Charting COVID-19 by country: Early actions reap big rewards
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Updated with the latest case and death numbers as of 10 May 2020
After a long and tight lockdown in Wuhan, the city has begun to crack open its doors in a welcome, if hesitant, relief. Many other parts of the world are still in the height of the crisis, hoping for a light at the end of the tunnel and considering a speedier exit strategy. Still others are just beginning to climb the curve.
The rapidly changing dynamics of this invisible enemy and its march around the world cut across many political and social dimensions. All raise the important question of timing. What's the best, most effective time for interventions to begin – and eventually – to be lifted? What's realistic? What's safe? What's practical?
There are no clear answers, but we can draw insights by comparing the magnitude of the spread and growth in cases and deaths across each country and testing their relative success against the invisible viral enemy. This analysis will help give a sense of when things are likely to return to some semblance of normalcy. It also offers insights into the timing and intensity of actions for those countries, provinces and states just beginning the battle to control the virus's spread.
Using a common "time zero" for comparison purposes
Drawing accurate comparisons across countries is difficult as each one started programs of social distancing, lock downs and aggressive testing at different times and with varying degrees of intensity. This makes it harder to understand the magnitude of the spread by country and a country's relative success in the fight against the virus
To give more meaningful comparison and insights, it's helpful to plot the progress from a common "time zero" event. For purpose of our analysis, we established a common time zero event as the date when cumulative deaths exceeded 10 or cumulative cases exceeded 100. This presents a more revealing picture.
The plots used are based on the number of cases and deaths as of 10 May 2020.
Many Western nations underestimated the benefits of strong early interventions
In our analyses, we focus on eight countries: US, UK, China, France, Spain, Italy, Japan and South Korea. We consider Hubei Province separate from all of China because using the overall picture for China leads to some distortions as the pandemic was very well controlled outside of Hubei Province.
We selected the most informative graphs in the series below which tell an interesting story:
- Countries that adopted early and comprehensive measures clearly controlled both the magnitude of the disease and shortened the overall time from the peak to having a manageable, small number of cases. These measures included social distancing and lockdowns, sometimes in conjunction with contact tracing and isolation.
- Among the countries selected, Japan and South Korea are notable exceptions in that they managed to control the spread from its very beginning due to Japan implementing strict control measures and South Korea's extensive testing program in conjunction with controls early on. Japan has seen increased growth rates of deaths beginning of April, since they relaxed their lockdown (see figure 2). These growth rates are still much lower than in Western countries.
Figures 1 and 2: Absolute progression is faster outside China (except for Japan and South Korea)
First, we look at the progression of the absolute number of cumulative deaths across countries. Figure 1 shows the progression has been much faster in all countries compared to China (blue line)/ Hubei (red dash) with notable exceptions of Japan (green line) and South Korea (purple line). This also illustrates how much higher the death count is in Western nations compared to China, plus that the number of deaths continued to climb dramatically, well after the period from time zero when China began to see the number of deaths level off.
The black dots represent the date when lock downs or stringent social distancing measures or "interventions" were imposed. The US (red line) individually initiated interventions quite late compared to other which likely means a continued steep increase in the number of deaths over the coming weeks.
The conclusion is that the strictness of the early measures in China and the extensive testing clearly helped control the pandemic. South Korea and Japan are excellent examples where social distancing measures and -- for South Korea in particular -- stringent testing, contact tracing and isolation measures helped to keep the virus at bay.
Figure 1: Comparative of number of cumulative deaths, time zero = 10 cumulative deaths
These conclusions are even more apparent by plotting the log of the number of deaths. Log plots are useful to depict the rate of growth. The steeper the curve, the faster the growth. In figure 2, we can see that Spain (blue dash) appears to have had the fastest growth to date, with UK (green dash) a close second and Italy (orange line) and France (orange dash) vying for third. The US experienced a slow growth rate initially (probably due to limited testing) but has picked up pace and is currently experiencing the fastest growth rates among this set of countries. Between the testing policy and the timing of interventions, several Western nations are lagging behind Eastern nations in controlling the pandemic at similar stage in the pandemic's evolution.
Figure 2: Comparative of log plot of number of cumulative deaths, time zero = 10 cumulative deaths
Figure 3: Death rates in European countries are lagging the experience of Hubei Province
It is also helpful to understand the growth in "death rate" from the virus, which expresses the deaths per 100 million of population. For this, we look at the log plot of cumulative cases per 100 million. This plot shows the Hubei Province death rate has been much higher than overall China mortality, proving that interventions and the lockdown, along with contact tracing, effectively contained the pandemic within the Hubei Province, while in Hubei itself early opportunities to contain the spread were missed.
Figure 3 shows the death rate in Spain (blue dash) is currently the highest of the selected countries/regions, closely followed by Italy (orange line). UK (green dash) and France (orange dash) have got less notice than Italy, but it appears that the death rates are at the same level as Italy .
Hubei's death rate (red dash) began to level off at about 25 days from time zero, but Western nations still exhibit an increasing rate. With 61 million people, Hubei Province is a good comparative to other European countries.
Figure 3: Comparative of number of cumulative deaths per 100 million, time zero = 10 cumulative deaths
Figure 4: Observed cases per 100 million of population shows Western nations clearly faring worse
Looking at case rates (in addition to deaths) per 100 million can also be insightful. We see the growth in case rates in Western nations has exceeded that of East Asian countries at the same phase for a while now, and at present all observed Western nations in this study have exceeded Eastern nations – and Hubei – in case count per million.
Note that there might be substantial differences between reporting of cases due to limited testing capacity and variance in testing strategies (for example broad population wide testing in Iceland or testing of at-risk population in the Netherlands). The time series for deaths, shown next, are therefore considered much more reliable to draw conclusions on the effectiveness of the control measures.
Figure 4: Comparative of cumulative cases per 100 million, time zero = 100 cumulative cases
Figures 5 & 6: Case and death rates slowing as social distance breaks the spread
A plot of the 5-day moving average of the increase in cases does show some positive news. Though the new number of cases and deaths continue to be quite high, the rate of growth has come down in most countries. The US (red line) is still leading with new case growth rates, but the overall growth rate appears to have hit a peak several days ago, as has the case growth rate for all other countries except UK. This is a direct indication of the success of the intervention methods such as social distancing, school closings, lockdowns and other measures implemented in states where the virus hit the hardest.
UK (green dash) rate is still increasing in both case counts and death counts - this is of concern.
Most countries went into lockdown soon after case counts exceeded 100 and deaths exceeded 10. US is a notable outlier, so the growth rate in cases and deaths hit a peak later due to the relative delay in deploying state-by-state interventions. The relative daily increase of deaths is insightful as it shows that countries need to keep up their efforts to get to where Hubei Province in China stood at 60 days post lockdown.
This will likely prolong the period for which the interventions and suppressed business activity will continue. Italy and South Korea are especially interesting. After more than a month in lockdown, Italy is on the right path but again will have to maintain its resolve for some time to get to near zero growth in case and deaths like East Asian nations.
Figure 5: Moving average of relative daily increase in cumulative cases, time zero = 100 cases
Figure 6: Moving average of relative daily increase in cumulative deaths, time zero = 10 deaths
The virus must be tackled early with strength and continuous determination to blunt its destruction
The message from these charts is clear: social distancing, lockdowns, travel restrictions and other actions in conjunction with widespread testing early in the pandemic blunt its speed and magnitude effectively.
It's reasonable to conclude that the earlier this is done, the sooner the pandemic will run its course, and the sooner business activity can resume. Western nations that missed these early opportunities to control the pandemic, are paying a steeper price than East Asian nations in case and death counts and may also have a longer period of economic activity slowdown.
As the economic damage mounts, political pressure to remove restraints is rising quickly. As countries get closer to the point at which China started easing its restrictions, they have to think of how to manage recurring outbreaks. Here South Korea continuously managed the spread by a strict testing, contact tracing and case isolation regime. A key measure to consider is when to lift travel restrictions. We have seen that in many Asian countries, an easing of travel restrictions triggered a minor recurrence. What is the best path for Western nations to continue to limit the impact of the disease, and can they take a similar path to East Asian nations to continously manage through contact tracing, limiting travel and other control measures?
Clearly a population-wide testing strategy will be essential to understand the true infection rate and an important building block to restore economic activity while we await a vaccine. We covered an update on vaccine development here, and our next L&H Trend Spotlight will provide a similar overview for pharmaceutical treatments. Stay tuned.