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Volume 26, Number 11—November 2020
Research

Nowcasting (Short-Term Forecasting) of Influenza Epidemics in Local Settings, Sweden, 2008–2019

Armin SprecoComments to Author , Olle Eriksson, Örjan Dahlström, Benjamin John Cowling, Matthew Biggerstaff, Gunnar Ljunggren, Anna Jöud, Emanuel Istefan, and Toomas Timpka
Author affiliations: Linköping University Department of Health, Medicine, and Caring Sciences, Linköping, Sweden (A. Spreco, E. Istefan, T. Timpka); Center for Health Services Development, Region Östergötland, Linköping (A. Spreco, T. Timpka); Linköping University Department of Computer and Information Science, Linköping (O. Eriksson, T. Timpka); Linköping University Department of Behavioral Sciences and Learning, Linköping (Ö. Dahlström); World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, The University of Hong Kong School of Public Health, Hong Kong (B.J. Cowling); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (M. Biggerstaff); Karolinska Institutet Department of Neurobiology, Care Sciences, and Society, Huddinge, Sweden (G. Ljunggren); Public Health Care Services Committee Administration, Region Stockholm, Stockholm, Sweden (G. Ljunggren); Lund University Faculty of Medicine, Department of Laboratory Medicine, Division of Occupational and Environmental Medicine, Lund, Sweden (A. Jöud); Lund University Faculty of Medicine, Clinical Sciences, Division of Orthopedics, Lund (A. Jöud); Scania University Hospital Department for Research and Development, Lund (A. Jöud)

Main Article

Table 2

Performance of peak-timing and peak-intensity predictions from evaluation of nowcasting for detection and prediction of local influenza epidemics, Sweden, 2008–2019

Influenza virus activity Time-to-peak*
Peak-intensity category, cases/day/100,000 population†§
Prediction date Predicted Error Interpretation Predicted Factual Interpretation
2009 A(H1N1)
Stockholm 2009 Sep 13 8 56 Poor Medium (5.0) Very high (12.4) Poor
West Gothia 2009 Sep 13 8 56 Poor Low (2.2) Very high (13.7) Poor
Scania
2009 Sep 25
10
42
Poor

Low (1.4)
High (6.4)
Poor
2010–11 A(H1N1) and B
Stockholm 2011 Jan 14 10 28 Poor Medium (3.4) Medium (3.5) Excellent
West Gothia 2011 Jan 14 10 14 Poor Medium (4.3) High (6.1) Tolerable
Scania
2011 Jan 10
11
22
Poor

Medium (2.9)
High (5.5)
Poor
2011–12 A(H3N2)
Stockholm 2012 Feb 27 8 −8 Tolerable High (7.4) Very high (9.4) Good
West Gothia 2012 Feb 27 8 −8 Tolerable High (7.8) Very high (9.6) Good
Scania
2012 Feb 27
8
−8
Tolerable

Medium (4.0)
High (6.8)
Poor
2012–13 A(H3N2), A(H1N1), and B
Stockholm 2013 Feb 10 8 −7 Good Very high (10.3) Very high (12.2) Excellent
West Gothia 2013 Feb 10 8 −7 Good Very high (10.3) Very high (11.9) Excellent
Scania
2019 Feb 8
10
−7
Good

High (7.3)
Very high (10.7)
Good
2013–14 A(H3N2), A(H1N1), and B
Stockholm 2014 Feb 16 8 −7 Good Medium (2.7) Medium (3.0) Excellent
West Gothia 2014 Feb 16 8 −7 Good Medium (3.5) Medium (2.9) Excellent
Scania
2014 Feb 17
8
−1
Excellent

Medium (3.2)
Medium (4.2)
Excellent
2014–15 A(H3N2) and B
Stockholm 2015 Feb 22 8 6 Good Medium (4.5) High (6.5) Tolerable
West Gothia 2015 Feb 22 8 6 Good Very high (7.9) Very high (8.3) Excellent
Scania
2015 Feb 14
9
0
Excellent

Medium (3.9)
Very high (8.1)
Poor
2015–16 A(H1N1) and B
Stockholm 2016 Feb 7 8 0 Excellent High (6.7) Very high (8.2) Tolerable
West Gothia 2016 Feb 7 8 7 Good High (7.6) Very high (11.6) Good
Scania
2016 Feb 6
9
7
Good

Medium (4.3)
Very high (10.4)
Poor
2016–17 A(H3N2)
Stockholm 2017 Jan 1 8 −7 Good Very high (8.2) High (6.8) Good
West Gothia 2017 Feb 12 8 7 Good Medium (3.3) Medium (3.7) Excellent
Scania
2017 Feb 5
8
14
Poor

Medium (4.2)
Medium (5.1)
Excellent
2017–18 A(H3N2) and B
Stockholm 2018 Feb 18 8 −7 Good Very high (14.4) Very high (11.6) Excellent
West Gothia 2018 Feb 18 8 0 Excellent Medium (5.2) High (5.9) Good
Scania
2018 Feb 4
8
14
Poor

Medium (4.2)
Very high (14.0)
Poor
2018–19 A(H1N1)
Stockholm 2019 Feb 3 8 0 Excellent Very high (14.4) High (6.2) Poor
West Gothia 2019 Feb 3 8 7 Good Medium (4.0) Medium (3.4) Excellent
Scania 2019 Feb 3 8 −7 Good Medium (2.8) Medium (5.2) Excellent

*Time-to-peak (days) determined using syndromic telenursing data. Positive value means that the peak was predicted to be reached before the actual peak occurs, whereas negative value means that the peak is predicted after the actual peak occurs.
†Peak-intensity category determined using clinical influenza-diagnosis data.
§Using clinical influenza data (Table 1), the start of the epidemic was detected on December 27. On February 1, using syndromic data, the peak in clinical influenza data was forecasted to occur 8 days later (February 9), but the peak actually occurred on February 2 (7 days earlier than forecasted). Also, on February 1, the clinical influenza data intensity was forecasted to be high.

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