Post by email@example.com
On Mon, 1 Jun 2020 16:38:54 +0100
Post by Robin Post by MissRiaElaine Post by firstname.lastname@example.org
Allowing individuals to decide for themselves means they are forcing
their decisions on other people. I'm fed up with the lycras around
here who've decided social distancing is unnecessary.
But it's ok for you, the government and every other Tom, Dick or Harry
to force their decisions on us. You can't have it both ways.
And the next person who utters the appalling phrase "social distancing"
will get a slap. Why can't they just say keep your distance..?
As with many such things "social distancing" started off as a term of
art among public health professionals and leaked into general usage from
them - starting many years ago.
Plus "social distancing" arguably now conveys something more specific
(in the UK, 2m) than "keeping your distance" which could more or less
depending on context - eg when drivinh on a motorway rather more than 2m*.
Social distancing in its current form was simply another method of scaring
the public. "No! Don't go near anyone, you might die!" Etc. Making people
afraid - sometimes with a visible enemy (real or fabricated), sometimes not -
so you can control their behaviour more easily is a tried and tested method of
governments down the ages. Its utterly cynical, anti democratic and I have no
time for it.
Apparently K is the new number to be concerned about.
K sheds light on the variation behind R. “Some [infectious] people might
generate a lot of secondary cases because of the event they attend, for
example, and other people may not generate many secondary cases at all,”
said Dr Adam Kucharski, an expert in the dynamics of infectious diseases at
the London School of Hygiene and Tropical Medicine.
“K is the statistical value that tells us how much variation there is in
But unlike R, K numbers are not intuitive. “The general rule is that the
smaller the K value is, the more transmission comes from a smaller number
of infectious people,” said Kucharski.
“Once K is above about five or 10 it tells you most people are generating
pretty similar numbers [of secondary cases], you are not getting these
super-spreading events. Once K is below one, you have got the potential for
Is K fixed, or does it fluctuate with public health measures, like R does?
As with the rate of transmission, there is a K value that relates to
transmission when you do not have any control measures in place. Once
measures are implemented, however, the distribution in transmission
changes. “It is unlikely that with lockdown measures in place you’d see a
lot of super-spreading events simply because there aren’t any opportunities
for them,” said Kucharski. “So if you were to analyse that data, you’d
probably calculate a different K value because you have got those control
measures changing the dynamics of interactions.”
What is the K number for Covid-19?
In the absence of public health measures, “the values that are coming out
for Covid-19 seems to be between about 0.1 and 0.5,” said Kucharski. That,
he says, means that in the early stages of an outbreak about 10-20% of
infections probably generate about 80% of the transmission.
In other words, super-spreading matters – a reality highlighted by reports
such as that from South Korea where one individual is thought to have
infected dozens of others by attending church.
But Kucharski cautioned against the use of the term super-spreader. “I
think we do have to be really careful about blaming people because often it
is not really much about the person, it is much more about the environment
they happened to be in while they were infectious,” he said.
Why is K important?
Knowing the K value helps to inform what sort of public health measures may
help to reduce R.
“If we can identify and reduce the situations that are disproportionately
driving transmission, then that suggests that we could actually have
potentially quite a lot less disruptive measures in place, but still keep
the reproduction number low,” said Kucharski.
But it could also be important for test-and-trace measures, he said. “If
cases occur at random, it’s very hard to track down and stop every chain of
transmission. But if cases cluster together, and we can identify those
clusters, testing and tracing directed at these situations could have a
disproportionate effect on reducing transmission.”
How might the relaxation of the lockdown affect K?
Lockdown reduces the chances of a single infectious person spreading the
disease to others. “Obviously if you start to allow larger gatherings, have
larger workplaces, if you have other types of interaction starting, then
that does increase the chance that one infection could spread to more
people than it would have been able to a couple of weeks ago,” said
Kucharski. “It could decrease the K, but it could also increase the R.”