Coronaviruses: the basics
Coronaviruses co-exist with humans and animals worldwide, and continuously undergo genetic mutation so that countless variants are generated (4, 5). “Nor- mal” coronaviruses are responsible for 10–20% of res- piratory infections and generate symptoms of the com- mon cold. Many infected individuals remain asympto- matic (6).
Others experience mild symptoms such as unproductive cough, whilst some additionally develop fever and joint pains. Severe illness occurs mainly in the elderly and can take a fatal course, particularly in pati- ents with pre-existing illnesses, especially of heart and lung.
Thus, even “harmless” coronaviruses can be as- sociated with case fatality rates of 8% when they gain entry to nursing homes (7). Still, due to their marginal clinical significance, costly measures for diagnosing co- ronavirus infections are seldom undertaken, searches for antiviral agents have not been prioritised, and vac- cine development has not been subject to serious dis- cussion.
Only two members of the coronavirus family reached world headlines in the past. SARS virus (official name: SARS-CoV) entered the stage in 2003. This variant caused severe respiratory illness with a high fatality rate of approximately 10%.
Fortunately, the virus turned out not to be highly conta- gious, and its spread could be contained by conventio- nal isolation measures.
Only 774 deaths were registered worldwide (8, 9). Despite this manageable danger, fear of SARS led to a worldwide economic loss of 40 billion US dollars (8). Coronaviruses subsequently faded into the background. A new variant, MERS-CoV, emerged in the Middle East in 2012 and caused life-threatening disease with an even higher fatality rate of more than 30%. But contagiousness of the virus was also low and the epidemic was rapidly brought under control (10).
China: the dread threat emerges
When the news came from China that a new corona- virus family member had appeared on stage, the most pressing question was: would it be harmless like its “normal” relatives or would it be SARS-like and highly dangerous? Or worse still: highly dangerous and highly contagious?
First reports and disturbing scenes from China caused the worst to be feared. The virus spread rapid- ly and with apparent deadly efficacy. China resorted to drastic measures. Wuhan and five other cities were encircled by the army and completely isolated from the outside world.
At the end of the epidemic, official statistics reported about 83,000 infected people and fewer than 5,000 fa- talities (11), an infinitesimally small number in a country
with 1.4 billion inhabitants. Either the lockdown worked or the new virus was not so dangerous after all. Whatever the case, China became the shining example on how we could overcome SARS-CoV-2.
More disturbing news then came from northern Italy. Striking swiftly, the virus left countless dead in its wake. Media coverage likened the situation to “war- like conditions” (12). What was not reported was that in other parts of Italy, and also in most other coun- tries, the “fatality rate” of COVID-19 was considerably lower (13, 14).
Could it be that the intrinsic deadliness of one and the same virus varied, depending on the country and region it invaded? Not very likely, it seemed.
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