An office-based prospective study of deafness in mumps.

BACKGROUND Deafness is a rare but important complication of mumps virus infection. Its incidence has been estimated at 0.5 to 5.0 per 100,000 cases of mumps, but recent reports from Japan, where mumps is endemic, suggest that the incidence might be higher. OBJECTIVE Prospective office-based study to determine the incidence of hearing loss in children with mumps. METHODS Forty pediatric practices participated in this survey. The study population consisted of patients < or =20 years old with mumps seen between January 2004 and December 2006. Clinical diagnosis of mumps was made by experienced pediatricians. Among those from whom written consent was obtained, parents were asked to conduct hearing screening tests by rubbing fingers near the ears twice daily for 2 weeks. Patients suspected with hearing loss were further examined by an otolaryngologist. RESULTS Among 7400 children who underwent hearing ability assessment after clinical onset of mumps, 7 had confirmed hearing loss; none had been previously vaccinated against mumps. In all cases, hearing loss was unilateral but severe and did not improve over time. CONCLUSIONS The incidence of hearing loss in children due to mumps was 7/7400 (approximately 1/1000 cases), which is higher than previously suggested. Prevention of deafness is another important reason for assuring universal immunization against mumps.