Published Online 8 April 2009.
{snips}
We pointed out that there was a clear north/south gradient, but did not find a rationale for this gradient. All factors that can be related to the mortality burden such as the existence of co-infectious diseases, especially bacterial pneumonia and tuberculosis, or socio-economic status were unlikely to have a north/south gradient.
Possible geographic determinants of the influenza mortality are cold temperature and vitamin D deficiency relative to low sunlight exposure, but they would have implied a higher mortality in northern countries, not the opposite as we observed.
---------------------------
Conclusions
During the Spanish flu, the excess mortality was 1.1% of the European population. Our study highlights the synchrony of the mortality waves in the different countries, which pleads against a European origin of the pandemic, as was sometimes hypothesized.
Background
The origin and estimated death toll of the 1918-1919 epidemic are still debated. Europe, one of the candidate sites for pandemic emergence, has detailed pandemic mortality information.
Objective
To determine the mortality impact of the 1918 pandemic in 14 European countries, accounting for approximately three-quarters of the European population (250 million in 1918).
Methods
We analyzed monthly all-cause civilian mortality ratesin the 14 countries, accounting for approximately three-quarters of the European population (250 million in 1918). A periodic regression model was applied to estimate excess mortality from 1906 to 1922. Using the 1906-1917 data as a training set, the method provided a non-epidemic baseline for 1918-1922. Excess mortality was the mortality observed above this baseline. It represents the upper bound of the mortality attributable to the flu pandemic.
Results
Our analysis suggests that 2.64 million excess deaths occurred in Europe during the period when Spanish flu was circulating. The method provided space variation of the excess mortality: the highest and lowest cumulative excess - predicted mortality ratios were observed in Italy(+172%) and Finland (+33%). Excess-death curves showed high synchrony in 1918-1919 with peak mortality occurring in all countries during a 2-month window (Oct-Nov 1918).
----------------------------------------------------------------------
{other points of interest}
Excess mortality was found to be strongly country dependent.
The cumulative excess-predicted mortality ratio:
Italy (+172%)
Bulgaria and Portugal (+102% each)
Spain (+87%)
Netherlands (+84%)
Sweden (+74%)
Germany (+73%)
Switzerland (+69%)
France (+66%)
Norway (+65%)
Denmark (+58%)
Scotland (+57%)
England and Wales (+55%)
Finland (+33%)
The highest excess-mortality rate (per 10 000 inhabitants) cumulated throughout the entire excess-mortality period was observed in Portugal(233/10 000 inhabitants), followed by Italy, Spain, Bulgaria, Switzerland, Finland, France, Germany, Sweden, Netherlands, Norway, England and Wales, Scotland and Denmark.
Overall, the excess mortality found during the pandemic was 3.5 times higher than the excess mortality found in the rest of the 1906-1922 period. This ratio ranged between 1.6 (Finland) and 6.1 (Portugal).
We found a statistically significant negative correlation between excess mortality and latitude, meaning that northern countries experienced significantly less mortality, while Southern Europe suffered significantly more excess deaths. No relationship between excess mortality andlongitude was observed.
Countries were clustered according to their mortality patterns:
# one sharp mortality peak (e.g. Portugal, Spain, Italy, Bulgaria),
# countries with two major peaks (e.g. Switzerland, Scotland, Netherlandsand France)
# country with several successive peaks (only Finland).
Excess mortality was time dependent: the start and stop months of the excess-mortality period varied across the continent and occurred in four waves. Moreover, an early first wave of deaths, occurring between March 1918 and July 1918, was observed in six countries (Bulgaria, Portugal, Germany, Finland, Switzerland and Spain).
Importantly, the excess death curves could be temporally superposed, albeit not of the same intensity, for 1918-1919, with mortality peaking in all countries within a 2-month window (October-November 1918), defined as the second wave. In five countries (Spain, Denmark, Finland, Germany and Switzerland), a late peak between January 1920 and April 1920 was recorded. That fourth wave in 1920 was not taken into account in estimating the cumulative excess-death rates for the entire pandemicperiod.
American excess deaths during the same period were estimated at 550,000 (corresponding to 0.65% of the American population) by Glezen WP. However, Johnson-Mueller put the US figure at 675,000 deaths and more recently Murray et al. at only 400,000 deaths (0.47% of the total population).
There was a high level of variability between the excess of mortality experienced in the 14 countries we studied, with a minimal value of 33% in Finland and a maximal value of 172% in Italy.
http://www3.interscience.wiley.com/cgi-bin/fulltext/122313738/HTMLSTART
{snips}
We pointed out that there was a clear north/south gradient, but did not find a rationale for this gradient. All factors that can be related to the mortality burden such as the existence of co-infectious diseases, especially bacterial pneumonia and tuberculosis, or socio-economic status were unlikely to have a north/south gradient.
Possible geographic determinants of the influenza mortality are cold temperature and vitamin D deficiency relative to low sunlight exposure, but they would have implied a higher mortality in northern countries, not the opposite as we observed.
---------------------------
Conclusions
During the Spanish flu, the excess mortality was 1.1% of the European population. Our study highlights the synchrony of the mortality waves in the different countries, which pleads against a European origin of the pandemic, as was sometimes hypothesized.
Background
The origin and estimated death toll of the 1918-1919 epidemic are still debated. Europe, one of the candidate sites for pandemic emergence, has detailed pandemic mortality information.
Objective
To determine the mortality impact of the 1918 pandemic in 14 European countries, accounting for approximately three-quarters of the European population (250 million in 1918).
Methods
We analyzed monthly all-cause civilian mortality ratesin the 14 countries, accounting for approximately three-quarters of the European population (250 million in 1918). A periodic regression model was applied to estimate excess mortality from 1906 to 1922. Using the 1906-1917 data as a training set, the method provided a non-epidemic baseline for 1918-1922. Excess mortality was the mortality observed above this baseline. It represents the upper bound of the mortality attributable to the flu pandemic.
Results
Our analysis suggests that 2.64 million excess deaths occurred in Europe during the period when Spanish flu was circulating. The method provided space variation of the excess mortality: the highest and lowest cumulative excess - predicted mortality ratios were observed in Italy(+172%) and Finland (+33%). Excess-death curves showed high synchrony in 1918-1919 with peak mortality occurring in all countries during a 2-month window (Oct-Nov 1918).
----------------------------------------------------------------------
{other points of interest}
Excess mortality was found to be strongly country dependent.
The cumulative excess-predicted mortality ratio:
Italy (+172%)
Bulgaria and Portugal (+102% each)
Spain (+87%)
Netherlands (+84%)
Sweden (+74%)
Germany (+73%)
Switzerland (+69%)
France (+66%)
Norway (+65%)
Denmark (+58%)
Scotland (+57%)
England and Wales (+55%)
Finland (+33%)
The highest excess-mortality rate (per 10 000 inhabitants) cumulated throughout the entire excess-mortality period was observed in Portugal(233/10 000 inhabitants), followed by Italy, Spain, Bulgaria, Switzerland, Finland, France, Germany, Sweden, Netherlands, Norway, England and Wales, Scotland and Denmark.
Overall, the excess mortality found during the pandemic was 3.5 times higher than the excess mortality found in the rest of the 1906-1922 period. This ratio ranged between 1.6 (Finland) and 6.1 (Portugal).
We found a statistically significant negative correlation between excess mortality and latitude, meaning that northern countries experienced significantly less mortality, while Southern Europe suffered significantly more excess deaths. No relationship between excess mortality andlongitude was observed.
Countries were clustered according to their mortality patterns:
# one sharp mortality peak (e.g. Portugal, Spain, Italy, Bulgaria),
# countries with two major peaks (e.g. Switzerland, Scotland, Netherlandsand France)
# country with several successive peaks (only Finland).
Excess mortality was time dependent: the start and stop months of the excess-mortality period varied across the continent and occurred in four waves. Moreover, an early first wave of deaths, occurring between March 1918 and July 1918, was observed in six countries (Bulgaria, Portugal, Germany, Finland, Switzerland and Spain).
Importantly, the excess death curves could be temporally superposed, albeit not of the same intensity, for 1918-1919, with mortality peaking in all countries within a 2-month window (October-November 1918), defined as the second wave. In five countries (Spain, Denmark, Finland, Germany and Switzerland), a late peak between January 1920 and April 1920 was recorded. That fourth wave in 1920 was not taken into account in estimating the cumulative excess-death rates for the entire pandemicperiod.
American excess deaths during the same period were estimated at 550,000 (corresponding to 0.65% of the American population) by Glezen WP. However, Johnson-Mueller put the US figure at 675,000 deaths and more recently Murray et al. at only 400,000 deaths (0.47% of the total population).
There was a high level of variability between the excess of mortality experienced in the 14 countries we studied, with a minimal value of 33% in Finland and a maximal value of 172% in Italy.
http://www3.interscience.wiley.com/cgi-bin/fulltext/122313738/HTMLSTART
uring 1918 Finland was embroiled in a civil war - the above record of fatalities might be less than accurate.