  Many countries are now investigating what the effects of summer vacation
might be on the COVID-19 pandemic. Here one particular such question is
addressed: what will happen if large numbers of metropolitan people visit a
less populated province during the summer vacation? By means of a simple
epidemic model, allowing for both short and long-term visitors to the province,
it is studied which features are most influential in determining if such summer
movements will result in large number of infections among the province
population. The method is applied to the island of Gotland off the South East
coast of Sweden. It is shown that the amount of mixing between the metropolitan
and province groups and the fraction of metropolitan people being infectious
upon arrival are most influential. Consequently, minimizing events gathering
both the province and metropolitan groups and/or reducing the number of
short-term visitors could substantially decrease spreading, as could measures
to lower the fraction initially infectious upon arrival.
