Since its registration late last year in China, the Covid-19 coronavirus has spread around the world and has been declared a pandemic by the World Health Organization. However, the test differences mean that the number of cases may be underestimated for some countries.
Obviously, larger countries tend to have higher numbers of cases and deaths. But there are many other factors at play, such as the demographic profiles of countries; countries with aging populations may be hit harder because the disease is more dangerous for older people.
The number of deaths is a more reliable indicator. The disease has struck some countries, including the United States, Brazil, India, Mexico and the United Kingdom with particular cruelty.
Johns Hopkins University publishes case and death data for most countries around the world (one notable exception being North Korea, which claims to have had none). But JHU admits that it collects data from many sources, some of which do not agree with each other. Even when collection is less controversial, there are significant differences in the way countries conduct testing and the way they report cases and deaths. Belgium, for example, attributes the deaths to Covid-19 if the disease is a suspected cause, even though no test has been performed.
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