( CNN ) -- Doctors Without Borders has embarked on a massive vaccination campaign in three African countries to combat an outbreak of meningitis that has killed hundreds of people , the organization said Wednesday . A child gets vaccinated against meningitis in Niger in August 2007 . The vaccinations are being carried out in Niger , Nigeria , and Chad -- part of a large swath of what is known as the `` meningitis belt '' of sub-Saharan Africa , the organization said . The `` belt '' stretches from Senegal to Ethiopia . Doctors Without Borders , widely known by its French name , Medecins Sans Frontieres , said medical teams have treated and vaccinated 5.4 million people and plan on vaccinating another 1.7 million -- making the vaccination campaign the organization 's largest ever . The group said more than 1,900 people have died in this outbreak since January . More than 56,000 cases have been reported in Nigeria , Niger and Chad alone , the organization said . Last month , the World Health Organization said the disease was at epidemic level in 76 areas of in Niger and Nigeria , and a spokesman in Nigeria , Dr. Olaokun Soyinka , said the outbreak was `` bigger than usual . '' In March , the organization said a total of 24,868 suspected cases had been reported in the `` meningitis belt , '' including 1,513 deaths . The outbreak began around the start of the year , Soyinka told CNN . It usually peaks in the dry season because of dust , winds and cold nights , before dipping around May when the rains come , he said . Meningitis is an infection of the meninges , the thin lining that surrounds the brain and the spinal cord , according to the World Health Organization . Several different bacteria can cause meningitis but Neisseria meningitidis -- which is to blame for the current outbreak -- is one of the most important because of its potential to cause epidemics .
Doctors Without Borders embark on vaccination campaign to combat outbreak . Vaccinations being done in Niger , Nigeria , Chad , where over 56,000 cases reported . 5.4 million people have been treated , vaccinated ; 1.7 million more to be vaccinated . Over 1,900 people have died in this outbreak since January .