Virus causing sensori-neural hearing loss (unilateral SNHL)
Ans) b (Mumps) Ref Dhingra 4th edition p34-36Measles, mumps and cytomegalovirus are well documented to produce labryrinthitis which is common cause for acquired SNHL.Viruses usually reach the inner ear by blood stream affecting stria vascularis and then endolymph and organ of corti.Several other viruses, eg rubella, herpes zoster, herpes simplex, influenza, and Epstein - Barr vims are clinically known to cause deafness but direct proof of their invasion of labyrinth is lacking.There is another entity called sudden SNHL. In this condition SNHL will develop over a period of hours or few weeks. Mostly it will be unilateral. It may be accompanied by tinnitus or temporary spell of vertigo. Viral infections like mumps and herpes zoster are aetiological factors."Unilateral SNHL" was clearly given in the original question paperSo most probably mumps may be the right answer.
Rubella
Mumps
Herpes simplex
Epstein-Barr virus
Hearing Loss