Influenza Illness among Case-Patients Hospitalized for Suspected Dengue, El Salvador, 2012

<div><p>We estimate the proportion of patients hospitalized for suspected dengue that tested positive for influenza virus in El Salvador during the 2012 influenza season. We tested specimens from 321 hospitalized patients: 198 patients with SARI and 123 patients with suspected dengue. Among 121 hospitalized suspected dengue (two co-infected excluded) patients, 28% tested positive for dengue and 19% positive for influenza; among 35 with suspected dengue and respiratory symptoms, 14% were positive for dengue and 39% positive for influenza. One percent presented co-infection between influenza and dengue. Clinicians should consider the diagnosis of influenza among patients with suspected dengue during the influenza season.</p></div

Laboratory test results for influenza and dengue viruses in patients with suspected dengue or severe acute respiratory illness (SARI) at hospital admission, 4 hospitals in El Salvador, during July 1 through September 30, 2012.

<p>Laboratory test results for influenza and dengue viruses in patients with suspected dengue or severe acute respiratory illness (SARI) at hospital admission, 4 hospitals in El Salvador, during July 1 through September 30, 2012.</p

Respiratory symptoms among hospitalized patients with suspected dengue, 4 hospitals in El Salvador, during July 1 through September 30, 2012.

<p>Respiratory symptoms among hospitalized patients with suspected dengue, 4 hospitals in El Salvador, during July 1 through September 30, 2012.</p

Meteorological parameters, influenza positive proportion and regression output for the study areas.

<p>In the last row, black curves are the observed data; grey shades indicate the 95% confidence interval; red curves are modeled results; and blue curves are the prospectively estimated influenza activity using actual meteorological data and regression models trained with influenza data from previous years. OR is the odds ratio from the regression for the meteorological parameters, and CI is the associated 95% Confidence Interval.</p

Change in influenza positive proportion when the indicated meteorological variable was increased by 1 standard deviation (temperature 2.74°C, specific humidity 2.61 g/kg, rainfall 6.48 mm/day).

<p>Change in influenza positive proportion when the indicated meteorological variable was increased by 1 standard deviation (temperature 2.74°C, specific humidity 2.61 g/kg, rainfall 6.48 mm/day).</p

Multivariable analysis of meteorological factors associated with influenza positivity.

<p>Bold font indicates a statistically significant variable (<i>p-value</i><0.05). RMSE is the Root Mean Squared Error and Corr. Coeff is the correlation coefficient between the observation and estimated influenza positive proportion in 2013.</p><p>The models were adjusted for: potentially confounding variables (RSV, parainfluenza and adeno viruses), previous weeks' influenza positivity, seasonality and other possible nonlinear relationships (modeled as a polynomial function, up to degree of 3, of the week number).</p

Study areas.

<p>Departments or provinces included in the study. Adjacent departments in Guatemala and El Salvador were combined in the analysis: Western departments in Guatemala (1,2), Central departments in Guatemala (3,4) and West-central departments in El Salvador (5–8).</p

Percent change in model deviance.

<p>Change in deviance between the full model (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0100659#pone-0100659-t002" target="_blank">Table 2</a>) and the model with the indicated meteorological variable removed.</p