Table 2.

Summary of articles reviewed.

Reference (first author, year)	Target disease	Place	Period	Input source
Gesteland, 2003 [26]	Bioterrorism	2002, Olympics	2002	Chief complaints from emergency departments
Yan, 2013 [27]	Infectious diseases	Rural China	2012	Symptoms of patients from health facilities, medication sales from pharmacies, and primary school absenteeism
Maciejewski, 2009 [28]	Detection of public health emergencies	Indiana State Department of Health	2009-2010	Symptoms in emergency departments
Thapen, 2016 [29]	Generalized disease nowcasting	United Kingdom	2014	Twitter and GP In Hours weekly bulletin
Thapen, 2016 [30]	Infectious diseases, eg, hay fever and flu	England and Wales	2014	Twitter
Gomide, 2011 [31]	Dengue	Observatório da Dengue website (www.observatorio.inweb.org.br/dengue/)	N/Aa	Twitter
Qi, 2013 [32]	Influenza infection	University campus	Spring 2011	Movement trajectory
Mathes, 2017 [33]	Infectious diseases	New York City	Since 2001	Emergency department visits with infectious diseases such as cough, sore throat, and fever for influenzalike illness
Yih, 2010 [34]	Acute illness for bioterrorism event	Greater Boston area, Greater Twin Cities area, Austin and Travis County, San Mateo County	2007-2008	Ambulatory care encounters
Kleinman, 2005 [16]	Lower respiratory tract infection	Boston area	N/A	Ambulatory care encounters
Dafni, 2004 [35]	Emergency department data	Athens, 2004 Olympic Games	2002-2003	Symptoms in emergency department
Wagner, 2004 [36]	Infectious disease	Utah, Atlantic City	1999	Chief-complaint data
Weng, 2015 [37]	Enterovirus and influenza	Taipei	2010/2011	School-based syndromes
Maciejewski, 2010 [38]	Respiratory illness	State of Indiana	2007	Infectious disease
Higgs, 2007 [39]	Comprehensive tuberculosis data	San Francisco homeless	1991-2002	Tuberculosis
Ali, 2016 [24]	Infectious disease	Pakistan	2011-2015	Chief complaints from emergency departments
Groeneveld, 2017 [25]	Infectious disease	Netherlands	2014/2015	Respiratory tract infection, hepatitis, and encephalitis/meningitis
Kajita, 2017 [22]	Emergency department data	Los Angeles County Department of Public Health, 2015 Special Olympic Games	2015	Monitor health impact
Choi, 2010 [40]	Infectious disease	Hong Kong	2005	Febrile patients
Heffernan, 2004 [41]	Emergency department chief complaint	New York City Department of Health and Mental Hygiene	2001-2002	Infectious disease, eg, respiratory, fever, diarrhea, and vomiting
Takahashi, 2008 [42]	Infectious disease	Massachusetts	2005	Daily syndromic surveillance data
Besculides, 2005 [43]	Infectious disease	New York City	2001-2002	School absenteeism data
Blake, 2016 [44]	Poliomyelitis outbreaks	N/A	2003-2012	Reporting of acute flaccid paralysis cases and laboratory confirmation
Greene, 2012 [45]	Gastrointestinal disease outbreak detection	Kaiser Permanente Northern California	2009	Data streams from electronic medical records
Vilain, 2016 [46]	Infectious disease	French Institute for Public Health Surveillance, Reunion Island	2013-2014	Emergency department visits
Sharip, 2006 [21]	Infectious disease	Los Angeles County	2003-2004	Emergency department syndromic data
Duangchaemkarn, 2017 [47]	Infectious disease	N/A	2016-2017	Chief complaint symptoms

^aN/A: not available.