West Nile virus surveillance in Romania: 1997-2000

In response to the 1996 West Nile (WN) fever epidemic that occurred in Buch arest and southeastern Romania, a surveillance program was established. The surveillance system detected 39 clinical human WN fever cases during the p eriod 1997-2000: 14 cases in 1997, 5 cases in 1998, 7 cases in 1999, and 13 cases in 2000. Thirty-eight of the 39 case-patients lived in the greater D anube Valley of southern Romania, and 1 case-patient resided in the distric t of Vaslui, located on the Moldavian plateau. The estimated annual case in cidence rate for the surveillance area during the period 1997-2000 was 0.95 cases per million residents. Thirty-four cases were serologically confirme d, and 5 cases were classified as probable. Twenty-four case-patients prese nted with clinical symptoms of meningitis (62%), 12 with meningoencephaliti s (31%), 1 with encephalitis (3%), and 2 with febrile exanthema (5%). Five of the 39 cases were fatal (13%). Fourteen case-patients resided in rural a reas, and 25 in urban and suburban areas, including 7 case-patients who res ided in Bucharest. The ages of case-patients ranged from 8 to 76 years with a median age of 45 years. Twenty-four case-patients were males and 15 were females. Dates of onset of illness occurred from May 24 through September 25, with 82% of onset dates occurring in August and September. Limited ento mological surveillance failed to detect WN virus. Retrospective sampling of domestic fowl in the vicinity of case-patient residences during the years 1997-2000 demonstrated seroprevalence rates of 7.8%-29%. Limited wild bird surveillance demonstrated seroprevalence rates of 5%-8%. The surveillance d ata suggest that WN virus persists focally for several years in poorly unde rstood transmission cycles after sporadic introductions or that WN virus is introduced into Romania at relatively high rates, and persists seasonally in small foci.