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Letter
Imported West Nile Virus Infection
in Europe
P.E. Charles,* H. Zeller,† B. Bonnotte,* A.L. Decasimacker,* J.B.
Bour,* P. Chavanet,* and B. Lorcerie*
*Dijon University Hospital, Dijon, France; and †Institut Pasteur, Lyon,
France
Suggested citation for this article: Charles
PE, Zeller H, Bonnotte B, Decasimacker AL, Bour JB, Chavanet P, et al.
Imported West Nile virus infection in Europe. Emerg Infect Dis [serial
online] 2003 Jun [date cited]. Available from: URL: http://www.cdc.gov/ncidod/EID/vol9no6/02-0723.htm
To the Editor: We report the case of an 82-year-old man, recently
arrived in France from Atlanta, Georgia, USA, who had chills and fever
in late August 2002. He left Atlanta on August 26, 2002, and spent a week
in Paris before he reached Burgundy. On day 9, after his arrival in the
town of Dijon, he had chills and fever (40°C), weakness, malaise, diarrhea,
and headache. He was then admitted to Dijon University Hospital. Physical
examination indicated hyporeflexia, mild changes in mental status, and
no neck stiffness. No lumbar puncture was performed.
Laboratory findings included the following: hyponatremia, 129 mmol/L
(normal range 135–145 mmol/L); C-reactive protein, 13 mg/L (normal <3
mg/L); lymphocyte count, 500 cells/mm3 (normal range, 1,000–4,000
cells/mm3); positive antinuclear antibodies, 1/160 (homogenous);
and positive anti-DNA antibodies, 76 Word Health Organization (WHO) U
(normal <39 WHO U). Blood and urine samples remained sterile. Results
of the chest roentgenogram and electrocardiogram were normal.
Serum immunoglobulin (Ig) M antibodies to West Nile virus (WNV) were
detected by using antibody-capture enzyme-linked immunosorbent assay (ELISA);
IgG antibodies were not found by ELISA. A second serologic test performed
2 weeks later in the United States also showed specific IgM antibodies
to WNV. The diagnosis of WNV infection was thus established. Four days
after admission, the patient no longer had a fever, and his mental status
was normal.
WNV infection is a potentially lethal mosquito-borne infection (1).
Since 1994, many notable outbreaks have occurred (2-4).
The virus emerged in New York, New York, USA, in 1999, and WNV infection
is likely to become enzootic in the United States (5).
In 2002, WNV was reported in 43 states, and human cases were reported
in 33 states (6). The first human case in Georgia was
described in 2001.
We report the first imported case of WNV infection in Europe, on the
basis of criteria established by the Centers for Disease Control and Prevention.
WNV infection was suspected because our patient arrived from an area where
WNV is epidemic during the late summer. Clinical findings were similar
to those described in previous cases (5). Encephalitis
was suspected because the patient showed a reversible alteration of mental
status and headache. Although hyponatremia and lymphocytopenia have previously
been reported in cases of WNV infection, positive anti-DNA antibodies
is a finding of particular interest. However, the mild elevation of antibody
titers is common in other viral infections, especially in those caused
by members of the Flaviviridae family such as hepatitis C virus
(7). Although the prognosis of WNV infection is generally
poor in elderly patients, our patient had a good outcome (5,8).
In conclusion, physicians in western Europe should be aware of the risk
of WNV infection among travelers from a disease-endemic area such as the
United States, especially during late summer. Specific antibody detection
tests should be performed in such patients with unexplained fever, particularly
when they show evidence of neurologic disease. Suspected and confirmed
cases can then be quickly reported to health departments, leading to an
improvement in the public health response. However, imported cases like
this one are not likely to contribute to the spread of WNV infection in
Europe. Indeed, human viremia levels seem too low and of insufficient
duration to allow the infection of competent mosquito vectors and the
subsequent transmission of the virus to other hosts, such as horses or
humans (9).
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