Scientists studying Zika have for the first time found a possible link between the virus and a neurological syndrome that can cause temporary paralysis, according to a study published in the medical journal The Lancet.
The majority of patients diagnosed with the Guillain-Barre syndrome during an outbreak of Zika in French Polynesia in 2013 and 2014 had recently showed signs of Zika infection, the scientists said in the study.
Guillain-Barre is not the same as microcephaly, a congenital condition whose suspected link to Zika prompted the World Health Organization (WHO) to declare a public health emergency.
A relatively rare syndrome, Guillain-Barre is frequently caused by infections or other illnesses. It causes the body's immune system to damage its own nerves, resulting occasionally in muscle weakness and paralysis.
To determine whether Guillain-Barre was linked with Zika, scientists tested a set of patient cases against two control groups, including one group that was treated for a non-febrile illness. Fever is one of the most common symptoms of Zika and other mosquito-transmitted diseases.
Ninety-eight per cent of those tested with Guillain-Barre had Zika antibodies, compared to 56 per cent in the first control group. Most cases of Guillain-Barre had antibodies that indicated that the patient had experienced a Zika infection in the days before developing the syndrome.
Among the cases of Guillain-Barre analyzed from French Polynesia, 38 per cent were admitted to intensive care. None of the patients died, and 57 per cent of patients were able to walk without assistance three months after being discharged, the study said.
Zika has been documented in more than 30 countries, most of them in the Americas. The virus usually causes only mild symptoms including fever. The study's authors estimated that approximately 24 people would develop Guillain-Barre for every 100,000 people infected with Zika virus.
"Although it is unknown whether attack rates of Zika virus epidemics will be as high in affected regions in Latin America than in the Pacific Islands, high numbers of cases of Guillain-Barre syndrome might be expected in the coming months as the result of this association," said lead author Arnaud Fontanet, of France's Institut Pasteur.