Tracking of Death Case So Flassa Feverout Breakinnig Eriausinga Modifiedewma Control Chart

LassafeverremainsarecurrentandendemicpublichealththreatinNigeria,withmortalitythatisoftenseasonal,over-dispersed,anddifficulttomonitorusingclassical,threshold-basedsurveillancemethods.ThisstudyappliedaModifiedExponentiallyWeightedMovingAverage(MEWMA)controlchart,developedbyKhanetal.(2017),tomonitorweeklyLassafeverdeathsinNigeriausingsurveillancedataobtainedfromtheNigeriaCentreforDiseaseControl(NCDC)coveringJanuary2021toSeptember2025(244weeks).In-controlprocessparameterswereestimatedfromabaselineperiod,andtheMEWMAstatisticwasconstructedusingthesmoothingparameterλ=0.2,controlchartcoefficientL=2.793,k=λ/2,andanominalin-controlAverageRunLength(ARL₀)of370.Descriptiveanalysisshowedthatweeklydeathswereapproximatelynormallydistributed,withnomarkedskewnessorextremeoutliers,whileatimeplotrevealednaturalfluctuationswithoutanimmediatelyobviouspattern.TheModifiedEWMAchart,however,detectedseveralstatisticallysignificantout-of-controlsignals,mostprominentlyin2024,indicatingperiodswhenLassafeverdeathsroseabovetheexpectedbaseline.Similar,lesspronouncedsignalswereobservedin2021,2022,2023,andearly2025,suggestingarecurringseasonalorperiodicoutbreakpattern.ThesefindingsdemonstratethattheModifiedEWMAchartisasensitiveandpracticalearly-warningtoolforLassafevermortalitysurveillanceinNigeria,anditsadoptionbypublichealthauthoritiescouldsupportmoretimelyoutbreakresponse.

Lassafever; Modified EWM Acontrol chart; Statistical process control; Average Run Length

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