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Estimating influenza deaths in Canada, 1992-2009.

Schanzer DL, Sevenhuysen C, Winchester B, Mersereau T - PLoS ONE (2013)

Bottom Line: To assess their robustness, the annual estimates derived from different parameterizations of the regression model for all-cause mortality were compared.In comparison, we attributed an estimated 740 deaths (95%CI, 350-1500) to A(H1N1)pdm09.Annual estimates from different model parameterizations were strongly correlated, as were estimates for mortality and morbidity; the higher A(H1N1)pdm09 burden in younger age groups was the most notable exception.

View Article: PubMed Central - PubMed

Affiliation: Centre for Communicable Diseases and Infection Control, Infectious Disease Prevention and Control Branch, Public Health Agency of Canada, Ottawa, Ontario, Canada.

ABSTRACT

Background: Poisson regression modelling has been widely used to estimate the disease burden attributable to influenza, though not without concerns that some of the excess burden could be due to other causes. This study aims to provide annual estimates of the mortality and hospitalization burden attributable to both seasonal influenza and the 2009 A/H1N1 pandemic influenza for Canada, and to discuss issues related to the reliability of these estimates.

Methods: Weekly time-series for all-cause mortality and regression models were used to estimate the number of deaths in Canada attributable to influenza from September 1992 to December 2009. To assess their robustness, the annual estimates derived from different parameterizations of the regression model for all-cause mortality were compared. In addition, the association between the annual estimates for mortality and hospitalization by age group, underlying cause of death or primary reason for admission and discharge status is discussed.

Results: The crude influenza-attributed mortality rate based on all-cause mortality and averaged over 17 influenza seasons prior to the 2009 A/H1N1 pandemic was 11.3 (95%CI, 10.5 - 12.1) deaths per 100 000 population per year, or an average of 3,500 (95%CI, 3,200 - 3,700) deaths per year attributable to seasonal influenza. The estimated annual rates ranged from undetectable at the ecological level to more than 6000 deaths per year over the three A/Sydney seasons. In comparison, we attributed an estimated 740 deaths (95%CI, 350-1500) to A(H1N1)pdm09. Annual estimates from different model parameterizations were strongly correlated, as were estimates for mortality and morbidity; the higher A(H1N1)pdm09 burden in younger age groups was the most notable exception.

Interpretation: With the exception of some of the Serfling models, differences in the ecological estimates of the disease burden attributable to influenza were small in comparison to the variation in disease burden from one season to another.

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Related in: MedlinePlus

Comparison of annual estimates of the number of hospital admissions attributable to influenza by reason for admission.Open symbols indicate that the estimate was not statistically significant (95% CI includes 0). The A(H1N1)pdm09 estimates are indicated with a red square. A linear trend line is shown in solid black.
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pone-0080481-g003: Comparison of annual estimates of the number of hospital admissions attributable to influenza by reason for admission.Open symbols indicate that the estimate was not statistically significant (95% CI includes 0). The A(H1N1)pdm09 estimates are indicated with a red square. A linear trend line is shown in solid black.

Mentions: Estimates of respiratory and circulatory influenza-attributable deaths were closely correlated (Figure 2a, b), though with the conversion from ICD-9 to ICD-10, the proportion of influenza-attributable deaths coded to other causes increased (Figure 2a, c). Annual estimates of influenza-attributed admissions were correlated by reason for admission (primary versus secondary respiratory r = 0.77, Figure 3a), as were in-hospital deaths (Figure 3b). During the pandemic, most influenza-attributable respiratory admissions had a diagnosis of pneumonia or influenza, though for seasonal influenza, annual estimates for pneumonia and influenza versus other respiratory conditions were closely correlated (r = 0.91) (Figure 3c). By broad age groups, annual estimates of influenza-attributed hospital admissions were strongly correlated between persons aged 20–64 years and persons 65 years of age or older (Figure 4a). However, the annual disease burden in persons under the age 20 years was a poorer predictor of the burden in adults (Figure 4b). Annual estimates by discharge status (discharged alive versus deceased) for persons aged 65 years or older, were also strongly correlated (r = 0.94, Figure 4c).


Estimating influenza deaths in Canada, 1992-2009.

Schanzer DL, Sevenhuysen C, Winchester B, Mersereau T - PLoS ONE (2013)

Comparison of annual estimates of the number of hospital admissions attributable to influenza by reason for admission.Open symbols indicate that the estimate was not statistically significant (95% CI includes 0). The A(H1N1)pdm09 estimates are indicated with a red square. A linear trend line is shown in solid black.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3842334&req=5

pone-0080481-g003: Comparison of annual estimates of the number of hospital admissions attributable to influenza by reason for admission.Open symbols indicate that the estimate was not statistically significant (95% CI includes 0). The A(H1N1)pdm09 estimates are indicated with a red square. A linear trend line is shown in solid black.
Mentions: Estimates of respiratory and circulatory influenza-attributable deaths were closely correlated (Figure 2a, b), though with the conversion from ICD-9 to ICD-10, the proportion of influenza-attributable deaths coded to other causes increased (Figure 2a, c). Annual estimates of influenza-attributed admissions were correlated by reason for admission (primary versus secondary respiratory r = 0.77, Figure 3a), as were in-hospital deaths (Figure 3b). During the pandemic, most influenza-attributable respiratory admissions had a diagnosis of pneumonia or influenza, though for seasonal influenza, annual estimates for pneumonia and influenza versus other respiratory conditions were closely correlated (r = 0.91) (Figure 3c). By broad age groups, annual estimates of influenza-attributed hospital admissions were strongly correlated between persons aged 20–64 years and persons 65 years of age or older (Figure 4a). However, the annual disease burden in persons under the age 20 years was a poorer predictor of the burden in adults (Figure 4b). Annual estimates by discharge status (discharged alive versus deceased) for persons aged 65 years or older, were also strongly correlated (r = 0.94, Figure 4c).

Bottom Line: To assess their robustness, the annual estimates derived from different parameterizations of the regression model for all-cause mortality were compared.In comparison, we attributed an estimated 740 deaths (95%CI, 350-1500) to A(H1N1)pdm09.Annual estimates from different model parameterizations were strongly correlated, as were estimates for mortality and morbidity; the higher A(H1N1)pdm09 burden in younger age groups was the most notable exception.

View Article: PubMed Central - PubMed

Affiliation: Centre for Communicable Diseases and Infection Control, Infectious Disease Prevention and Control Branch, Public Health Agency of Canada, Ottawa, Ontario, Canada.

ABSTRACT

Background: Poisson regression modelling has been widely used to estimate the disease burden attributable to influenza, though not without concerns that some of the excess burden could be due to other causes. This study aims to provide annual estimates of the mortality and hospitalization burden attributable to both seasonal influenza and the 2009 A/H1N1 pandemic influenza for Canada, and to discuss issues related to the reliability of these estimates.

Methods: Weekly time-series for all-cause mortality and regression models were used to estimate the number of deaths in Canada attributable to influenza from September 1992 to December 2009. To assess their robustness, the annual estimates derived from different parameterizations of the regression model for all-cause mortality were compared. In addition, the association between the annual estimates for mortality and hospitalization by age group, underlying cause of death or primary reason for admission and discharge status is discussed.

Results: The crude influenza-attributed mortality rate based on all-cause mortality and averaged over 17 influenza seasons prior to the 2009 A/H1N1 pandemic was 11.3 (95%CI, 10.5 - 12.1) deaths per 100 000 population per year, or an average of 3,500 (95%CI, 3,200 - 3,700) deaths per year attributable to seasonal influenza. The estimated annual rates ranged from undetectable at the ecological level to more than 6000 deaths per year over the three A/Sydney seasons. In comparison, we attributed an estimated 740 deaths (95%CI, 350-1500) to A(H1N1)pdm09. Annual estimates from different model parameterizations were strongly correlated, as were estimates for mortality and morbidity; the higher A(H1N1)pdm09 burden in younger age groups was the most notable exception.

Interpretation: With the exception of some of the Serfling models, differences in the ecological estimates of the disease burden attributable to influenza were small in comparison to the variation in disease burden from one season to another.

Show MeSH
Related in: MedlinePlus