Serum samples from 446 randomly selected persons belonging to different age groups and locations in Nigeria were tested for the presence of WSLV IgM using the flavivirus haemagglutination-inhibition (HI) test adopted to the solid-phase immunosorbent technique (SPIT). 61 (14%) persons had IgM to WSLV only, while 9 (2%) persons had heterologous IgM to WSLV and two other flaviviruses, namely yellow fever and Uganda S viruses. There was a high prevalence of IgM in people of younger age groups than those in older groups. The majority of the IgM positive sera (67 (96%) of the 70 positive sera reacted to high titres (>21:80). With the conventional HI tests, 314 (70%) of the total sera tested had HI antibodies to one or more flaviviruses (yellow fever, West Nile, Potiskum, Zika and Uganda S) out of which 305/314 (97%) had antibodies to 3 or more flaviviruses used in the tests. Although SPIT may not be as sensitive as the conventional HI test, it was found to be more specific and could be adopted for the detection of early WSLV infections in flavivirus hyperendemic environments.