Research into a possible viral cause is mentioned on the IC-PBS website.
This is a Catalyst clip from 2013 about two medical scientists from Melbourne, Jason Roberts and Bruce Thorley, who have created 3D simulated models of viruses with supercomputers.
The benefit of these models is it allows researchers to study the behaviour of a virus in different environments, and to see how a virus responds to different drugs - showing sensitivities and resistances and predicting drug success. The models have been successful in revealing how a viral infection occurs. The researchers also discovered a completely new, never-before-seen virus from a paralysed child.
The hope back in 2013 was to create a ready-made toolkit for researchers and drug companies to allow them to test drugs and virus behaviour using the model.
This clip focuses on the polio virus, but it says they were also modelling other viruses
https://www.youtube.com/watch?v=gndl44IiZlc
This work is being carried out at the Victorian Infectious Diseases Reference Laboratory http://www.vidrl.org.au/