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West Nile Virus Activity --- United States, October 10--16, 2002, and Update on West Nile Virus Infections in Recipients of Blood Transfusions

This report summarizes West Nile virus (WNV) surveillance data reported to CDC through ArboNET and by states and other jurisdictions as of 8 a.m. Mountain Daylight Time, October 16, 2002.

WNV Surveillance

During October 10--16, a total of 256 laboratory-positive human cases of WNV-associated illness were reported from Indiana (n=47), Nebraska (n=34), Michigan (n=32), Ohio (n=28), Illinois (n=21), Missouri (n=11), Pennsylvania (n=10), the District of Columbia (n=seven), Iowa (n=six), Kansas (n=six), Kentucky (n=six), Louisiana (n=six), Texas (n=six), Maryland (n=five), Georgia (n=four), South Dakota (n=four), Tennessee (n=four), Mississippi (n=three), New York (n=three), Virginia (n=three), Florida (n=two), Massachusetts (n=two), Minnesota (n=two), Connecticut (n=one), New Jersey (n=one), Vermont (n=one), and Wyoming (n=one). During this reporting period, Kansas, Vermont, and Wyoming reported their first human cases of WNV infection. During the same period, WNV infections were reported in 218 dead crows and 97 other dead birds. A total of 1,135 veterinary cases (1,026 equine and one other species) and 424 WNV-positive mosquito pools were reported.

During 2002, a total of 3,052 human cases with laboratory evidence of recent WNV infection have been reported from Illinois (n=675), Michigan (n=433), Ohio (n=341), Louisiana (n=299), Indiana (n=204), Mississippi (n=171), Missouri (n=149), Nebraska (n=114), Texas (n=107), New York (n=63), Kentucky (n=50), Pennsylvania (n=47), Tennessee (n=44), Alabama (n=39), Iowa (n=39), South Dakota (n=37), Minnesota (n=33), Wisconsin (n=28), Georgia (n=23), Virginia (n=23), Maryland (n=19), Massachusetts (n=19), North Dakota (n=15), the District of Columbia (n=13), Connecticut (n=12), Florida (n=12), Arkansas (n=11), New Jersey (n=eight), Kansas (n=six), Colorado (n=five), Oklahoma (n=four), North Carolina (n=two), West Virginia (n=two), California (n=one), Rhode Island (n=one), South Carolina (n=one), Vermont (n=one), and Wyoming (n=one) (Figure). Among the 2,661 patients for whom data were available, the median age was 56 years (range: 1 month--99 years); 1,416 (54%) were male, and the dates of illness onset ranged from June 10 to October 6. A total of 153 human deaths have been reported. The median age of decedents was 79 years (range: 27--99 years); 93 (61%) deaths were among men. In addition, 6,289 dead crows and 4,611 other dead birds with WNV infection were reported from 42 states and the District of Columbia; 6,427 WNV infections in mammals (6,418 equines, three canines, and six other species) have been reported from 35 states (Alabama, Arkansas, Colorado, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Vermont, Virginia, Wisconsin, and Wyoming). During 2002, WNV seroconversions have been reported in 342 sentinel chicken flocks from Florida, Iowa, Nebraska, Pennsylvania, and New York City; 4,434 WNV-positive mosquito pools have been reported from 26 states (Alabama, Arkansas, Connecticut, Delaware, Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Massachusetts, Mississippi, Missouri, Nebraska, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, South Dakota, Texas, Vermont, and Virginia), New York City, and the District of Columbia.

Additional information about WNV activity is available from CDC at and

WNV Infections in Recipients of Blood Tranfusions

CDC, the Food and Drug Administration, and the Health Resources and Services Administration, in collaboration with blood collection agencies and state and local health departments, continue to investigate West Nile virus (WNV) infections in recipients of blood transfusion. During August 28--October 16, CDC received reports from 14 states of 25 patients with West Nile meningoencephalitis (WNME) and four with other WNV-associated illnesses diagnosed after receiving blood components in the month before illness onset. All 29 of these patients resided in areas with high levels of WNV activity. CDC has been notified of one additional case, but demographic and clinical information is pending. Investigations are ongoing to determine whether transfusion was the source of WNV transmission. To date, four investigations provide evidence that WNV can be transmitted through blood transfusion.

Of the 29 cases, 14 (48%) were reported since October 1. Of the 24 patients for whom an illness onset date was specified, illness began in July (two patients), August (eight), September (13), and October (one); one additional patient, an organ donor, had West Nile viremia at the time of organ recovery in late July following receipt of multiple blood transfusions (1). Among these patients, the reason for hospitalization or the underlying conditions included a surgical procedure or obstetric delivery (eight); solid organ transplantation (four patients who received an organ from different donors who did not have evidence of WNV infection at the time of organ recovery); hematologic conditions (including myelodysplasia [three patients], acute myelogenous leukemia [five], acute lymphocytic leukemia [one], non-Hodgkin's lymphoma [one], thrombotic thrombocytopenic purpura [one]); and other medical conditions (six patients). These 29 patients received blood components from a median of 17 donors (range: two--185 donors). Among nine patients who died, WNME was the probable cause of death.

Among the four cases that provided evidence that WNV can be transmitted through blood transfusion, two patients developed confirmed WNME after receiving different blood components derived from a single blood donation that was subsequently found to have evidence of WNV (2). In follow-up testing, this donor seroconverted and developed WNV IgM antibody. In another case, WNV was isolated from a withdrawn unit of frozen plasma from the suspected donation, indicating that the virus can survive in some blood components (1). The donor of this plasma subsequently developed an acute febrile illness and seroconverted following the suspect collection. In a fourth case, a patient who had been hospitalized for 65 days developed WNME after receiving a component derived from a suspected donation that contained WNV RNA. Follow-up found that the donor had developed a febrile illness compatible with WNV-associated fever within days of the suspect donation; serology testing is pending.

Cases of WNV infection in patients who have received blood transfusions within the 4 weeks preceding illness onset should be reported to CDC through state and local public health authorities. Serum or tissue samples should be retained for later studies. In addition, cases of WNV infection in persons with illness onset within 2 weeks after blood donation should be reported. Prompt reporting of these cases will facilitate withdrawal of potentially infectious blood components.

Additional information about WNV activity is available from CDC at and


  1. CDC. Update: investigations of West Nile virus infections in recipients of organ transplantation and blood transfusion. MMWR 2002;51:833--6.
  2. CDC. Update: investigation of West Nile virus infections in recipients of organ transplantation and blood transfusion---Michigan, 2002. MMWR 2002;51:879.


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