Mass gathering events and reducing further global spread of COVID-19: a political and public health dilemma - McCloskey, Brian; Zumla, Alimuddin; Ippolito, Giuseppe; Blumberg, Lucille; Arbon, Paul; Cicero, Anita; Endericks, Tina; Lim, Poh Lian; Borodina, Maya (The Lancet (British edition), 2020)