Periodic Reporting for period 1 - HistoricEpi (Quantiative Study of Major Historic Epidemics and Transitions to longer, healthier lives)
Berichtszeitraum: 2015-10-01 bis 2017-09-30
Although medical historians have made great strides, little had been done to quantitatively study historical data using modern mathematical/statistical tools. As a MC professor, I undertook just that task, taking advantage of uniquely detailed Danish health data and found that the path to longevity went through broad hygiene measures that reduced childhood infectious diseases mortality. Understanding what factors drove this phenomenon will offer helpful lessons to contemporary efforts to combat these “ancient disease” outbreaks that continue to occur following disasters and in low-income settings globally.
I also studied the most serious “killer” epidemic diseases in the pre-vaccination period, including cholera, pandemic influenza. The work involved finding, digitalizing historical epidemiological data and will be used to map the phenomenon of infectious disease mortality decline. The main results of the completed or nearly completed work are as follows:
Pandemic Influenza patterns & impact, from 1889 to 2009. Our work on the 1889 “Russian” pandemic, the 1918 “Spanish” pandemic, the 1957 “Asian” pandemic and the 2009 pandemic “signature” patterns were also good illustrations of the insights that can be gained to inform pandemic preparedness going forward. Our quantitative study of weekly morbidity and mortality data for influenza and other major epidemic diseases in the 1889-1892 pandemic period led to an epidemiological demonstration of this being a pandemic event (R0>2), and that pandemic deaths occurred in the elderly and mostly in the 3rd wave. This solidifies the fact that in future pandemic events it is prudent to expect multiple waves and possible a delayed mortality impact, leaving ample time to deploy pandemic vaccine. Another lesson is that context such as background mortality levels is critical when comparing pandemic impact across age groups, time and geography. For example, in young children the pandemic mortality impact was small compared to diphtheria and diarrhea. Meanwhile, we conducted further research on the 1918 “herald wave”, and global patterns of the 1957 pandemic and saw a 1918-like age pattern in the 2009 pandemic, confirming the antigenic recycling hypothesis we had previously proposed to explain senior sparing in the 1918 pandemic. I have presented the pandemic work at several international conferences, and our 1889 manuscript was invited back by Lancet Inf Dis for publication (it will be resubmitted shortly) and our 1918 herald wave paper was accepted for publication, while the 1957 and 2009 papers were already published.
Patterns and key factors explaining the Epidemiological Transition: In Copenhagen, the road to long life expectancy was reached through sharp reductions in childhood mortality due to infectious diseases. Before 1900, more than 90% of all deaths in infants and toddlers were related to epidemic diseases like measles, diphtheria, pertussis, smallpox and diarrhea. In long morbidity and mortality time series it became clear that what happened over time was a sharp reduction in the case fatality ratio for each disease – and that this probably came about as a result of improved immune systems due to better nutrition and access to care plus social services. We are planning to study epidemiological transitions at 3 time scales: Europe 150 years ago, S.America 50 years ago and Africa now. In contemporary settings, researchers tend to attribute these reductions to biomedical interventions such as vaccines and antibiotics – but as the same pattern was observed in Europe decades before vaccines and antibiotics it is evident that other environmental and societal improvements are key determinants. This work is in progress, but already fascinating patterns emerge. Two students have completed their thesis work on this topic with me, and a comprehensive database of mortality patterns in Copenhagen during 1880-2930 is under development.