RIO DE JANEIRO, BRAZIL - Wuhan, where the pandemic erupted, was isolated on January 23rd. The next day, 1,000 kilometers from there in the city of Canton, a man who had just arrived from Wuhan gathered his family in a restaurant. He had no symptoms but was infected with the novel coronavirus.
China's epidemiological surveillance, which maps all the movements of those testing positive for Covid-19, found that ten people from three different families who had lunch in the restaurant that day were contaminated.
However, most had no physical contact with the man - called patient A1. Nor did . . .