"In the Southern Cone countries of Argentina and Chile, and in Brazil south from Sao Paulo, the prevalence is between 20 to 40 patients out of every 100,000 inhabitants," a number that "decreases notably in areas nearer the equator," Dr. Edgardo Cristiano, service chief of the Neurological Clinic and director of the Multiple Sclerosis Section of the Buenos Aires Italian Hospital, told EFE.

"In countries of the tropical area, the illness is much less frequent, but even in the Southern Cone, the area "of the greatest prevalence of the disease in Latin America, we still have 10 times lower incidence than in the Northern Hemisphere, which is to say northern Europe, the northern United States and Canada," he said.

According to Cristiano, close to 30 percent of multiple sclerosis victims are not adequately diagnosed or are under-diagnosed.

Under-diagnosis "chiefly occurs because multiple sclerosis is often confused with other illnesses," and "doctors and patients often attribute the symptoms to stress," the doctor said.

This is a disease of the central nervous system in which the immune system attacks the myelin, the fatty substance that sheathes the nerve cells and is essential for the functioning of the nervous system.

"While there may not exist a definitive cure, we have many alternative treatments that permit the illness to be controlled," Cristiano said.

Some 2.5 people in the world are affected by the illness, and in Latin America the number is somewhere between 50,000 and 100,000.

"Some theories say that on their raids and migrations into Europe, the Vikings possibly carried in their genes the predisposition to suffer from the disease," the expert said.

It chiefly occurs in cold or temperate geographic zones, and people of the white race are more vulnerable to it than blacks or Asians.

Women are twice as likely to come down with it as men.

The disease largely affects those between ages 20-40 and causes a strong socioeconomic impact on healthcare systems.

"Modern life can also have something to do with this increase, as might the lack of exposure to the sun to a certain degree," Cristiano said.