Figure legends
Figure 1. Weekly reported virologically-confirmed influenza
cases, and all-cause and influenza-like-illness (ILI) specific absences
in Allegheny County, Pennsylvania, USA, during influenza seasons from
2007 to 2015 . Surveillance of influenza cases during each influenza
season in Allegheny County occurred from the 40th week of one year to
the 20th week of the following year (solid black lines). All-cause
absences were collected for the entire school year for each school
district, and data were restricted to their respective influenza
seasons. Nine school districts within Allegheny contributed to weekly
counts of all-cause absences. Additionally, all-cause and ILI-specific
absences were collected during independent influenza seasons for three
separate studies: 2007-2008 (PIPP study), 2012-2013 (SMART study), and
2015-2016 (SMART2 study). Absence surveillance data
were not collected during the 2008-2009 or 2009-2010 influenza seasons.
White space on the x-axis reflects periods when data were not collected
for this analysis, whereas black lines on the x-axis (in negative y
values) indicate time periods when data is available. The Allegheny
County student population averaged 43,636 students across the nine
school districts, comprising 122 schools (57 elementary, 20 middle, and
18 high schools, and 24 charter/independent schools). County-level data
for 2010-2011 season were not available for 3 school districts.
Figure 2. Four model predictions of confirmed influenza in
Allegheny County using leave one season out validations for the 2010 to
2014 influenza seasons. Model predictions of four negative binomial
models (calendar week, average weekly temperature, average weekly
relative humidity (red), one-week lagged county-level all-cause
absences, temperature, and week model (yellow), one-week lagged
county-level all-cause absences, relative humidity, and week model
(blue), and one-week lagged county-level all-cause absences,
temperature, relative humidity, and week model (purple)) using
leave-one-season-out validation approaches showing model predictions
compared to observed virologically-confirmed influenza cases (black
line) in Allegheny County, Pennsylvania, USA, A) weekly counts during
each of the 2010-2011 to 2014-2015 influenza seasons, B) the change in
predicted cases using modeling including absences compared to a seasonal
model excluding absences (red), and C) the cumulative proportions of
predicted and observed influenza cases for each season.
R2 was obtained using a linear regression, where the
observed cases from the left-out season are the dependent variable and
the independent variable were predicted cases from a negative binomial
model of week-lagged county-level all-cause absences, relative humidity,
temperature, and calendar week.
Figure 3. Mean and relative absolute errors for predictions
using grade-specific absence models to predict influenza in Allegheny
County Pennsylvania from 2010 to 2014 influenza seasons. Mean absolute
errors were estimated from univariate grade-specific weekly absences
models (A), and the relative mean absolute error compared models of
grade-specific weekly absences, week of the year, average weekly
relative humidity, average weekly temperature to models of calendar
week, average weekly relative humidity, and average weekly temperature
(B). Colors reflect the three different school types: red is elementary
school, green is middle school, and blue is high school. Solid black
line refers to a relMAE of 1, where mean absolute errors of the
grade-specific absence models and models excluding absences are the
same.