like stuttering, uncontrollable twitching movements and verbal outbursts, the community was concerned. Was there something in the environment? Was it a virus of some sort spreading dangerously? Three students and one adult have since also exhibited the same symptoms. Doctors at DENT Neurologic Institute have now diagnosed some of the girls with "conversion disorder," leaving people even more confused. What is conversion disorder? A person with conversion disorder has neurological symptoms that aren't related to any known neurological condition, according to the American Psychiatric Association. The symptoms could appear as uncontrolled motions or verbal outbursts, like the students in New York, or as anything from weakness or paralysis to a loss of vision or hearing. In diagnosing conversion disorder, doctors must first rule out other neurological diseases and determine that the symptoms are not being intentionally faked. Often the symptoms are inconsistent with typical signs of a neurological disease – either physical signs or those that might show up on a diagnostic test. What causes conversion disorder? Stress is the main underlying cause of conversion disorder, says Dr. Jay Salpekar , director of the Neurobehavioral Program at Children's National Medical Center in Washington. That stress can be physical or psychological, and the amount that would cause the disorder varies in every person. "The bottom line is that this stress is somehow converted into a physical symptom," Salpekar says. "Everybody has their breaking point." Stress can also aggravate another underlying medical condition that was previously undiagnosed – and may never be. "We have many tools available with modern medicine, but we don't know everything." What's the difference between conversion disorder, mass psychogenic illness and mass hysteria? The official name for this disorder is still being debated. The American Psychiatric Association's current Diagnostic and Statistical Manual – or DSM-IV – calls it "conversion disorder." The new version, DSM-5, which is set to publish in May 2013, is proposing a change to call it functional neurological disorder. In the past, the disorder has been called mass psychogenic illness or, more simply, mass hysteria. All the names describe the same disorder. It's important to note that conversion disorder is not a group diagnosis, but an individual one. "It's very unusual to have conversion symptoms that are 'contagious,' " Salpekar says. Psychiatrists often refer to cases like the one in New York as a conversion reaction – or a group's reaction to conversion disorder. Has this happened before? Conversion disorder on an individual basis is common, Salpekar says. Conversion reaction hasn't been well documented. Most of the people involved in group incidents don't seek mental health help and are never officially diagnosed with conversion disorder. Conversion reaction can be cultural, as it was in Trinidad in 2010 when students at a secondary school started screaming and collapsing. The phenomenon was attributed to demonic possession, according to a local newspaper , which may have helped it spread. In 2007, nine students and a teacher at William Byrd High School in Roanoke, Virginia, complained of "involuntary movements in the extremities," according to The Roanoke Times . Environmental tests done at the school came up clean. While the principal told CNN that six students were determined to be faking, the Virginia Department of Health did an investigation and concluded the students' symptoms were consistent with "mass psychogenic hysteria." In 2004, 31 chorus members at Starpoint High School in Lockport, New York, fell ill within an hour. Tests on the students and the building couldn't determine a cause, and everyone recovered quickly, according to a local news report . The list goes on: in 2007, 14 female high school students in Florida   who developed sudden loud breathing problems; in 1982, 100 people in Los Angeles who  thought they had food poisoning , but didn't; in 1977, factory workers in West Virginia who passed out by the dozens . Is it always women? Many of these examples involve a group of young female students. But Salpekar warns against taking that as a sign conversion disorder or reaction only happens to women. Females are just more likely to seek help or bring attention to their symptoms, he says. Are we sure it's not just a hoax? Some people obviously do fake symptoms – psychiatrists call them maligners. These people always have something to gain from doing so, whether it's money in a lawsuit or a long stint off from work. But few people intentionally make up symptoms that make their lives more difficult for no reason, Salpekar says. "To say that they're faking, it's just inappropriate. People do not fake things that adversely affect their life in such a way. … [Conversion disorder] is simply a reflection that something is wrong in the mind, brain and body." Can it be treated? Yes. First, doctors treat any underlying medical or psychological conditions. Anti-anxiety drugs can be prescribed to help with the stress, according to the Mayo Clinic . Counseling is used to calm symptoms and teach stress management techniques. Other treatments include physical therapy to help with uncontrollable movements, hypnosis and/or magnetic stimulation in the brain. Filed under: Medical Mysteries , Mental Health , Mind and body Tagged: Jacque Wilson- CNN.com Senior Associate Producer

Trichloroethene (TCE) has become a chemical of interest after environmental activist Erin Brockovich suggested that the derailment of a train carrying chemicals 41 years ago could be involved in the mysterious illness striking 16 people, mostly high school students in New York. Brockovich’s team was dispatched to the Le Roy Junior/Senior High School, in Le Roy, New York, this week to collect water and soil samples. The school is more than three miles from the train wreck site, but some worry that the school was built in 2006 with contaminated supplies. The school district has called the speculation a “distraction” and a “publicity stunt.” The New York State Department of Health, the New York State Department of Environmental Conservation and the Environmental Protection Agency have been involved. But the agencies have not found an environmental or infectious cause, according to a school district statement. TCE was one of 58 different chemicals and 63 pesticides tested for; the results showed nothing out of the ordinary, according to the state’s health department. The National Institutes of Health has offered the students free evaluations of their cases for possible involvement in clinical studies it is doing on conversion disorder. Why is there speculation about TCE? The theory about the environmental connection surfaced after one of the families affected by the mysterious ticking received an anonymous note in their mailbox about a train derailment in 1970, Brockovich told Dr. Drew Pinsky on his HLN show. That note suggested that contaminated rocks and soil were used to build the school. The site of the train derailment in Le Roy is on the Superfund National Priorities List. A Superfund site means that it’s a hazardous waste site that is placed on the EPA’s list to assess health impact. In the accident in 1970 , a Lehigh Valley Railroad train spilled one ton of cyanide crystals and around 30,000 gallons of trichloroethene onto the ground, according to the EPA Superfund site. TCE has been found in at least 761 of the 1,430 Superfund sites in the country. What is TCE? TCE, a watery chemical that smells like chloroform, has been used as an industrial solvent for cleaning metal parts, according to the Agency for Toxic Substances and Disease Registry. It is also used to make other chemicals such as cleaner, paint stripper and adhesives. It was once used as anesthesia, until its use was banned in the 1970s. How long can TCE stick around? It is a potentially harmful contaminant that can easily evaporate into the air. Its half-life in the air is about seven days. It is not a persistent chemical in the atmosphere. But TCE is not very soluble in water and is detected in ground water. This could be a source of exposure. The New York health department tested for TCE and collected samples throughout the building. The tests found nothing out of the ordinary, according to the agency. Is TCE exposure common? Most people have traces of TCE in their bodies, because the chemical is in the water, soil, food and environment. It can even be found in breast milk, said Dr. Samuel Goldman, an associate professor at the Parkinson's Institute and Clinical Center. “You can detect it in humans,” he said. “Its half-life in humans is short. You could detect it in blood and metabolites in urine.” The chemical is usually expelled from the human body quickly. “TCE is rapidly cleared from the body, and these nervous system effects subside as soon as the TCE level in the body decreases,” said Dr. LuAnn White, director of the Tulane Center for Applied Environmental Public Health Sciences. What are the known health effects of TCE? As is the case with most solvents at high doses, acute exposure to TCE can cause effects on the nervous system such as dizziness, headache, nausea, confusion, lack of coordination and drunk-like sensations, according to the EPA. Drinking or breathing high levels of trichloroethylene could cause nervous system effects, liver and lung damage, abnormal heartbeat, coma and possibly death. Goldman, who published a small study about TCE and its possible link to Parkinson’s disease , said he received e-mails from people living nearby Le Roy who have concerns about TCE. “I am not aware of any literature on TCE that would link it to those symptoms,” Goldman said about the uncontrollable movements and verbal outbursts among the 16 people in New York. “But what I told them was if they were very concerned about the effects of this spill that occurred 40 years ago, they should check their water supply for TCE.” Chronic exposure to TCE could cause kidney cancer and non-Hodgkin’s lymphoma. “The work looking at neurological effects of chronic exposure is very little,” Goldman said. CNN's senior medical producer Danielle Dellorto contributed to this report. Filed under: Environment , Pollution Tagged: Madison Park – CNNhealth.com Writer/Producer

A federal system was established in 2005 to help track potentially deadly food-borne illnesses. Yet fewer than half of its tracking sites are in place, with no timeline for completion.