Boris Johnson self-isolating after being in contact with someone who tested positive for COVID-19

My understanding is the odds of getting it twice are pretty damned low, like there have been just a handful of cases documented globally. Is the self-isolation necessary, or just for show? My wife works with a girl who just tested poaitive for the 2nd time a few days ago. via Pocket https://ift.tt/38Yk0hR