Scientists discover a link between the mosquito-borne disease and a rare disorder that can lead to nerve damage and paralysis.
New research has confirmed the Zika virus can trigger the paralysis condition Guillain-Barre.
Sourced media revealed two weeks ago that Colombian doctors had found the virus in five patients with the neurological condition.
Now scientists at the Institut Pasteur in France have analysed a Zika outbreak in French Polynesia in 2013-14 and also found patients have increased risk of Guillain-Barre (GBS) around six days later.
The syndrome is caused by an abnormal immune response to an infection, which results in nerve damage and paralysis.
In 20-30% of patients the breathing muscles stop working and 5% die despite intensive care.
Professor Arnaud Fontanet, the lead researcher, told Sky News that the condition could be a massive challenge for countries with limited healthcare in south and central America.
"In our study 38% of the patients had to be hospitalised in intensive care for respiratory assistance," he said.
"We need to urge countries to get ready in areas where the epidemic is reaching its peak to be able - as much as they can - to accommodate those patients in intensive care units."
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The researchers calculate in The Lancet medical journal that 24 in every 100,000 people infected with Zika will go on to develop Guillain-Barre.
The finding suggests hundreds of people in South and Central America are likely to become paralysed as the pandemic unfolds, with recovery uncertain.
If the virus has mutated, or the Latin American population is more susceptible than the Polynesians to severe effects of the infection, the numbers could be even higher.
The health minister of Colombia has warned hospitals to prepare for 1,500 cases of Guillain-Barre over the coming months.
Sourced news filmed in two hospitals in Cali, where researchers found evidence that the Zika virus can linger long after the symptoms have gone - and that could trigger GBS.
Dr Andres Zea, a neurologist at the hospital, said: "In my mind it is related to Zika.
"It is terrible. It's a mosquito. Only one bite and 15 days later, 20 days later, you are going to be in intensive care. These patients have families."
One of Dr Zea's patients had suffered a cardiac arrest and brain damage as a result of nerve damage caused by Guillain Barre.
Another, Sandra Tamayo, was unable to move her facial muscles because of GBS. She couldn't blink and struggled to move her mouth.
"The situation is terrible, really terrible," she said. "I can't express anything. If I am smiling inside I can't express it. It's like wearing a mask."