tokens: Age ( odds ratio [ OR ] , 3.73 ; 95 % CI , 1.87 to 7.45 ; p<0.001 ) and level of education ( no formal education : OR , 4.31 ; 95 % CI , 1.08 to 17.2 ; p<0.05 ; primary : OR , 7.29 ; 95 % CI , 1.80 to 29.6 ; p<0.01 ) were significant risk factors for WNV IgM seropositivity in humans .