West Nile virus activity--United States, January 1-September 12, 2006

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, September 12, 2006. A total of 36 states and the District of Columbia had reported 1,634 cases of human WNV illness to CDC. A total of 921 (57%) cases for which such data were available occurred in males; median age of patients was 51 years (range: 3 months-95 years). Dates of illness onset ranged from January 6 to September 10; a total of 52 cases were fatal.     

West Nile virus activity--United States, January 1-August 15, 2006

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, August 15, 2006. A total of 26 states had reported 388 cases of human WNV illness to CDC. A total of 214 (56%) cases for which such data were available occurred in males; median age of patients was 49 years (range: 2-91 years). Dates of illness onset ranged from January 6 to August 10; a total of 13 cases were fatal. A total of 68 presumptive West Nile viremic blood donors (PVDs) have been reported to ArboNET during 2006. Of these, 20 were reported from Nebraska; 18 were reported from Texas; five were reported from California; four were reported from Utah; three each were reported from Oklahoma and South Dakota; two each were reported from Idaho, Iowa, Kentucky, and Mississippi; and one each was reported from Arizona, Colorado, Minnesota, Nevada, North Dakota, Wisconsin, and Wyoming. Of the 68 PVDs, 10 persons (median age: 43 years [range: 18-59 years]) subsequently had West Nile fever.     

West Nile virus activity--United States, January 1-July 18, 2006

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, July 18, 2006. A total of 10 states had reported 15 cases of human WNV illness to CDC. Nine (60%) cases for which such data were available occurred in males; median age of patients was 50 years (range: 9-89 years). Date of illness onset ranged from January 6 to July 8; no deaths were reported.     

West Nile virus activity--United States, January 1-October 10, 2006

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, October 10, 2006. A total of 41 states and the District of Columbia had reported 3,135 cases of human WNV illness to CDC. A total of 1,717 (55%) cases for which such data were available occurred in males; median age of patients was 50 years (range: 3 months-99 years). Dates of illness onset ranged from January 6 to September 25; a total of 97 cases were fatal.     

Update: West Nile virus activity--United States, 2005

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, August 30, 2005.     

Update: West Nile virus activity--United States, 2005

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, September 13, 2005.     

Update: West Nile virus activity--United States, 2005

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Daylight Time, October 25, 2005.     

Update: West Nile virus activity--United States, 2005

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Standard Time, November 1, 2005.     

West Nile virus activity--United States, 2007

West Nile virus (WNV) is the leading cause of arboviral encephalitis in the United States. Originally identified in Africa in 1937, WNV was first detected in the western hemisphere in 1999 in New York City. Since then, WNV has caused seasonal epidemics of febrile illness and neurologic disease in the United States. This report summarizes national WNV surveillance data for 2007. WNV transmission to humans or animals expanded into 19 counties that had not reported transmission previously and recurred in 1,148 counties where transmission had been reported in previous years. A total of 1,227 cases of WNV neuroinvasive disease (WNND) and 117 deaths were reported. These findings highlight the need for ongoing surveillance, mosquito control, promotion of personal protection from mosquito bites, and research into additional prevention strategies, including a WNV human vaccine.     

West Nile virus activity--United States, 2006

West Nile virus (WNV) is the leading cause of arboviral encephalitis in the United States. Originally discovered in Africa in 1937, WNV was first detected in the western hemisphere in 1999 in New York City. Since then, WNV has caused seasonal epidemics of febrile illness and severe neurologic disease in the United States. This report summarizes provisional WNV surveillance data for 2006 reported to CDC as of April 3, 2007. During 2006, WNV transmission to humans or animals expanded into 52 counties that had not previously reported transmission and recurred in 1,350 counties where transmission had been reported in previous years. In addition, 1,491 cases of WNV neuroinvasive disease (WNND) were reported in the United States during this period, amounting to a 14% increase from 2005 and the largest number reported since 2003. On the basis of extrapolations from past serosurveys, an estimated 41,750 cases of non-neuroinvasive WNV disease occurred in 2006; of these cases, 2,770 were reported. These findings highlight the need for ongoing surveillance, mosquito control, promotion of personal protection from mosquito bites, and research into additional prevention strategies.     

West Nile virus activity--United States, September 25-October 1, 2003

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m., Mountain Daylight Time, October 1, 2003.     

West nile virus activity--United States, January 1-November 7, 2006

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET as of 3 a.m. Mountain Standard Time, November 7, 2006. A total of 41 states and the District of Columbia had reported 3,830 cases of human WNV illness to CDC.     

West Nile Virus activity--United States, 2001

In 2001, West Nile virus (WNV) activity was reported from 359 counties in 27 states and the District of Columbia (DC) to ArboNET, a web-based, surveillance data network maintained by 54 state and local public health agencies and CDC. This activity represented a marked increase from 2000, when WNV activity was reported from 138 counties in 12 states and DC. This report summarizes surveillance data for 2001, which indicate that 66 human illnesses were reported from 10 states and that widespread WNV activity in birds, horses, and mosquitoes extended into the midwestern United States and several southern states unaffected previously. The findings in this report underscore the need for public education, increased WNV surveillance aimed at early viral detection, and sustained, integrated mosquito-control activities.     

West Nile virus activity--United States, July 21-27, 2004

During July 21-27, a total of 83 cases of human West Nile virus (WNV) illness were reported from 13 states (Alabama, Arizona, Arkansas, California, Colorado, Florida, Illinois, Iowa, Missouri, New Mexico, Ohio, Pennsylvania, and South Dakota).