After an epidemic of West Nile (WN) virus neurologic infections in southeastern Romania in 1996, human and animal surveillance were established to monitor continued transmission of the virus. During 1997 and 1998, neurologic infections were diagnosed serologically as WN encephalitis in 12 of 322 patients in 19 southeastern districts and in 1 of 75 Bucharest patients. In addition, amid a countrywide epidemic of measles, the etiology of the febrile exanthem in 2 of 180 investigated cases was determined serologically to be WN fever; 1 case was complicated by hepatitis. Sentinel chickens placed in Bucharest seroconverted to WN virus during the summer months, indicating their potential value in monitoring transmission. The continued occurrence of sporadic WN infections in southeastern Romania in consecutive years after the 1996 epidemic is consistent with local enzootic transmission of the virus.