The four are in isolation while their contacts are being traced. They join three other Vatican residents who tested positive in recent weeks.

The Vatican released a brief video clip of the meeting, a clear sign both the pope and Pell wanted the reception to be seen widely.

The predominant global economic system is "unsustainable," particularly in its impact on the environment, Pope Francis said.

Dr. Anna Rowlands told America that Pope Francis "“gets populism. He gets what is the drive toward it and he rescues the notion of what it means to be ‘a people’ from the hands of the populists."

Pope Francis, who enacted new transparency laws in June covering contracts for the purchase of goods, property and services for both the Roman Curia and Vatican City State offices, welcomed the experts and said their work “is particularly dear to my heart.”

As part of our larger coverage of “Fratelli Tutti,” the latest encyclical letter from Pope Francis, America asked a number of theologians and church experts to contribute a brief response, including their perspectives on its potential impact and its particular areas of import.