A study, carried out by Brazilian researchers, uncovered evidence that the virus may cause brain damage and produce symptoms similar to multiple sclerosis.
Dr Maria Lucia Brito Ferreira, from the Restoration Hospital in Recife, Brazil, said: "Though our study is small, it may provide evidence that in this case the virus has different effects on the brain than those identified in current studies."
During the study, researchers followed people who visited the hospital over a period of seven months with symptoms compatible with arboviruses, the family of viruses which includes Zika.
Six of these patients developed neurological problems, after reporting ordinary Zika-like symptoms such as fever, rashes, itching and muscle and joint pain.
Some of the neurological problems began straight away, while others appeared 15 days after the inital symptoms.
Two of the six were found to have developed acute disseminated encephalomyelitis (ADEM), a swelling of the brain and spinal cord which attacks the coating around nerves, while four developed Guillain-Barré syndrome (GBS), which affects the nervous system and has previous reported links to the Zika virus. Both can have serious impacts on health, but patients typically recover from them within a few months.
After being discharged from the hospital, five of the six had lingering problems with their motor skills, with some suffering from vision problems and reduced memory and thinking abilities.
Worryingly, tests revealed all of the patients had the Zika virus, and not other arboviruses like dengue or chikungunya.
Dr Ferreira was keen to point out: "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."
"However, our study may shed light on possible lingering effects the virus may be associated with in the brain."
Although the study was small and further research is needed, it may provide further evidence that Zika could have serious effects on ordinary patients, not just pregnant women, who are thought to be the most at-risk group due to the suggested links between the virus and microcephaly in their unborn children, a disorder which causes babies to have abnormally small heads.
Dr James Sejvar, from the American Centre for Disease Control and Prevention, said: "At present, it does not seem that ADEM cases are occuring at a similarly high incidence as the GBS cases, but these findings from Brazil suggest that clinicians should be vigilant for the possible occurrence of ADEM and other immune-mediated illnesses of the central nervous system."
He said the main question facing researchers is why Zika appears to have such strong associations with these neurological problems, adding: "Hopefully, ongoing investigations of Zika virus...will shed additional light on this important question."
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