More than half a million people have
died from COVID-19 globally. It is a major tragedy, but perhaps not on the
scale some initially
feared. And there are finally signs that the pandemic is shuddering in
places, as if its engine is running out of fuel. This has encouraged many
governments to relinquish lockdowns and allow everyday life to restart, albeit
gingerly.
The spread of SARS-CoV-2 has been difficult to predict
and understand. On the Diamond Princess
cruise ship, for example, where the virus is likely to have spread
relatively freely through the air-conditioning system linking cabins, only 20%
of passengers and crew were infected. Data from military ships and cities such
as Stockholm, New
York and London also
suggest that infections have been around 20%, much lower than earlier
mathematical models suggested.
This has led to speculation about
whether a population can achieve some sort of immunity to the virus with as
little as 20% infected, a proportion well below the widely accepted herd
immunity threshold (60-70%).
The Swedish public health authority announced in late
April that the capital city, Stockholm, was “showing
signs of herd immunity†–
estimating that about half its population had been infected. The authority had
to backtrack two weeks later, however, when the results of their own antibody
study revealed just 7.3% had
been infected. But the number of deaths and infections in Stockholm is
falling rather than increasing, despite the fact that Sweden
hasn't enforced a lockdown.
Hopes that the COVID-19 pandemic may end sooner than
initially feared have been fuelled by speculation about "immunological
dark matter”, a type of pre-existing immunity that can't be detected with
SARS-CoV-2 antibody tests............To Read More....
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