RESEARCH First Isolation of West Nile virus from a Patient with Encephalitis in the United States Cinnia Huang,* Brett Slater,* Robert Rudd,* Nandakishore Parchuri,† Rene Hull,* Michelle Dupuis,* and Alexander Hindenburg† West Nile virus (WNV) was isolated from a patient who developed encephalitis while undergoing treatment with CHOP (cyclophosphamide, hydroxydoxorubicin, vincristine [Oncovin], predisone) and rituximab for a non-Hodgkin B-cell lymphoma. Both standard reverse transcription–polymerase chain reaction (RT-PCR) and Taqman RT-PCR established the diagnosis of WNV infection from cerebrospinal fluid (CSF). Several whole blood samples and one serum sample underwent further testing. CSF and serum samples were negative for WNV antibody; however, all samples were positive by both RT-PCR assays. Infectious virus was recovered from a blood sample, and its identity was confirmed by using a WNV-specific immunofluo- rescence assay. The complete WNV genomes determined from CSF and from the virus isolate adapted from cell culture were the same. The results represent the first complete WNV genome sequence obtained directly from human CSF and the first time that infectious WNV has been recovered from a patient with encephalitis in North America. W member of the Japanese encephalitis virus serocomplex est Nile virus (WNV), an arthropod-borne virus, is a of the genus Flavivirus, family Flaviviridae (1), discovered in Uganda in 1937 (2). Although WNV infections are usually mild or asymptomatic, in some instances, a severe and fatal encephalitis is produced, typically in the elderly (3). This virus was first recognized in the Western Hemisphere in an outbreak in New York in 1999 (4). As of October 2, 2002, a total of 2.671 cases of human illness in the United States have been reported to the Centers for Disease Control and Prevention (CDC). Although WNV has been recovered from mosquitoes, birds, and horses, no isolations from humans have been reported in the Western Hemisphere. Thus, all prior data regarding the virus responsible for human illness in North America have come from nucleic acid sequencing of the viral genome in either cerebrospinal fluid (CSF) or brain tissue. We describe the first isolation of WNV from a human case-patient associated with the U.S. outbreak. Because the virus was also directly detected by reverse transcription–polymerase chain reaction (RT-PCR) in specimens from the same patient, we were able to compare the entire genomic sequence of the directly detected virus with that of the cell-culture isolate. Case Report The patient was a 70-year-old woman, who has been diag- nosed with intermediate-grade, CD 20-positive, B-cell non- Hodgkin lymphoma, involving a left intraparotid lymph node. Staging workup demonstrated stage 1-A disease. Treatment plans for the patient included three courses of CHOP (cyclo- *Wadsworth Center, New York State Department of Health, Albany, New York, USA; and †Winthrop University Hospital, Mineola, New York, USA phosphamide, hydroxydoxorubicin, vincristine [Oncovin], and predisone) chemotherapy plus rituximab (chimeric CD 20 monoclonal antibody), to be followed by involved field radia- tion. After the first cycle of chemotherapy in July 2001, neu- tropenia developed and the patient was treated with granulocyte colony stimulating factor (GCSF) following both the second and third cycles of chemotherapy. The third cycle of chemotherapy was administered on September 11, 2001. Four days later, she was treated with oral levofloxacin for low- grade fever. On day 7 after chemotherapy, she was admitted to the hospital with fever, cough, chills, rhinorrhea, joint aches, decreased appetite, lethargy, and lightheadedness. She had no recollection of any ill contacts or insect bites. She was a resi- dent of southern Nassau County, New York, and did not have a history of travel. Physical examination was within normal lim- its. The patient was neutropenic; G-CSF was continued, and she was given cefipime and gentamicin. One day after admis- sion, she continued to have fever and experienced mild head- aches that responded to acetaminophen. Urine cultures showed penicillin-sensitive enterococci, and blood cultures were nega- tive. Two days after admission, the patient continued to have fever, headaches, and dizziness. A computed tomography (CT) scan of the brain revealed no acute cerebral processes. On the 3rd day after admission, the patient was noted to be confused. Further deterioration of mental status was noted, with incom- prehensible speech, but she was able to follow commands. Arterial blood-gas analysis showed an acute respiratory acido- sis pattern, and the patient was subsequently intubated and transferred to the intensive care unit. The patient had a hypotensive episode secondary to atrial flutter, which required cardioversion for stabilization. Ceftriaxone and ampicillin were added to the antibiotic coverage, and antifungal treatment was also initiated with lipid complex amphotericin B. After Emerging Infectious Diseases • Vol. 8, No. 12, December 2002 1367