One factor I have been watching closely is the spread of the coronavirus through summer or tropical countries. For most of February, it appeared travellers brought COVID-19 to summer or tropical countries, but the spread within those countries was limited. That looks to be changing.

The raw chart comparing the two still suggests a stark difference:

But other charts are showing early negative signs:


Quick Data background

We split cases into:

  • Winter countries: Northern Hemisphere Countries currently in winter
  • Summer/Equatorial countries: Southern Hemisphere countries now in summer or Countries near the equator where temperatures are relatively high all year

The data in these charts are based on where the case was caught rather than diagnosed. For example, a case caught in Iran but diagnosed in Thailand would be assigned to winter.

All of these charts are available (updated daily) for all countries using the 'Coronavirus Dashboard' tool on our website.

Taking a turn for the worse

Signs are growing that tropical/summer countries are falling to the virus.

While the numbers are still low, they are snowballing.

And when you look through the countries, lots are showing the typical progression before cases really take off:


Scientific Background

There are suggestions that UV-B radiation and vitamin D played a role in reducing deaths in the Spanish Flu pandemic. Other studies suggest humidity greatly reduces the aerosol transmission of viruses, but some suggest humidity increases surface transmission. It is unknown how these affect COVID-19 – many experts warn against being too optimistic.

Economic Impact

There are two elements to the coronavirus:

  1. Humanitarian. The bigger the shutdowns, the greater the preventative measures, the fewer people will die.
  2. Economic. The bigger the shutdowns, the greater the preventative measures, the more significant the economic impact will be.

In the early stages, for many countries, the focus was mistakenly on minimising the economic impact. That is no longer the case. It is about preventing the spread of the disease. Or, for politicians, at least been seen to be trying. The economy is no longer the issue.

At the moment our base case is coronavirus outbreaks will be worse in colder countries. Last month, we were hoping tropical or summer countries would mostly avoid the virus, but that assumption is looking increasingly shaky.

I'm still assuming summer/tropical countries will be less affected medically. However, it is looking increasingly likely that those countries will need to enforce strict quarantines anyway. And so the economic impact may not be much better than winter countries.

Investment Outlook

The economic impact may even be worse on Southern Hemisphere countries. The natural progression of the virus combined with summer may mean the threat eases in the Northern Hemisphere over the next 2-3 months. Potentially just as the virus is receding in the Northern Hemisphere the Southern Hemisphere may get an intensification with winter that requires extended quarantines.

South-East Asia typically has increased influenza from August, so it may see the same effect.

So, caution is still the by-word.

Our impression is countries affected by SARS are dealing with COVID-19 better than those that weren't. We expect these countries will recover more quickly. 



Patrick Fresne

Although this isn't being widely reported, at current most of the countries to be worst-impacted by the COVID-19 virus are very cold countries: Switzerland, Norway, and most of all, Iceland. The media have been overlooking this because they are focusing on the total number of cases, rather than the number of cases on a per capita basis. On a per capita basis, there are more COVID-19 cases in Iceland than even in Italy. Of the major countries, Switzerland sits just behind Italy, and Norway just after Switzerland. Denmark and Estonia are not far behind. The surge in cases in these cold countries, where people spend much of their time indoors in temperature-controlled environments, surely indicates that air-conditioning has had some role to play in this pandemic. Interestingly, we see a similar pattern in wealthy, hot, equatorial countries, although it isn't quite as extreme: Singapore, Qatar and Bahrain are the 'hot' countries with the highest number of per capita cases. Of course, in these three countries, air conditioned homes and offices are commonplace. The point I am making is that the equatorial/winter paradigm seems too simplistic. Based on what I am seeing, there is a five-fold pattern with respect to the COVID-19 case numbers and climate/temperature: 1)Temperate countries, with an average annual temperature falling within the 10-20 degree Celsius band, 2) cool countries, with average annual temperatures between the 10-8 degrees band 3) cold countries below 8 degrees Celsius, and then the 4) equatorial developed countries and the 5) equatorial developing countries. The cold and temperate regions seem to be the areas most vulnerable to the coronavirus, as measured on a per-capita basis. Based on the current numbers, the equatorial developing countries don't appear to be much impacted by coronavirus so far, however in the wealthier equatorial countries, where A/C systems are common, the virus seems to be more of a problem.

Ruth Kassulke

Thanks Damien. I was thinking of looking at these patterns today and you've done the work for me. I think Patrick is right, per capita cases more relevant than total number, and air-con has a role in warmth. But even per capita cases is only a guide, because some countries are testing more e.g. South Korea, and other countries may not be testing at all.

James Bingham

I think growth rates is more important than per capita cases. You get some pretty scary numbers if you extrapolate out 10-15% growth rates for 60 days... Definitely need large scale lock downs to slow things down further than what is happening currently

Rob Garnsworthy

Think you are confused - it is probably not the season per se, it is our "behaviour" during the season. When it is cold, you are indoors more, cluster together more and therefore more likely to catch something. Versus the warmer months when the opposite is true. The proof will be the Aussie winter - will we see a spike or will the precautions taken now, work

Ruth Kassulke

Thanks for the link to the doubling rates Damien