How worried should we be about the news that P1, one of the two Brazilian variants of Sars-CoV-2, has been found in six people who travelled from Brazil to Britain before the hotel quarantine rules came into force, and that one of these people has yet to be traced? Variant P1 is of concern not just because laboratory study has revealed changes to the spike protein, which might make it theoretically more transmissible, but because of real-world data from Manaus, the Amazonian city to which its origins have been traced.