A new study suggests a possible tie between the illness and brain damage. 

By Brigitt Earley
Updated April 11, 2016
Illustration of mosquito
Credit: Brown Bird Design

A new study offers evidence that Zika—the mosquito-borne virus that has many, particularly pregnant women, on edge—could cause even more neurological damage than initially thought.

The virus has previously been linked to microcephaly, a birth defect that causes unusually small heads in infants when contracted by expectant mothers, and Guillain-Barre Syndrome (GBS), a rare condition that attacks the nervous system. Now, according to a small study being released Monday at the American Academy of Neurology's 68th annual meeting in Vancouver, Canada, scientists say Zika may also cause an autoimmune syndrome called acute disseminated encephalomyelitis (ADEM). Researchers say the autoimmune disease, which attacks the brain and spinal cord, is similar to multiple sclerosis.

Researchers noticed a potential correlation between Zika and ADEM after following 151 people who came to Restoration Hospital in Recife, Brazil with symptoms associated with arboviruses, such as Zika, dengue, and chikungunya, from December 2014 to June 2015. Six of those patients developed neurologic symptoms that appeared to be caused by autoimmune disorders within 15 days of presenting symptoms consistent with Zika—fever, rash, muscle and joint pain, and red eyes. Further testing revealed all six of those patients had an autoimmune disease—four had GBS and two had ADEM. All of those individuals tested positive for the Zika virus.

"This doesn't mean that all people infected with Zika will experience these brain problems. Of those who have nervous system problems, most do not have brain symptoms," study author Maria Lucia Brito Ferreira, MD, with Restoration Hospital, said in a statement. "However, our study may shed light on possible lingering effects the virus may be associated with in the brain. Much more research will need to be done to explore whether there is a causal link between Zika and these brain problems."