Lassa fever-induced sensorineural hearing loss: A neglected public health and social burden.

Although an association between Lassa fever (LF) and sudden-onset sensorineural hearing loss (SNHL) was confirmed clinically in 1990, the prevalence of LF-induced SNHL in endemic countries is still underestimated. LF, a viral hemorrhagic fever disease caused by Lassa virus (LASV), is endemic in West Africa, causing an estimated 500,000 cases and 5,000 deaths per year. Sudden-onset SNHL, one complication of LF, occurs in approximately one-third of survivors and constitutes a neglected public health and social burden. In the endemic countries, where access to hearing aids is limited, SNHL results in a decline of the quality of life for those affected. In addition, hearing loss costs Nigeria approximately 43 million dollars per year. The epidemiology of LF-induced SNHL has not been characterized well. The complication of LF induced by SNHL is also an important consideration for vaccine development and treatments. However, research into the mechanism has been hindered by the lack of autopsy samples and relevant small animal models. Recently, the first animal model that mimics the symptoms of SNHL associated with LF was developed. Preliminary data from the new animal model as well as the clinical case studies support the mechanism of immune-mediated injury that causes SNHL in LF patients. This article summarizes clinical findings of hearing loss in LF patients highlighting the association between LASV infection and SNHL as well as the potential mechanism(s) for LF-induced SNHL. Further research is necessary to identify the mechanism and the epidemiology of LF-induced SNHL.