The CDC is specific in its diagnostic criteria: Patients must exhibit unexplained fatigue that is not related to exertion and cannot be relieved by rest. At least four other symptoms also must be present for six months of more, including impaired memory, unrefreshing sleep, muscle aches, joint pain, headaches of a new kind, sore throat or tender glands.
Rivka Solomon's battle with CFS began two decades ago at the age of 21 when she and two best friends contracted infectious mononucleosis.
"They were sick for a week and I was bedridden for a year," said Solomon, now 47 and founder of the Boston-based women's empowerment group, That Takes Ovaries.
Seven years later, her symptoms intensified after a bout with "walking pneumonia," and she was forced to give up a career in international politics and to confine her work to writing her book, "That Takes Ovaries," about women being "bold, gutsy and courageous."
"It's unrelenting fatigue and comes with non-restorative sleep," she told ABCNews.com. "You are damned exhausted all the freaking time. It's a deep, to-the-bone exhaustion.
"I feel like taking a shower," she said, "but putting my arms up to wash my hair is too much work. And it doesn't ever go away."
Like Toussaint, Solomon experiences a "brain fog," which feels like "you are thinking through a thick cloud of pea soup," and chemical and perfume smells make her "dizzy and wacky."
The very name itself is a stigma, according to Solomon: "It's so pathetic, like calling Parkinson's 'shaky person syndrome.'"
The CDC has called the new CFS research exciting, but preliminary.
"If I don't know the nature of the cases and controls, I can't interpret the findings," Dr. William C. Reeves, who directs public health research on the syndrome, told The New York Times.
"We and others are looking at our own specimens and trying to confirm it," he said. "If we validate it, great. My expectation is that we will not."
The CFS debate goes back to an outbreak in Lake Tahoe, Nev., in 1984. Several hundred patients developed flu-like symptoms, fever, sore throat, headache and neurological problems like memory loss.
The CDC dismissed the epidemic at the time, even though the patients were infected with several viruses, and suggested these were psychiatric problems, according to Hillary Johnson, the author of "Osler's Web: Inside the Labyrinth of the Chronic Fatigue Syndrome Epidemic."
The name was coined in 1987 and "functioned as kind of a social punishment," Johnson said in an op-ed piece for The New York Times. CFS, which now carries the scientific name X-associated neuroimmune disease, is associated with a high suicide rate.
In 1991, Dr. Elaine DeFreitas, a virologist at the Wistar Institute in Philadelphia, found retroviral DNA in 80 percent of 30 her patients with chronic fatigue. Some of them also had rare forms of cancer.
The CDC tried to replicate her efforts, but ended research prematurely and later criticized her work. The CDC acknowledged in 1999 that it had diverted millions of dollars allocated by Congress for CFS to other programs.
But at about the same time in the 1990s, University of Miami researcher Dr. Nancy Klimas pioneered lymph node extraction therapies for what was then called chronic immune activation syndrome.