I have been tracking this data daily since I first started to notice that there was a big difference in deaths between the Latitude ranges 40-50 and 50-60. I have blogged about this a couple of times, trying to understand why this might be. The range from 50-60 N. Latitude has about 80% of the Confirmed Cases per 1000 people as the hard-hit 40-50 range but only about 38% of the deaths. Countries in this 50-60 range include some of the ones who have been notable in their low numbers of deaths, such as Germany, Great Britain, Netherlands, Denmark, and Belgium. Many of these countries already appear to be “flattening the curve” on the first outbreak wave at least.
One of the big insights on death statistics from Europe at least is that 95% of the deaths across Europe from COVID-19 are in the over 65 demographic. This number appears to be more like 80% in the US, which may be part of the reason that the US death numbers are much lower than Europe. However, the 95% seems to be consistent across all European countries, so that helps us understand the demographics of the outbreak a bit better. This is a challenge, because there’s no consistency to data collection about age demographics. Most places aren’t even capturing it. It’s also hard to determine the age demographics that exist in each country. The European Union has great statistics on demographics, but doesn’t collect the actual breakdown across ages. So one thing we have going for us is that the World Bank captured the percent of the population over the age of 65 for every country on Earth. Blending this data into my COVID-19 dataset allows me to evaluate the population over the age 65 in each of these latitude belts.
Looking at the chart above raises some interesting questions. First off, we note right away that the latitude region with the greatest number of deaths (by far) does NOT have the largest number of over 65 people as we would have expected. The second interesting question is why the numbers are so much lower in the other latitude ranges (especially those above 60 degrees North and below 30 degrees North. My suspicion is that the reason is that those other latitudes have environments that are less suitable for health in old age. North of 60 degrees is really bitter cold. Maybe people move to Florida from there when they hit 65? That’s the most positive interpretation at least… Below 30 degrees has another issue — many other issues — namely, malaria.
I haven’t even opened up the latitude ranges to those south of the Equator yet, but you can see by the wide malaria zone that I don’t need to. Malaria has the greatest prevalence between 30 degrees North latitude and about -20 South latitude. Here’s a great link from the Malaria Atlas Project that shows this well. I have roughly pictured it above with the wide blue bar. Notice that there’s no overlap between the malaria zone and the red COVID-19 zone? A few possibilities exist:
- Malaria is taking susceptible people before COVID-19 can get them?
- Something about the environment where malaria flourishes is not ideal for COVID-19?
- Wait and see, maybe time will change the COVID-19 band?
Back to our discussion about the prevalence of deaths in the COVID-19 zone. We now know that the 40-50 and the 50-60 bands have roughly the same numbers of people over 65 per capita. So how do we explain the greater number of deaths in the 40-50 band? It must be that many more people over 65 are dying in this region.
Looking at the chart above (calculated using the 95% of all deaths coming from the over 65 age group) you can see that when the over 65 deaths are divided by the number of over 65 folks in each region, the 40-50 band has already lost .05% of their over 65 population. The comparison to the other regions is stark.
I’ve been thinking about why this might be happening for a few days. This is a great puzzle to me. Here are my thoughts:
- This might be coincidence. Perhaps having both Italy and Spain in the band is skewing the numbers to the bad? Maybe. But what if there is an underlying cause or sets of factors that influenced the outcomes in Italy and Spain? It’s hard to separate the two yet.
- This might be purely related to environmental factors in this region. There’s evidence that influenza virus transmission is heavily modulated by temperature and humidity. What if the COVID-19 virus’ transmission is far less effective in certain environmental conditions?
- This might be related to the success of health care strategies in the 40-50 and also 50-60 bands. Many of these countries have single-payer, Government-sponsored care. Perhaps this has been effective at extending the lives of susceptible people? Also, the lack of malaria outbreaks (as well as other tropical diseases) in the 40-60 regions has probably also extended the lives of many.
- There may be social reasons (diet, family size, elder housing, etc.) why these two regions are hardest hit (and why 40-50 is the hardest overall). This might explain why people over 65 are so much more likely do succumb to COVID-19 infections in the 40-50 region than in any other.
- Here’s my favorite. I have zero evidence for this. But… what if this virus isn’t as novel as we think and 50+ years ago a similar virus ran through the 50-60 region, where it was effective due to a seasonal environmental differential. What if there was some small built-in immunity in older people in this region that is now protecting them from COVID-19?
UPDATE: My friend Ed Beale pointed me to this article. It looks like there is a good correlation study with COVID-19 death severity and the administration of BCG, or Bacillus Calmette-Guérin, which s a vaccine for tuberculosis that is administered at birth in countries that have historically suffered from the disease, such as India. Many rich nations, such as the US, Italy and Holland, have never had a universal BCG. You might remember that my correlation study found that the number of TB cases in a country was inversely correlated with COVID-19 death rate severity. That means that countries with high TB rates had low COVID-19 death rates. More on this as I digest it.
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