West Nile Virus Infection in Belgian Traveler Returning from Greece - Vol. 19 No. 4 - April 2013 - Emerging Infectious Disease journal - CDC
Volume 19, Number 4—April 2013
Letter
West Nile Virus Infection in Belgian Traveler Returning from Greece
Article Contents
To the Editor: West Nile virus (WNV) is an arthropod-borne virus that is transmitted to humans by mosquitos, primarily of the genus Culex. Most human infections are asymptomatic. Clinical symptoms occur in ≈20% of case-patients and include fever, headache, and myalgia; <1 a="" develop="" disease="" href="http://wwwnc.cdc.gov/eid/article/19/4/12-1594_article.htm#r1" infections="" into="" neuroinvasive="" of="" severe="" title="1" wnv="">11>
Clinical diagnosis may be difficult because WNV infections resemble other (arbo)viral diseases. Laboratory diagnosis relies primarily on serologic testing. Reverse transcription PCR (RT-PCR) can be used to detect viral RNA during the acute phase of the disease, but its use is hampered by the patient’s low-level and transient viremia (1).
We here describe a confirmed case of WNV encephalitis imported by a traveler returning from Greece. A 73-year-old Belgian woman, who had a medical history of lymphoma, traveled to Kavala city (Macedonia, Greece). On August 14, 2012, she sought treatment at the Kavala General Hospital with a 6-day history of fever, headache, malaise, nausea, confusion, decline of consciousness, and neck stiffness. Results of laboratory testing on admission demonstrated an increased leukocyte count (9,670/µL; 80% neutrophils) and lactate dehydrogenase level (522 IU/L), a low C-reactive protein level (0.7 mg/dL), and hyponatremia (131 mEq/L). Cerebrospinal fluid (CSF) testing showed 90 cells/µL (79% lymphocytes) and glucose and protein levels of 72 and 100.9 mg/dL, respectively. Serum obtained on August 15 was sent to the national reference laboratory at Aristotle University (Thessaloniki, Greece), and IgM against WNV was detected by ELISA (WNV IgM Capture DxSelect and IgG DxSelect; Focus Diagnostics, Cypress, CA, USA). IgG was absent. On the second day of hospitalization, the patient exhibited seizures (speech arrest); she was given phenytoin (1/2 amp 3×/day intravenously). On August 18, the patient was transferred to a private hospital. Further treatment included intravenous fluid, antipyretics, antimicrobial drugs, mannitol, and oxygen. On August 30, she was returned by plane to Belgium.
CSF obtained 26 days after symptom onset and serum obtained 29 days after symptom onset were sent to the Institute of Tropical Medicine (Antwerp, Belgium) because of its function as a national reference center for Belgium. IgM and IgG against WNV were detected in both samples by ELISA (Focus Diagnostics) (Table). Immunofluorescence assays on serum revealed IgM against WNV only and IgG against West Nile, dengue, yellow fever, and Japanese encephalitis viruses, with the strongest reaction against WNV (Flavivirus Mosaic 1; Euroimmun, Lübeck, Germany). Real-time RT-PCR (adapted from [5]) on the serum demonstrated a weak positive signal. Repeated RNA extraction and RT-PCR were confirmative (Table). Sequencing of the RT-PCR product confirmed the detection of WNV. Although the product was short (116 bp), it was highly suggestive of WNV, lineage 2. Flemish regional authority in Belgium, national authorities (both in Belgium and Greece), and European health authorities were notified of the imported case of WNV encephalitis. According to the case definition of the European Center for Disease Prevention and Control, Stockholm, Sweden, the patient met the laboratory criteria of having a confirmed case.
To date, autochthonous WNV infections have not been reported in Belgium, although the presence of the mosquito vector provides a potential risk for transmission (6). This WNV infection was acquired in Greece (a leading travel destination for tourists from Belgium), specifically in the Kavala region, which was highly affected by WNV in 2012. The lineage responsible for the WNV encephalitis was identified as lineage 2, the currently circulating strain in Greece (7). Our report highlights the need for physicians and laboratory staff to be aware of imported WNV infections originating from southeastern Europe, especially Greece and its neighboring countries, where recent and recurrent outbreaks have occurred (3,4).
Special attention should be given to immunosuppressed and elderly patients who are at higher risk of acquiring neuroinvasive disease. The 73-year-old patient described here was unconscious when she arrived in Belgium. After a short period of relative improvement (more reactive and cooperative), her condition deteriorated, and she died on November 23, 2012. The detection of viral RNA 29 days after symptom onset was surprising but might be explained by the immunocompromised status of the patient. Several studies have reported persistent WNV RNA for 30 days, 77 days, and even years after the symptom onset in serum, CSF, and urine, respectively (8–10), and a prolonged period of viremia in immunocompromised patients (9).
Acknowledgment
We thank Kathy Demeulemeester, Elke Gintelenberg, and the laboratory staff of the serology unit of the Central Laboratory for Clinical Biology, Antwerp, for their excellent technical support.
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Suggested citation for this article: Cnops L, Papa A, Lagra F, Weyers P, Meersman K, Patsouros N, et al. West Nile virus infection in Belgian traveler returning from Greece [letter]. Emerg Infect Dis [Internet]. 2013 Apr [date cited]. http://dx.doi.org/10.3201/eid1904.121594
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