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Detecting the start of an influenza outbreak using exponentially weighted moving average charts.

Steiner SH, Grant K, Coory M, Kelly HA - BMC Med Inform Decis Mak (2010)

Bottom Line: Influenza viruses cause seasonal outbreaks in temperate climates, usually during winter and early spring, and are endemic in tropical climates.The chart is shown to provide timely signals in an example application with seven years of data from Victoria, Australia.The EWMA control chart could be applied in other applications to quickly detect influenza outbreaks.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept. of Statistics, University of Waterloo, Ontario, Canada. shsteine@math.uwaterloo.ca

ABSTRACT

Background: Influenza viruses cause seasonal outbreaks in temperate climates, usually during winter and early spring, and are endemic in tropical climates. The severity and length of influenza outbreaks vary from year to year. Quick and reliable detection of the start of an outbreak is needed to promote public health measures.

Methods: We propose the use of an exponentially weighted moving average (EWMA) control chart of laboratory confirmed influenza counts to detect the start and end of influenza outbreaks.

Results: The chart is shown to provide timely signals in an example application with seven years of data from Victoria, Australia.

Conclusions: The EWMA control chart could be applied in other applications to quickly detect influenza outbreaks.

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Related in: MedlinePlus

EWMA with λ = 0.5 Applied to Victoria Laboratory Notification Data.
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Figure 2: EWMA with λ = 0.5 Applied to Victoria Laboratory Notification Data.

Mentions: To apply the EWMA chart we need to choose the smoothing constant, λ, and threshold, h. Due to the usually rapid increase and decrease in the number of laboratory notifications of influenza we would want only a little smoothing. Thus, we would choose a fairly large value for λ like 0.5. Figure 2 shows the EWMA chart for the Victorian laboratory notification data with λ = 0.5 (both left and right panels show the same chart, the right panel restricts the range of the vertical axis). This value for λ is larger than that used in most industrial applications were the goal is to detect more gradual sustained changes. Note that with λ = 1, the EWMA control chart simplifies to the Shewhart control chart [3] as shown in Figure 1.


Detecting the start of an influenza outbreak using exponentially weighted moving average charts.

Steiner SH, Grant K, Coory M, Kelly HA - BMC Med Inform Decis Mak (2010)

EWMA with λ = 0.5 Applied to Victoria Laboratory Notification Data.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2909986&req=5

Figure 2: EWMA with λ = 0.5 Applied to Victoria Laboratory Notification Data.
Mentions: To apply the EWMA chart we need to choose the smoothing constant, λ, and threshold, h. Due to the usually rapid increase and decrease in the number of laboratory notifications of influenza we would want only a little smoothing. Thus, we would choose a fairly large value for λ like 0.5. Figure 2 shows the EWMA chart for the Victorian laboratory notification data with λ = 0.5 (both left and right panels show the same chart, the right panel restricts the range of the vertical axis). This value for λ is larger than that used in most industrial applications were the goal is to detect more gradual sustained changes. Note that with λ = 1, the EWMA control chart simplifies to the Shewhart control chart [3] as shown in Figure 1.

Bottom Line: Influenza viruses cause seasonal outbreaks in temperate climates, usually during winter and early spring, and are endemic in tropical climates.The chart is shown to provide timely signals in an example application with seven years of data from Victoria, Australia.The EWMA control chart could be applied in other applications to quickly detect influenza outbreaks.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept. of Statistics, University of Waterloo, Ontario, Canada. shsteine@math.uwaterloo.ca

ABSTRACT

Background: Influenza viruses cause seasonal outbreaks in temperate climates, usually during winter and early spring, and are endemic in tropical climates. The severity and length of influenza outbreaks vary from year to year. Quick and reliable detection of the start of an outbreak is needed to promote public health measures.

Methods: We propose the use of an exponentially weighted moving average (EWMA) control chart of laboratory confirmed influenza counts to detect the start and end of influenza outbreaks.

Results: The chart is shown to provide timely signals in an example application with seven years of data from Victoria, Australia.

Conclusions: The EWMA control chart could be applied in other applications to quickly detect influenza outbreaks.

Show MeSH
Related in: MedlinePlus