Causes them to spasm.
Dear Arvind,
virus or rabies (rhabodvirus) goes up into the termination of the synaptic button and alterates the exchange of electrolytes on the neuron membrane.
So, there are changes in membrane potentials and that results in spasms (automatic).
As deglutition is a reflex/reflection, drinking (also your saliva) activates these automatic spasms, as a terrible chain of contraction activation that can lead to choking.
Although it is rare in humans (common in animals), idrofobia is caused by the pre-activation of deglutition: in fact normally when someone sees water,there is an automatic reflection that is the start of the deglutition chain. So infected patients have fear of water because of this unconscious preactivation of deglutition, and take care: these spasms can lead to a choking because of the disfunction of glottis.