High incidence, low case fatality rate countries

What percent of the people who get sick with pandemic flu will die? When we talk about how dangerous a virus is, this number, the case fatality rate  (CFR), is usually provided to quantify the risk. This CFR is of great interest to public health professionals and the general public for obvious reasons.

Although we are several months into the new H1N1 pandemic, we still do not have a good estimate of the CFR. Estimates vary from less than .1% (the same as seasonal flu) to 8%, three times worse than the  Spanish Influenza pandemic that devastated the world in 1918. To some extent, these differences are due to different methods of study. However, it is also possible that the CFR of the virus varies as result of environmental factors, distinct from the genetics of the virus itself.

One way to address this possibility is to compare countries with high and low CFRs. Because the initial CFR and the CFR observed after the virus has started to spread within a population may be different, I will provide the CFR for only the 20 countries with the highest incidence of the new H1N1:

  1. Brunei – 0.1%
  2. Australia – 0.3%
  3. Cayman Islands – 2.3%
  4. Chile – 0.8%
  5. New Zealand – .6%
  6. Malta – 0%
  7. Cyprus – 0%
  8. Canada – 0.56%
  9. Singapore – 0.4%
  10. Samoa – 0.0%
  11. Israel – 0.1%
  12. UK – 0.3%
  13. Panama – 0.3%
  14. Uruguay – 4%
  15. Iceland – 0%
  16. Mexico – 0.9%
  17. Costa Rica – 3.1%
  18. US – 0.9%
  19. Thailand – 0.7%
  20. Peru – 0.7%

For comparison, the worldwide average CFR is 0.8%. Three countries with a relatively high incidence of the virus had no deaths: Malta, Cyprus and Samoa. All three are small, island nations. All three had populations below 1 million. However, one of the countries with a relatively high CFR, the Cayman Islands, is also a small island country. A single death in the Cayman Islands gave it a relatively high CFR due its small population. So, we should probably disregard small countries from our analysis.

Australia and the UK are relatively large countries with relatively low CFRs: 0.3%. Costa Rica and Uruguay are moderate sized countries with relatively high CFRs: 3.1% and 4%, respectively. Although there may be multiple factors that account for the differences between these two pairs of countries, one is immediately obvious: money.

Here is the rank for each of these four countries by GDP per capita:

  • United Kingdom – 15
  • Australia – 19
  • Uruguay – 61
  • Costa Rica – 74

This wealth difference could affect CFR in a number of different ways. First, it may be that rich countries are better able to detect mild H1N1 cases. However, Uruguay and Costa Rica are both reporting a high incidence of H1N1, suggesting that these countries are testing cases aggressively. A second explanation is that rich countries offer better medical care. This is the explanation that I favor. Both the UK and Australia have been handing out Tamiflu to large numbers of people. It is not clear that Tamiflu has been given out as freely in Uruguay and Costa Rica. Further, it is reasonable to suppose that more sick people have received advanced medical care in the richer countries.

Although I believe that there are multiple variables that influence CFR, money is likely to be an important one.

So, who stands to lose the most as a result of the “Let-it-spread” policy of the World Health Organisation? Why, the poor countries, of course.

Someone should tell them.

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