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SARS-CoV2 pandemic corona virus COVID-19 ground glass opacities epidemiology

Generally, there are two main strategies to cope with the ongoing SARS-CoV-2 pandemia (mortality 2.14% as per January 22nd (96,2 million infected patients, 2,058.534 deaths worldwide) [1,2]). 1) avoiding the transmission of the infection by isolating all individuals and cutting down social activities economy, and public life or 2. Isolating only those who are symptomatically infected, severely ill due to non-COVID-19 causes, or old. For strategy-2 three main categories of individuals need to be delineated: individuals with a clinically manifesting COVID-19 infection with or without previous morbidity, which need to be isolated (category-1); the morbid but non-COVID-19-infected ones, including the elderly, which need to be protected by isolation from becoming infected (category-2); and the asymptomatic ones which may be either infected but asymptomatic or not (category-3). These three groups should be strictly separated from each other to avoid any human-to-human transmission between the three groups.

Though most countries have adopted strategy-1 to contain the SARS-CoV-2 pandemia [1], and the vast majority of individuals strictly adhere to its rules, the pandemic spreads exponentially still in second or third wave in several countries [1]. Even in countries which declared having overcome the crisis already, flare ups are reported [3].

There are several reasons for the continuous spreading in most countries despite adherence to strategy-1. 1. too few individuals are tested. 2. too many do not adhere to separation measures. 3. transmissibility (currently estimated as 3.3-5.5 [4]) is underestimated and 4. herd immunity is not yet reached in countries in which the infection is still spreading. According to a recent news report, herd immunity of a population against SARS-CoV-2 is reached if 50-70% of the population are infected [5]. To reach herd immunity quickly, strategy-2 appears more apt than strategy-1. A further argument for strategy-2 is that mortality of SARS-CoV-2 is lower than for SARS-CoV-1 or MERS [6].

Consequently, public health authorities should not send the entire population to quarantine with all the negative consequences on psycho-social life, economy, science, art, and politics, but should rather isolate strictly categories 1-3 from each other and tolerate spreading of the disease in category-3. Strategy-2 may facilitate and speed immunisation of a population. The earlier herd immunity is reached, the earlier the pandemic will stop spontaneously as those having reached immunity will no longer get infected. Strategy-2 can be proposed as 50-75% of the infected patients remain asymptomatic and only a small portion of those who are symptomatic require hospitalisation. Increasing capacities for isolation, hospitalisation, and intensive care will be cheaper than near extinction of the world economy.