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Interviewer: Professor Ben Cowling, thank you very much for
taking the time to this interview with us today to discuss
your research and findings on human movement and transmission patterns for SARS-CoV-2.
First of all, could you provide us with some background
to the research recently published in the journal
Nature Medicine, presenting the new insights into SARS-CoV-2 population transmission?
What was your initial rationale?
Prof. Cowling: I think we've all now heard of the reproductive number
or the reproductive rate for COVID, it's in the range of 2 - 3
before we start using social distancing measures in the community.
What that means is, if you take the number of cases today,
you multiply it by the reproductive number today,
that gives you an idea of how many cases there would be next week.
If we've got 1,000 cases today and our reproductive number is 2 at the moment,
it means there'll be about 2,000 cases next week.
It also means that one case is
infecting about two other people if the reproductive number is about 2.
But actually that's just an average.
What we're really looking at in this paper and the novelty of our findings, was to say:
what's the degree of variability in that?
Although on average one person infects two other people,
actually in some cases one person might not infect anyone else,
might only infect one other person.
In other cases, maybe, there are highly contagious cases.
We wanted to look at that and try to quantify it,
and that comes into 'super-spreading'.
Interviewer: You were just mentioning the term 'super-spreader event' (SSE).
Can you explain to us what is meant by that term?
What are they? How do they occur?
How does the virus take advantage of these?