Enlarge / The Plaza Mayor or Plaza de Armas of Lima in Peru, part of a Unesco world heritage site in Lima. (credit: Getty | Frédéric Soltan/Corbis)

Over 230 people in Peru have developed a rare, paralyzing neurological disorder called Guillain-Barré Syndrome, leading government officials to declare a national emergency and the World Health Organization to send out a disease outbreak alert.

So far, four people have died from the disorder, which involves the immune system attacking peripheral nerves. It often starts with progressive muscle weakness and numbness that can lead to paralysis and, in about a quarter of the cases, the need for mechanical ventilation.

Peru—a country of over 34 million people—typically sees fewer than 20 suspected cases per month of Guillain-Barré Syndrome (pronounced ghee-yan bar-ray or abbreviated GBS). But, between June 10 and July 15, the country tallied 130 cases, including the four deaths, bringing the year’s total to 231, the WHO reported Tuesday.