## Prithwi.github.io

Forecasting a Moving Target: Ensemble Models for ILI Case Count Predictions
Pejman Khadivi∗†
Jiangzhuo Chen‡
Patrick Butler∗†
Elaine O. Nsoesie‡§¶
Sumiko R. Mekaru§
John S. Brownstein§¶
Madhav V. Marathe∗‡
Naren Ramakrishnan∗†
ever, traditional surveillance reports are published with
Modern epidemiological forecasts of common illnesses,
a considerable delay and thus recent research has fo-
such as the flu, rely on both traditional surveillance
cused on mining social signals from search engine query
sources as well as digital surveillance data. However,
volume and social media chatter
most published studies have been retrospective. Con-
One of the pioneering work in this field, was due to
currently, the reports about flu activity generally lags
Ginsberg et al. where ILI case counts are predicted
by several weeks and even when published are revised
from the volume of search engine queries. This work
for several weeks more. We posit that effectively han-
inspired significant follow-on work, such as where
dling this uncertainty is one of the key challenges for
used search query data from Baidu (a
a real-time prediction system in this sphere.

popular search engine in China) to detect influenza
paper, we present a detailed prospective analysis on the
More real-time ILI detection systems
generation of robust quantitative predictions about tem-
have been proposed by modeling Twitter streams.

poral trends of flu activity, using several surrogate data
Apart from such social media sources, there has also
sources for 15 Latin American countries. We present our
been considerable research on exploiting physical indi-
findings about the limitations and possible advantages
cators such as climate data. These primary advantage
of correcting the uncertainty associated with official flu
of such data sources is that the effects are much more
We also compare the prediction accuracy
causal and less noisy. Shaman et. al. explored
between model-level fusion of different surrogate data
this area in detail and found absolute humidity to be a
sources against data-level fusion. Finally, we present
good indicator of influenza outbreaks.

a novel matrix factorization approach using neighbor-
While the aforementioned works have made impor-
hood embedding to predict flu case counts. Comparing
tant strides, there are important areas that have been
our proposed ensemble method against several baseline
relatively less studied. First, only a few works have fo-
methods helps us demarcate the importance of different
cused on combining multiple data sources to aid
data sources for the countries under consideration.

in forecasting. In particular, to the best of our knowl-edge there has been no work that investigates the com-
bination of social indicators and physical indicators toforecast ILI incidence. Second, and more importantly,
Surveillance reports published by health organizations
official estimates as reported by health organizations
are one of the primary resources for monitoring in-
(e.g., WHO, PAHO) are often lagged by several weeks
fluenza like illness (ILI) cases. For years, these reports
and even when reported are typically revised for several
have been the primary source of information used by
weeks before the case counts are finalized. Real-time
healthcare officials for policy making decisions. How-
prediction systems must be designed to handle the fore-casting of such a ‘moving target'. Finally, most existing
∗Dept. of Computer Science, Virginia Tech, Blacksburg, VA,
works have been retrospective and not set in the context
of a formal data mining validation framework. To over-
†Discovery Analytics Center Vir-
come these deficiencies, we propose a novel approach to
ginia Tech, Blacksburg, VA, USA
‡Network Dynamics and Simulation Science Laboratory, Vir-
ILI case count forecasting. Our contributions are:
ginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA,
• Our approach integrates both social indicators and
physical indicators and thus leverages the selec-
§Childrens Hospital Informatics Program, Boston Childrens
tive superiorities of both types of feature sets.

Hospital, Boston, MA, USA
¶Department of Pediatrics, Harvard Medical School, Boston,
We systematize such integration using a novel ma-
trix factorization-based regression approach using
these works, we curated a custom ILI related keyword
dictionary which is described in details in Section
Physical indicators for detecting ILI inci-
dence levels: Tamerius et al. investigated the exis-
tence of seasonal cycles of influenza epidemics in differ-
ent climate regions. For the said work, they considered
climatic information from 78 globally distributed sites.

Using logistic regression they found that, strong corre-lations exist between influenza epidemics and weather
conditions, especially when conditions are cold-dry or
humid-rainy. Similarly, exciting results were reported
by Shaman et. al. in where they discovered ab-
solute humidity to be a key indicator of flu. To uncoverthese relationships they used non-linear regressors such
as Kalman filters, and this was a key inspiration for usin finding a uniform model for the varied data sourcesas explained in Section
Our ILI data pipeline, depicting six different data sources
Event dynamics modeling: Denecke et al.
used in this paper to forecast ILI case counts.

proposed an event-based approach for early predictionof ILI threats
Their method (M-Eco) considers
neighborhood embedding, thus helping account for
multiple resources such as Twitter, TV reports, online
non-linear relationships between the surrogates and
news articles, and blogs and uses clustering to identify
the official ILI estimates.

signals for event detection. Network dynamic solutions
• We investigate the efficacy of combining diverse
have also been used to study the behavior of an
sources using data fusion and model fusion meth-
epidemic in a society.

ods. We also discuss their relative strengths.

Problem Formulation
• We propose different ways of handling uncertainties
In this section, we formally introduce the problem. LetP
in the official estimates and factor these uncertain-
= hP1, P2, . . , PT i denote the known total weekly ILI
ties into our prediction models.

case count for the country under consideration, wherePt denotes the case count for time point t and T denotes
• Finally, we present a detailed and prospective
the time point till which the ILI case count is known.

analysis of our proposed methods by comparing
Corresponding to the ILI case count data, let us denote
predictions from a near-horizon real time prediction
the available surrogate information for the same country
system to official estimates of ILI case counts in 15
by X = hX1, X2, . . , XT 1i, where T 1 is the time point
countries of Latin America.

till which the surrogate information is available and Xtdenotes the surrogate attributes for time point t (> T ).

The problem we desire to solve is to find a predictive
Related work naturally falls into the categories of social
model (f ) for the case count data, as presented formally
media analytics, physical indicators, and event dynam-
ics modeling. These are next described as follows:
Social media analytics: Most relevant works us-
In this paper, in order to better understand the
ing social media analytics focuses on Twitter, specifi-
importance of different sources, we assume that the ILI
cally, by tracking a dictionary of ILI-related keywords
activities in different countries are independent of each
in the data stream. Such investigations have often fo-
cused on the importance of diversity in keyword lists,
Methods Focusing on the methods, we employ
e.g., In Kanhabua and Nejdl used clustering
non-linear temporal regressions over the surrogate at-
methods to determine important topics in Twitter data,
tributes to forecast the case count using three mod-
constructed time series for matched keywords, and used
els: (a) Matrix Factorization Based Regression (MF),
Jaccards coefficient to characterize the temporal diver-
(b) Nearest Neighbor Based Regression (NN), and (c)
sity of tweets. They noted, that such temporal diversity
Matrix Factorization Regression using Nearest Neighbor
may be correlated with real-world ILI outbreaks. In
embedding (MFN). For each of the methods, we define
the authors studied the dynamics between the change
two parameters: β and α. α is the lookahead window
in circulated tweets and the H1N1 virus. Inspired by
length, denoting distance of the time point for predic-
tion from T ; β is the lookback window length denoting
that we only compute the error between the predicted
the number of time points to look back in order to find
label values and the actual label values i.e., the nth
the regression relation between the case count and the
column of the prediction matrix M.

surrogate data.

behind this choice is the fact that unlike traditional
We define regression vectors Vt and labels Lt, ∀t =
recommender systems we are only concerned with the
1, . . , T as below:.

label column and can sacrifice reconstruction accuracies
hPt−β−α, Xt−β−α, Pt+1−β−α, Xt+1−β−α, . . ,
for other columns.

Pt−α, Xt−αi
The lookback window β, the factor size f and the
regularization parameter λ1 are estimated using cross-validation and the final prediction for time point T 0 is
The regression vector for predicting the case count at
time point T 0(T + α > T 0 > T ) is given by equation
hPT 0−β−α, XT 0−β−α, Pt+1−β−α, Xt+1−β−α, . . ,P
T 0−α, XT 0−αi
(NN): For our second class of models, viz.

Under these definitions we describe the models as fol-
Vt represents the re-
Matrix Factorization Based Regression
gression attributes and Lt denote the correspond-
(MF): Matrix Factorization is a well accepted tech-
Also, let us define the set N (i)
Vk is one of the top K nearest neighbors of Vi}
predict user preferences from incomplete user rat-
where K indicates the maximum number of nearest
ings/information. Typically a user-preference ma-
neighbors considered. The predicted count b
trix is factored into an user-factor and factor-preference
time point T 0 is given as:
matrix. However, such factorizations are in-cognizant
of any temporal continuity. As such to enforce tempo-
ral continuity, to predict for the time point T 0(T + α >
T 0 > T ) we use the regression vectors and labels as de-
Here θk indicates the weight assigned to the kth nearest
fined earlier, to define a m × n prediction matrix M, as
neighbor. Typically the inverse Euclidean distances to
given in equation
VT 0 are chosen as the weights.

3.1.3
Matrix Factorization Based Regression
using Nearest Neighbor Embedding (MFN): It
has been shown in that matrix factorization us-
ing nearest neighbor constraints can outperform classi-
cal matrix factorization approach as well as traditionalnearest neighbor approaches towards recommender sys-
The prediction matrix is factorized into a f × m
tems. Drawing inspirations from the result, we modify
factor-feature matrix U and a f × n factor-prediction
the method to suit the temporal nature of our problem
in similar ways as described in section We again
define a similar prediction matrix M (see equation
Following we define the matrix decomposition rule
i,j is the baseline estimate given by:
M represents the all-element average and b
represents the column wise deviations from the average
The key difference between equation and the one
and is generally a free-parameter, i.e., it is fitted as
is that we don't have any term for
part of the optimization problem. U and F matrix are
implicit feedback and, further, only the top K neighbors
estimated by minimizing the error function:
as found through Euclidean distance are used.

∗, F, U = argmin(
model is fitted using Eqn as given below:
b∗, F, U, x∗ = argmin(
1 is a regularization parameter. An important
design criteria in the error function of Eqn is the fact
Ensemble Approaches
so that the final prediction for the T th data point is
In the last section, we described different strategies to
correlate a specific source with the ILI case count of
a specific country and predict future ILI counts.

The fitting function is given by equation
practice, we desire to work with a multitude of data
sources and there are two broad ways to accomplish this
objective: (a) data level fusion, where a single regressor
C b∗, C F, C U, C x∗ = argmin(
is constructed from different data sources to the ILI case
count, and (b) model level fusion, where we build one
regressor for each data source and subsequently combine
the predictions from the models. In this section, wedescribe these fusion methods.

Experimental results
As before the free parameters are estimated through
with both methods are presented in Section
Data level fusion: Here we express the feature
Forecasting a Moving Target
vector X , as a tuple over all the different data sources
One of the key challenges in creating a prospective
and then proceed with any one of the regression meth-
ILI case count predictor is the fact that the official
ods as outlined in Section For example, while com-
estimates are often delayed and, furthermore, even when
bining Twitter and weather data sources (see Fig.
published the estimates are revised over a number of
the feature vector X is given by:
weeks before these become finally stable.

paper, we concentrate on 15 Latin American countries
as described in Section and consider the official ILI
where Tt and Wt denote attributes derived from Twitter
estimates from the Pan American Health Organization
and weather, respectively.

(PAHO).Thus we can categorize PAHO count values
Model level fusion: In this approach, the mod-
downloaded on any week into three different types: (a)
els are combined using matrix factorization regression
the unknown PAHO counts represented by ¨
with nearest neighbor embedding by comparing the pre-
known and stable PAHO counts denoted by ˙
diction estimates from each model with the actual esti-
the known and unstable PAHO counts denoted by ˜
mate (since the ground truth can change as well) and the
While we desire to predict ¨
Pt, the uncertainty associated
average ILI case count for the month for the particular
Pt introduces errors in the predictions. In this
country (to help organize a baseline). Let us denote the
section, we study the effects of such unstable data and
average ILI case count for a particular calendar month
propose three different models to adjust these unstable
I for a given country by:
values to more accurate ones.

Figure plots the relative error of an unstable
PAHO data series w.r.t. its final estimate, as a function
of time. It can be seen that different countries have
Considering C different sources and hence C different
different stability characteristics: for some countries,
models, let us denote the prediction for the tth time
PAHO count values are stabilized very slowly whereas
point from the cth model by
for others they stabilize faster (esp as the number of
Using these definitions we can now proceed to
updates for a week increases).

Stability behavior of
describe the fusion model.

Essentially, the model is
PAHO count values were also found to be dependent on
similar to the one described in Section where
the time of the year as shown in Fig. To plot this
the differences can be found in the way we construct
curve for Argentina, we categorized any week with less
the feature vectors. Similar to Eqn we construct a
than 100 cases to belong to a low season, greater than
prediction m0 × n0 matrix for fusion given by
300 to be a high season, and the remaining values to be
the tth row is represented by equation
mid season (the thresholds were different for differentcountries).

At the same time, the PAHO official updates pro-
vide an indication of the number of samples used to gen-
Then similar to Eqn we factor this matrix into
erate the case count estimate. Preliminary experiments
latent factors, C U , C F , C b∗ as given by Eqn
show that this size is correlated with the accuracy of ILI
case counts. In other words, in general, larger values of
statistical population size results in smaller relative er-
rors for ILI case count. Thus using both the number
C Mi,k − µi + C bk )C xk
values before and after correction for each countryare shown in Figure
While in a few cases, we
do not experience any improvement, in countries suchas Argentina and Paraguay, we experience significantimprovements.

Average relative error of PAHO count values with respect
to stable values. (a) Comparison between Argentina and Colombia(b) Comparison between different seasons for Argentina.

of samples and the lag in uploading the week data, wecan use machine learning techniques to revise the offi-cially published PAHO estimates. Preliminary resultsshow that for different seasons and different countries,we encounter different stability patterns. Therefore, anyPAHO count adjustment method should be customized
Figure 3: Average relative error of PAHO count values before and
for seasons and countries separately.

after correction for different countries.

Let us assume that ˙
P is the set of stable PAHO
counts for a specific country.

Also, assume that the
Finally, similar to Eqn in addition to P
sequence of updates for each stable PAHO count value
can use only time difference (m) or size of population
is available. In other words, for ˙
Pi we have the following
) to correct unstable PAHO values.

these corrections on overall accuracy of predictions are
Pi = P (1), P (2), ., P (m), .

explored in Section
Experimental Setup
is the value of P
i after m weeks of update.

After recognizing high, low, and mid-season months
Reference Data. In this paper, we focus on
for the country, we can categorize each ˙
15 Latin American countries viz.

to one of these categories.

Then, for category S, an
livia, Costa Rica, Colombia, Chile, Ecuador, El Sal-
adjustment dataset is constructed named as P S
vador, Guatemala, French Guiana, Honduras, Mexico,
is defined as follows:
Nicaragua, Paraguay, Panama and Peru. We collectedweekly ILI counts from the official Pan American Health
), ., (m, P (m), ˙
Organization (PAHO) w
every day from January 2013
Each member of P S
is a tuple with four entries:
to August 2013. The estimates downloaded every day
the first entry denotes the time slot that the sample
for each country contain data from January 2010 to
belongs to; the second entry is the actual unstable value
the latest available week on the day of collection. This
of Pi; the third entry is the related stable value; and
dataset is stored in a database we refer to as the Tem-
is the size of the statistical population for
poral Data Repository (TDR). The TDR is also times-
tamped so that for any given day, we can readily re-
In the next step, a linear regression algorithm is
trieve the ILI case counts that were download on that
used to adjust unstable PAHO values. In order to adjust
day. This is important as historic data may be updated
the PAHO values in the mth time slot of season S, we
by PAHO even a number of weeks after the first up-
date. For the purpose of experimental validation we
set to learn a0, a1, a2, and a3 coefficients in
the following equation:
used the data for the period Jan 2010 to December 2012as the static training set. We considered Wednesdays of
the weeks as a reference day within a week. For each
Wednesday from Jan 2013 to July 2013, we used the lat-
is the adjusted PAHO count value for the
est available PAHO data in TDR for that day and pre-
mth time slot.

dicted 2 weeks from the last available week for which the
Experimental results show that this adjustment
PAHO data was available. These predictions are next
method results in more accurate known PAHO values.

evaluated against the final ILI case count as downloaded
Average relative errors of the published unstable PAHO
on September 1, 2013 and we report the performance ofour algorithms in Section
Evaluation criteria. We evaluate the prediction
shifted to capture the words commonly searched during
accuracy of the different algorithms using a modified
the tail of the infection. This entire exercise provided us
version of percentage relative error:
some interesting terms like ginger which has been used
as a natural herbal remedy in the eastern world. We
also found popular flu medications such as Acemuk and
Oseltamivir, which are also sold under the trade name
of Tamiflu as highly correlated search queries, especially
s and te indicate the starting and the ending
time point for which predictions were generated. N
particularly for Argentina.

indicates the number of time points over the same time
Final filtering. The set of terms obtained from
query expansion and correlation analysis were then
p = te − ts + 1). Note that the measure
is scaled to have values in [0, 4] and the denominator is
pruned by hand to obtain a vocabulary of 151 words.

designed to not over-penalize small deviations from the
We then performed a final correlation check and re-
true ILI case count (e.g., when the true case count is
tained a final set of 114 words.

0 and the predicted count is 1). It is to be noted that
Google Flu Trends (F ): Google Flu Trends
the accuracy metric so defined is non-convex and is in
based on and provided by Google.org which gives
Surrogate data sources. Before describing our
weekly and up-to-date ILI case count estimates using
data sources in detail, we describe our overall method-
search query volumes. Of the countries under consid-
ology for organizing a flu-related dictionary (for track-
eration, GFT provides weekly estimates for only 6 of
ing in multiple media such as news, tweets, and search
them viz. Argentina, Bolivia, Chile, Mexico, Peru and
Paraguay. These estimates are typically at a different
Dictionary creation. The keywords relating
scale than the ILI case counts provided by PAHO and
to ILI were organized from a seed set of words and
therefore need to be scaled accordingly. We collected
expanded using a combination of time-series correlation
this data weekly on Monday from Jan 2013 to Aug 2013.

analysis and pseudo-query expansion.

(The data downloaded on a particular day contains the
of keywords (e.g., gripe) was constructed in Spanish,
entire time-series from 2004 to the corresponding week.)
Portuguese, and English using feedback from our in-
Google Search Trends (S): Google Search
house subject matter experts.

Trends (GST, is an-
Pseudo-query expansion. Using the seed set,
other tool provided by Google. Using this tool we can
we crawled the top 20 web sites (according to Google
download an estimate of search query volume as a per-
Search) associated with each word in this set.

centage over its own temporal history, filtered geograph-
also crawled some expert sites such as the official
ically. We download the search query volume time series
CDC website and equivalent websites of the coun-
for the 114 keywords described earlier and convert the
tries under consideration, detailing the causes, symp-
percentage measures to absolute values using a static
toms and treatment for influenza.

dataset we downloaded on Oct 2012 when Google Search
crawled a few hand-picked websites such as
Trends used to provide absolute query volumes.

Twitter (T ): Twitter data was collected from
We filtered the words from
Datasift.com and geotagged using an in-house geocoder.

these sites using standard language processing filtering
We lemmatized the tweet contents and used language
techniques such as stopword removal and Porter stem-
detection and POS tagging to help differentiate relevant
ming. The filtered set of keywords were then ranked
from irrelevant uses of our keywords (e.g., the Spanish
according to the absolute frequency of occurrence. The
word gripe, meaning flu, is part of our flu keyword
top 500 words for Spanish and English were then se-
list as opposed to the undesired and unrelated English
For example, words such as enfermedad and
word ‘gripe'). The resulting analysis yields a weekly
pandemia were obtained from this step.

occurrence count of our dictionary in tweets.

Time-series correlation analysis. Next we used
HealthMap (H): Similar to Twitter, we also
Google Correlate (now a part of Google Trends) to iden-
collect flu-related news stories using HealthMap
tify keywords most correlated with the ILI case count
an online global disease alert sys-
time-series for each country. Once again these words
tem capturing outbreak data from over 50,000 electronic
were found to be a mix of both English and Spanish. As
sources. Using this service we receive flu-related news
an added step in this process, we also compared time-
as a daily feed which is similarly enriched and filtered to
shifted ILI counts: left-shifted to capture the words
obtain a multivariate time series over lemmatized ver-
searched leading up to the actual flu infection and right-
sion of the keywords. While Twitter is more suitable to
ILI case count prediction accuracy for Mexico using
OpenTable data as a single source, and by combining it with all other
ascertain general public response, the HealthMap data
sources using model level fusion on uncorrected ILI case count data.

provides more detailed information but may capture the
trends at a slower rate. Thus each of these sources offers
utility in capturing different surrogate signals: Twitter
offers leading but noisy indicators whereas HealthMap
provides a slightly delayed but more reliable indicator.

OpenTable (O): We also use data on trends of
stable estimates of ILI case counts are considered to be
restaurant table reservations, initially studied in to
the estimates downloaded from PAHO on Oct 1, 2013.

be a potential early indicator for outbreak surveillance,
All models considered here were used to forecast 2 weeks
as another surrogate for ILI detection. This novel data
beyond the latest available PAHO ILI estimates. Key
stream is based on the postulate that a higher than
findings are presented in Table. We analyze some
average number of restaurants with table availability in
important observations from this table next.

a region can serve as an indicator of an event of interest,such as increase in flu cases.

Table availability was
monitored using OpenTable an online restaurant reservation site with 28,000restaurants at the time of this writing. Daily searcheswere performed starting from September 2012 for atable for two persons at lunch and dinner; between12:30-3pm, and between 6-10:30pm. Data was collectedfor Mexico by city (Cancun, Mexico City, Puebla,Monterrey, and Guadalajara) and for the entire country.

The daily proportion (proportion used due to changes inthe number of restaurants in the system) of restaurants
Figure 4: Accuracy of different methods for each country.

with available tables was aggregated as a weekly time-
Can we ‘beat' Google Flu Trends with our
custom dictionary?
The key difference between
Weather (W): All of the previously described
Google Flu Trends (which can be considered as a base
data sources can be termed as non-physical indicators
rate) and Google Search Trends is that the former uses a
which can work suitably as indirect indicators about the
closed dictionary whereas we constructed the dictionary
state of the population with respect to flu by exposing
to use with GST. As can be seen Table for majority
different population characteristics. On the other hand,
of the common countries (countries for which data from
meteorological data can be considered a more direct
both GST and GFT is present), regressors running on
and physical driver of influenza transmission It
GST consistently outperform those running on GFT
has been shown in that absolute humidity
(with Mexico and Peru being the exception). Thus we
can be directly used to predict the onset of influenza
posit that the GST model devised here is a sufficiently
epidemics. Here, we collect several other meteorological
close approximation to GFT, with the added advantages
indicators such as temperature and rainfall in addition
of having access to raw level data and being available
to humidity from the Global Data Assimilation System
for more countries than GFT (only 6 of the 15 countries
(GDAS). We accessed this data in GRIB format from
we consider are present in the GFT database).

at a resolution of
Which is the optimal regression model? From Ta-
1o lat/long interval.

However, looking at all the
ble we can also analyze the three different regressors
lat/long for a country can often lead to noisy data.

proposed in Section with respect to overall accuracy.

As such we filtered the downloaded data and used the
With respect to each individual source, we can see that
indicators only around the surveillance centers. Finally,
matrix factorization with nearest neighbor embedding
we generated a times-series by using weekly-averages
(MFN) performs the best in average over the countries.

of this date, for each country. We collected this data
For some countries such as Panama, when using only
weekly from Jan 2013 to August 2013.

GST, MFN performs poorer than vanilla MF; neverthe-
less the average accuracy over all countries for any given
In this section, we present an exhaustive set of experi-
data source is best when using MFN.

ments evaluating our algorithms over 6 months of pre-
Which is the best strategy to combine multiple
dictions from Jan 2013 to August 2013. The final and
As shown in Table in overall,
model level fusion works better than data level fusion.

Comparing forecasting accuracy of models using individual sources. Scores in this and other tables are normalized to [0,4] so that
4 is the most accurate.

Table 2: Comparison of prediction accuracy while combining all data sources and using MFN regression.

Comparison of prediction accuracy while using model level fusion on MFN regressors and employing PAHO stabilization.

Discovering importance of sources in Model level fusion on MFN regressors by ablating one source at a time.

For 8 of the 15 countries, model level fusion works
wherein we remove one data source at a time from our
appreciably better than data level fusion, while the
model level MFN fusion framework and contrast accu-
reverse trend is seen for 4 other countries.

racies. While removing the weather data degrades the
showcases the importance of considering both kinds of
accuracy score the most, removing the social indicators
fusion depending on the country of interest.

also degrades the score to varying degrees. Thus we
How effective are we at forecasting a moving
posit that it is important to consider both the physical
PAHO target? As shown in Table our corrected
and social indicators to get a refined signal about the
estimates using both the number of samples and the
prevalent ILI incidence in the population.

weeks ahead from the upload date are generally better.

How relevant is restaurant reservation data to
It is instructive to note that our correction strategy
forecasting ILI? All the results thus far do not con-
is able to increase the overall accuracy only by a
sider the OpenTable reservation data, since this source
score of approximately 0.05 over all the countries, for
is available only for Mexico (among the countries stud-
some countries such as Mexico and Argentina (for
ied here). We considered table availability for different
which the data update is typically noisy) we obtain a
time ranges and compared performance using our MFN
substantial improvement of scores. This suggests that
model. As Table demonstrates, we obtain the best
the correction strategy may be selectively applied when
performance when considering both lunch and dinner
forecasting for certain countries.

reservation data. Nevertheless, we have observed that
How do physical vs social indicators fare against
including this source as part of the ensemble decreases
each other? From Table we see that the data source
the overall accuracy by 0.01 over the uncorrected ILI
with the best single accuracy happens to be the physical
case count data. Thus it is our opinion that although
indicator source, i.e., weather data. However, Table
the reservation data could exhibit some signals about
conveys a mixed story. Here we conduct an ablation test,
prevalent ILI conditions, it is also a surrogate for non-
health conditions (e.g., social unrest), which must be
[4] K. Lee, A. Agrawal, and A. Choudhary, "Real-time
factored out to make the data source more useful.

disease surveillance using twitter data: demonstration
Finally, we present Figure where we compare
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for each country the accuracies of prediction from the
2013, pp. 1474–1477.

best individual source, with those from both data level
[5] N. Kanhabua and W. Nejdl, "Understanding the diver-
sity of tweets in the time of outbreaks," in Proceedings
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Source: https://prithwi.github.io/resources/papers/prithwi_sdm14_MFN.pdf

The Fair Labor Standards Act Exemptions and the Pharmaceuticals Industry: Are Sales Representatives Entitled to Overtime?Steven I. Locke Follow this and additional works at: Part of the nd the Recommended CitationSteven I. Locke (2009) "The Fair Labor Standards Act Exemptions and the Pharmaceuticals Industry: Are Sales RepresentativesEntitled to Overtime?," Barry Law Review: Vol. 13: Iss. 1, Article 1.Available at:

ADVANCES IN NEUROPSYCHIATRY Neuropsychiatry of the basal ganglia J Neurol Neurosurg Psychiatry 2002;72:12–21 This review aims to relate recent findings describing the parts of the basal ganglia closest to limbic role and neural connectivity of the basal ganglia to the structures and that are involved in cognitive and clinical neuropsychiatry of basal ganglia movement