This is an important concept:
Transmission is dependent on the number of close personal contact, not distance traveled.
- I can drive thousands of miles without meeting anyone.
- I can stay put inside a mall for a day and infect a lot of people without going anywhere else.
The aim should be reducing contacts, not travel restrictions.

Studies and data:
- Different behaviours matter
- Contact patterns (European data from several countries)
Link to NPI? There are some here.