Iceland is a small island nation with a thriving biotech industry. As such, it adopted a (to my knowledge) somewhat unique strategy: aside from contact tracing measure, local biotech company deCODE (an AmGen subsidiary) allows anyone who shows up to be tested. (This type of “big data” gathering seems to be part of their business model: they also did genetic testing for about half the adult population in the past https://www.decode.com/research/ )
As of the time of writing of this article https://www.businessinsider.com/iceland-coronavirus-pandemic-approach-could-help-other-countries-2020-4 about 20,930 people, i.e., 6% of the total population got tested — by far the highest proportion of tests in the population anywhere. (For perspective: to reach the same amount of coverage in the US you’d need to test about 20 million people. The US has tested about 1/20th of that number. https://covidtracking.com/data/ )
As of this morning, Iceland has 1,319 cases, of which 4 (four) people have died, 44 people are hospitalized (12 of them in ICU), and 1,031 are in home isolation. 284 have recovered from the infection. 7,166 people are currently in quarantine, 8,945 have completed quarantines.
Now beware of comparing apples with oranges: the official government COVID19 page for Iceland https://www.covid.is/data speaks of 1,319 infections, not sick people. (It appears Israel similarly counts everybody who tests positive as a patient.) So the apparent enviably low 4/1319*100%=0.3% is really an IFR (infection fatality rate), not a CFR (case fatality rate).
[Iceland’s chief epidemiologist Thorolfur] Guðnason is quoted here
https://futurism.com/neoscope/half-coronavirus-carriers-no-symptoms as saying “Early results from deCode Genetics indicate that a low proportion of the general population has contracted the virus and that about half of those who tested positive are non-symptomatic.”.
Note, Iceland did not engage in any lockdowns — gatherings over 25 are forbidden, but otherwise economic life goes on. Instead, aggressive test & trace and quarantines are the order of the day. While the country’s low population density might seem to help, nearly two-thirds of the population is concentrated in and around the capital Reykjavik — which especially by US standards is fairly dense.
Elsewhere I read that not only was Iceland able to trace the source of the infection in most cases, but even to distinguish between different mutants of the virus. https://edition.cnn.com/2020/04/01/europe/iceland-testing-coronavirus-intl/index.html
“We can determine the geographic origin of the virus in every single [virus] in Iceland,” he said, adding there are specific, minor mutations for the virus that came from Italy, Austria and the UK. “There was one that is specific to the west coast of the United States,” [Stefansson] added.
[He] wonders whether mutations in the virus are “responsible, in some way, for how differently people respond to it — some just develop a mild cold, while some people need a respirator,” or whether a person’s genetics dictates their condition. “Or is it a combination of these two?” he asks.
“Keep in mind that the screening is now randomized, but voluntary so there is some bias in the data,” the Directorate of Health said in a statement, adding that a “randomized screening program has started and a blood serum screening for antibodies is planned.