Early-onset sensorineural hearing loss in Lassa fever

Lassa fever (LF) is a viral hemorrhagic disease which affects one-fourth to two million people annually with the fatality rate of about 10,000. It is associated with sensorineural hearing loss (SNHL) usually at the convalescent stage. Recently, cases of SNHL at the acute phase have been reported. This study was done to further investigate the incidence and features of SNHL in acute phase of LF. It is a prospective case-control study of LF patients seen with acute SNHL conducted between July 2007 and April 2009 at Irrua Specialist Teaching Hospital Nigeria. The diagnosis of acute LF was based on the clinical features and detection of IgM antibodies and/or positive Lassa virus-specific reverse transcriptase-polymerase chain reaction using primers S36+ and LVS 339 while SNHL was diagnosed clinically and confirmed with PTA and speech discrimination tests. Patients with other acute febrile illnesses were used as control. Statistical analysis was done using SPSS version 11 and Fisher's exact test while level of significance was set at p < 0.05. Out of the 37 confirmed cases of LF, 5 (13.5%) and none (0%) of the control developed early-onset SNHL (p = 0.03). Forty percent of the cases studied had negative IgM. The audiograms showed involvement at all frequency groups with pure tone average 65-85 dB and the speech discrimination 20-40%. The overall case fatality rate was 27.0%, and for early SNHL cases 60.0% (p > 0.05). The incidence of SNHL in LF infection is about 13.5% and could be a reflection of a worse disease process. There is possibility of direct viral invasion aside immunological reaction as a causative mechanism.