“The perfect pathogen has a very long infectious period and a very long incubation period—because the longer it takes for the pathogen to declare itself, the harder it is to track,” she said. One reason measles was so wildly transmissible was that a person with it was infectious for four days before he knew he had it. This new thing felt to her a bit like that, just watching how the Chinese were reacting to it. “China was behaving like this was the perfect pathogen,” she said.
