Primary Versus Nonprimary West Nile Virus Infection: A Cohort Study.
BACKGROUND
Since 2001, we have observed patients with a clinical picture consistent with West Nile virus (WNV) infection, which was defined as nonprimary infection (NPI) owing to the presence of highly elevated serum immunoglobulin G antibody titers with a high avidity index (≥ 55%), absent or low titers of serum and cerebrospinal fluid (CSF) immunoglobulin M, and occasionally positive results of WNV-specific real-time reverse-transcription polymerase chain reaction analysis of CSF and/or blood specimens.


METHODS
We investigated 124 patients with a diagnosis of primary WNV infection (PI) or NPI during 2005-2007 at Sheba Medical Center (Tel-Hashomer, Israel). Logistic regression was used to evaluate the association of variables with PI and NPI and with in-hospital mortality.


RESULTS
A total of 68 and 50 patients with PI and NPI, respectively were included; 6 patients had incomplete data. In multivariate models, NPI was significantly associated with underlying psychiatric disorders (adjusted odds ratio [aOR], 13.73; 95% confidence interval [CI], 2.28-82.56; P = .004), hospitalization during winter and spring (aOR, 8.82; 95% CI, 1.59-48.87; P = .013), and fever (aOR, 0.61; 95% CI, .39-.95; P = .031). In-hospital mortality was significantly associated with NPI (aOR, 3.86; 95% CI, 1.12-13.28; P = .032) and a higher Charlson comorbidity index (aOR, 1.37; 95% CI, 1.03-1.83; P = .032).


CONCLUSIONS
The possibility that NPI may be an emerging clinical entity with a high mortality rate must be considered seriously.
Infectious Diseases Unit Sackler School of medicine, Tel Aviv University, Israel.
Galia
G
Rahav
Infectious Diseases Unit.
Michal
M
Hagin
Infectious Diseases Unit Sackler School of medicine, Tel Aviv University, Israel.
Yasmin
Y
Maor
Department of Neurology.
Gilad
G
Yahalom
Central Virology Laboratory, Ministry of Health, Chaim Sheba Medical Center, Tel Hashomer Sackler School of medicine, Tel Aviv University, Israel.
Musa
M
Hindiyeh
Central Virology Laboratory, Ministry of Health, Chaim Sheba Medical Center, Tel Hashomer Sackler School of medicine, Tel Aviv University, Israel.
Ella
E
Mendelson
Central Virology Laboratory, Ministry of Health, Chaim Sheba Medical Center, Tel Hashomer.
Hanna
H
Bin
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007557:Israel / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors; D012621:Seasons; D014901:West Nile Fever / Q000453:epidemiology / Q000635:transmission* / Q000821:virology; D014902:West Nile virus; D055815:Young Adult
West Nile virus; nonprimary infection; primary infection