IFNG and Lassa fever: T cell responses among LF survivors (known LF convalescent patients without LF symptoms or a positive LASV polymerase chain reaction [PCR] test at the time of sample collection) and their contacts (exposed to LASV but without a history of LF symptoms or a positive LASV polymerase chain reaction [PCR] test at the time of sample collection- these are people who may have managed or provided care to LF acute or convalescent patients such as family members, clinicians, nurses etc.)were evaluated using direct ex vivo interferon gamma (IFNγ) T cell ELISpot.