Analysis by Keith Rankin.
The above chart shows my estimates for the actual infection rates of Covid19 for all countries with an (estimated) infection rate of above four percent of their population. Plus, Australia and New Zealand.
The principal method of estimation is to use the testing ‘positivity rate’. If the average positivity rate over the last week is 10% of test undertaken, then my estimate will be 2.5% of the country’s population, plus existing notified cases. (The exceptions are United Kingdom, Belgium, Andorra and San Marino – where most of the cases are ‘recovered’ – and which have high proportions of elderly people in their populations. For these cases, I divided the notified deaths by 1.5%, the likely case fatality rate in these countries.)
The highest (estimated) infection rates are mostly in Latin America and Arabia. The worst of these countries (Haiti to Mexico) have done comparatively little testing, and have positivity rates close to 50%. For these, the estimates may come down with more information.
We also note that Pakistan and Bangladesh most likely have higher infection rates than India.
Of particular concern to us in New Zealand is Qatar, which appears to have a 10% infection rate, and that could be an understatement. Many people flying into New Zealand are coming via Qatar, presumably on Qatar Airways flights. This includes New Zealand’s latest two Covid19 cases, who flew via Doha. If any country gains ‘herd immunity’, it may well be Qatar. But now, it is highly infectious with more notified daily new cases – per capita – than anywhere else; and Qatar has been in this situation for some time.
All passengers coming into New Zealand transiting in Doha should automatically be treated as likely Covid19 suspects. New Zealand officials should have been alerted to this.
Another country of much concern is Panama – an international financial centre – which is only just starting to take testing seriously, and has positivity rates close to 40% of tested people.
Like Panama, Sweden has only taken testing seriously in recent weeks, and still has 15% positivity rates. On this basis, I am estimating Sweden’s actual infection rate to be 7.5 times its notified rate. This still only leaves 4.26% of Swedes infected, suggesting that Sweden will fall short of attaining herd immunity. The main issue here though, may be that many people testing negative in Sweden had Covid19 in March. So my sense is that Sweden will end up with 10% of its population eventually having the disease.
While the United Kingdom has an estimated present 4.1% infected, over the last week less than one percent of people tested returned positive results. So we can conclude that 95% of Brits do not have Covid19.
We may note that New Zealand has a total estimated infection rate of 0.03%, and Australia has 0.04%. We may also note that Uruguay, a country sandwiched between Brazil and Argentina, has a set of statistics much like New Zealand. I estimate that they have a 0.05% present infection rate, compared to 8% in Brazil.