Thread by @gianlucac1

WHY R0 IN ITALY/LOMBARDY IS STILL HIGH? ONE POSSIBLE REASON 3d 1/8

this 3d welcomes criticism.

Since the outbreak started, Italy adopted "quarantine at home" policy

Currently 80K mild cases are quarantined at home

The national lockdown started on the 20th of March

Since then, as work from @ciro @mtizzoni and team showed, compliance has been pretty succesful showing decrease of movements to the tune of 84%

here covid19mm.github.io/in-progress/20…

so why on earth R0 in italy/lombardia is R0 still circa 1?
2/

R0 can be represented by

Secondary Attack Rate (SAR) times Contacts

and can be broken down in 4 components
R0 Household
R0 Work
R0 Schooling
Ro Community

crossing Ciro and Michele work with google location, since the lockdown started we know that social contacts due to 3/

Schooling went to 0%
Work is circa 40%-60%
Community is circa 10%
Household is 100%

of the pre-lockdown level

Summarising, we can reasonably say R0s+R0w+R0c is down 84% vs pre-lockdown

R0h is instead unchanged.

NB the average family in Italy is 2.4 members
4/

Lets assume that R0 pre lockdown was 2.6
and R0 post lockdown (now) is circa 1

we can reasonably say that the decrease in R0 post lockdown is due almost entirely to R0w+R0s+Roc going down due to lower social contacts (84%)

So....here we go 5/

the figure show that the resulting R0 of 1 can be broken down as follows
R0h: 0,7
R0s+R0w+R0c: 0,3

IMHO R0h is still high due to quarantining infected at home.
R0w+R0s+R0c at 0.3 is what i would consider the lower R0 achievable if a State wants to keep lifeline biz open
6/

This seems consistent with Wuhan R0 pattern.
Centralized quarantine was enforced by the 1st of February.
As a consequence R0 dropped to 0.32 from 1.2

Wuhan Impact on NPI on R0 here medrxiv.org/content/10.110…

& also see 3d by @AdamJKucharski on SARh

https://twitter.com/AdamJKucharski/status/1235124781470699520?s=20

7/

I might obviously be wrong.

If not so, the point is that i dont see how R0 in Italy can go substantially below 1 if Italy keeps quarantining at home
8/8
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POST SCRIPTUM
one of the reason i might be wrong is delay in communications

so we may be seen "backlog unwinding" of infected, tests and so on.

That being true after 1 month from the lockdown, would cast lot of shadows on capacity to manage phase 2