Scientists say they are on the verge of confirming that Zika is the cause of the paralysing condition Guillain-Barre.

Colombian researchers say they have detected the virus lingering in the blood of five patients with the syndrome.

Such persistent infection can trigger the chain reaction that leads the immune system to go rogue and attack the nerves, causing the paralysis.

With every additional case the cause becomes more certain, according to Dr Andreas Zea, a neurologist in Cali who is closely involved in the joint Colombian-American research project.

"In my mind it is related to Zika," he said.

"It is terrible. It’s a mosquito. Only one bite and 15, 20 days later you are going to be in intensive care. These patients have families".

45-year-old sugar cane worker Alix Mulato contracted Zika and then developed Guillain-Barre.

Now he is paralysed, brain damaged and beyond medical help.

His wife, Elizabeth Ramos, says he is lying under a net in intensive care.

"My husband was a very healthy man," she said.

"For our family it is a complete tragedy. We have been together a long time, with our sons. We don't understand. Why him? Why him?".

"The situation is terrible"

Sandra Tamayo, a patient in In Cali's University Hospital, developed Guillain-Barre shortly after contracting Zika.

Her face is paralysed, cannot blink and struggles to move her mouth.

She says she has not allowed her daughter to visit since being admitted two weeks ago for fear of frightening her.

"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".

The hospital would normally see a couple of Guillain-Barre cases a month. But that has doubled in the wake of the Zika epidemic.

And with Cali expecting another 20,000 patients with the virus over the next four months, doctors are making preparations for the numbers with Guillain-Barre to rise by 10 times.

"It will be difficult to get enough places in intensive care units for the people who will need it in the next months," Dr Zea warned.

He is also concerned that immunoglobulin, the antibody treatment derived from human blood donations, will be in short supply as demand increases across the region.

Eight countries in South and Central America have reported a rise in Guillain-Barre.

The World Health Organisation (WHO) has warned that if the link with Zika is confirmed, the human and social consequences will be staggering.