The "Corona crisis" calls for tough measures. These include so-called non-pharmaceutical interventions, which also include "social distancing".
Attempts to slow down the speed of the current coronavirus epidemic in Germany and the pandemic worldwide are limited to non-pharmaceutical (non-drug) measures, as we do not have any specific drugs or vaccines for the treatment or prevention of coronavirus infections. These include measures such as home quarantine, curfews, travel restrictions and "social distancing" (keeping people at a distance of about 1.5 m from each other).
Now virologists are asking themselves: Can these measures slow down the epidemic?
What have we learned from the 1918-1919 influenza pandemic?
The Spanish influenza pandemic of 1918-1919 was exceptional in its lethality (note RH: lethality is the deadliness of a disease) and the many different waves of the epidemic seen in many areas. Conservative estimates suggest that 50 million people died worldwide, causing significant social and economic disruption. However, the observations in Europe and the USA differ significantly. In Europe, only a single autumn wave was observed, while many US cities recorded two peaks in mortality just a few weeks apart. Moreover, the differences in mortality were much greater in US cities than in the UK, for example. The origin of these differences is unclear. Bootsma and Ferguson[1] have conducted modelling studies to assess the effect of the mandated non-pharmaceutical health interventions implemented in the US at the time of the Spanish influenza pandemic.
The result of their work is summarised here:
During the 1918 influenza pandemic, the US, unlike Europe, made significant efforts to improve public health. The autumn wave of the pandemic in the US was also geographically diverse compared to Europe, with some cities experiencing a single major peak in mortality and others experiencing a double peak in the epidemic. It was investigated whether differences in public health measures taken by different cities could explain the differences in epidemic patterns and observed total mortality (all-cause mortality).
Early, non-pharmaceutical interventions, "social distancing".
It could be shown that the city-specific per capita excess mortality (Note. RH: excess mortality (also excess mortality) refers to an increased number of deaths during a certain period of time compared to the mortality normally expected at the same time of year) in 1918 was significantly correlated with the per capita mortality of 1917, indicating some intrinsic variation in overall mortality (total mortality), perhaps related to socio-demographic factors. In the subset of 23 cities for which partial data on the timing of interventions were available, an even stronger correlation was found between excess mortality and the timing of the introduction of interventions in the epidemic. An adapted epidemic model for estimating the impact of the interventions for weekly mortality in 16 cities was used using almost complete data on the timing of the interventions. The model reproduced the observed epidemic patterns well. Consistent with theoretical arguments, the time-limited interventions were found to reduce all-cause mortality (all-cause mortality) only modestly (perhaps 10-30%) and the impact was often very limited because the interventions were introduced too late and lifted too early. San Francisco, St. Louis, Milwaukee and Kansas City had the most effective interventions, reducing transmission rates by up to 30-50%.
The research suggests that individuals reactively reduced their contact rates in response to high mortality during the pandemic[2].
Planning the non-pharmaceutical measures.
Also Markel and colleagues[3] have investigated whether planning during the 1918-1919 influenza pandemic regarding initiated non-pharmaceutical interventions could play a role in i) delaying the temporal impact of the pandemic, ii) reducing overall and peak infection rates, and iii) reducing cumulative deaths.
Such measures could potentially provide valuable time for the production and distribution of vaccines and antiviral drugs. Optimally, appropriate implementation of non-pharmaceutical interventions would reduce the burden on health services and critical infrastructure.
Mitigating the consequences of the pandemic.
In their research, they were able to show that the variation in mortality from city to city was related to the timing, duration and combination of non-pharmaceutical interventions, the change in population vulnerability associated with the previous pandemic waves, the distribution of age and sex, and the size and density of the population.
Markel and colleagues were able to demonstrate a strong association between the early, sustained and multi-layered use of non-pharmaceutical interventions and the mitigation of the consequences of the 1918-1919 influenza pandemic in the United States[4].
The German Medical Journal (Deutsches Ärzteblatt) also addressed the question: "COVID-19: How quarantine and other non-pharmaceutical measures slowed down the Spanish flu" in its online edition of 16.03.2020.[5].
Conclusion.
We have therefore learned that non-pharmaceutical interventions involving "social distancing" have made a significant contribution not only to slowing and mitigating the impact of the influenza pandemic, but also to significantly reducing pandemic-related mortality.
It is likely that the currently government-mandated, non-pharmaceutical interventions will also reduce the current coronavirus pandemic's burden on health services and critical infrastructure.
However, robust data on the effective containment of the coronavirus epidemic in Germany and on pandemic events worldwide can probably only be shown in the future.
References.
- 1] Bootsma MCJ, Ferguson NM. The effect of public health measures on the 1918 influenza pandemic in U.S. cities. Proc Natl Acad Sci USA 2007; 104: 7588-93 doi: 10.1073/pnas.0611071104 pmid: 17416677.
- 2] Op cit 1.
- 3] Markel H, Lipman HB, Navarro JA, Sloan A, Michalsen JR, Stern AM, et al, et al. Non-pharmaceutical interventions implemented by US cities during the 1918-1919 influenza pandemic. JAMA 2007; 298: 644-54 doi: 10.1001/jama.298.6.644 pmid: 17684187.
- 4] Op cit 3.
- [5] Medical Journal 16 March 2020. COVID-19: How quarantine and other non-drug measures have slowed down Spanish flu. https://www.aerzteblatt.de/nachrichten/111067/COVID-19-Wie-Quarantaene-und-andere-nicht-medikamentoese-Massnahmen-die-Spanische-Grippe-ausgebremst-haben?rt=d843a216383cf7b8adfaeea584f3d62e, Accessed 16 March 2020.
