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Under-recognition of dengue infection may lead to increased morbidity and mortality, whereas early detection is shown to help improve patient outcomes. Recent incidence and outbreak reports of dengue virus in the United States and other temperate regions where dengue was not typically seen have raised concerns regarding appropriate diagnosis and management by healthcare providers unfamiliar with the disease. This study aimed to describe self-reported clinical symptoms of dengue fever in a non-endemic cohort and to establish a clinically useful predictive algorithm based on presenting features that can assist in the early evaluation of potential dengue infection. Volunteers who experienced febrile illness while traveling in dengue-endemic countries were recruited for this study. History of illness and blood samples were collected at enrollment. Participants were classified as dengue naive or dengue exposed based on neutralizing antibody titers. Statistical analysis was performed to compare characteristics between the two groups. A regression model including joint/muscle/bone pain, rash, dyspnea, and rhinorrhea predicts dengue infection with 78% sensitivity, 63% specificity, 80% positive predictive value, and 61% negative predictive value. A decision tree model including joint/muscle/bone pain, dyspnea, and rash yields 77% sensitivity and 67% specificity. Diagnosis of dengue fever is challenging because of the nonspecific nature of clinical presentation. A sensitive predicting model can be helpful to triage suspected dengue infection in the non-endemic setting, but specificity requires additional testing including laboratory evaluation.

Background: The once-in-a-lifetime recommendation for vaccination against yellow fever virus (YFV) has been controversial, leading to increased scrutiny of the durability of immunity after 17D vaccination., Methods: This is a cross-sectional analysis of 17D vaccinees living in nonendemic Portland, Oregon. Neutralization assays were used to determine YFV immunity. The relationships between 17D immunity and vaccination history, demographics, and travel were evaluated using nominal logistic regression., Results: Seventy-one of 92 (77.2%) subjects were YFV seropositive (90 percent plaque reduction neutralization test ≥1:10) at all timepoints, and 24 of 38 (63.8%) were YFV seropositive at ≥10 years after single-dose vaccination. No relationship was found between YFV immunity and time in endemic countries, other flavivirus immunity, or demographics. Subjects were most likely to become seronegative between 3 and 12 years postvaccination (logistic regression, odds ratio [OR] = 1.75; 95% confidence interval [CI], 1.12-2.73). A comparison of our results and 4 previous studies of YFV nonendemic vaccinees found that overall, 79% (95% CI, 70%-86%) of vaccinees are likely to be seropositive ≥10 years postvaccination., Conclusions: These results suggest that 1 in 5 17D vaccinees will lack neutralizing antibodies at ~10 years postvaccination, and a booster vaccination should be considered for nonendemic vaccinees before travel to regions where there is a high risk of YFV transmission., (© The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)