Health officials from Brazil and El Salvador are investigating the link between the Zika virus to a condition called Guillain-Barre syndrome, per the Associated Press. The rare nervous condition that can cause paralysis has alarmed health officials since the increase of the number of cases in relation to the Zika outbreak.

In Brazil, the first cases of Guillain-Barre syndrome were reported last May 2015, but the ailment is so rare in the country that officials are not tracking the number of cases. Most of those people that have the syndrome were also experiencing symptoms of Zika virus, which led to the investigation of the link.

However, the authorities are having difficulty in proving the link between Zika and Guillain-Barre because it takes weeks before symptoms for the syndrome to appear. Brazilian officials believe that the virus was introduced in the country via a tourist during the World Cup or a canoeing event back in 2014.

On the other hand, El Salvador health officials have reported 46 cases of the Guillain-Barre in a five-week span from Dec. 1, 2015 to Jan. 6 this year. Twelve out of the 46 cases have experienced fever and rashes, two of the known symptoms of the Zika virus.

"Guillain-Barré syndrome is an autoimmune disorder in which the body usually is responding to another infection. It has an immune response that destroys the covering of nerves and interferes with the ability of nerves to function and survive," Dr. Bruce Hirsch of the North Shore University Hospital in New York told CBS News.

"When it involves the muscles of respiration, people who have Guillain-Barré require a breathing machine in order to survive and get through experience," the doctor added.

The mosquito-borne Virus has also been linked with the birth defect called microcephaly, wherein a newborn baby suffers from head deformation caused by lack of brain development. The Brazillian Health Ministry has reported 3,500 cases of microcephaly and has already funded a research to create a vaccine to fight the virus, per FOX News.

The U.S. Centers for Disease Control and Prevention (CDC) has already issued a travel warning on Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Suriname and Venezuela. According to the CDC, eight countries and territories were added to the list namely Barbados, Bolivia, Cape Verde, Ecuador, Guadeloupe, Guyana, Saint Martin and Samoa.

In a report by Voice of America, the Zika virus was first discovered in 1947 by scientists in Uganda while studying monkeys. Before the 2015 outbreak in Brazil, the first serious epidemic of the virus happened in 2007 in the Pacific island of Micronesia with some additional cases in the Cook Islands, Easter Island, New Caledonia and Polynesia.