“Although there are various differences between states that might have affected Covid outcomes because they all form part of one country there are enough similarities to make comparisons useful. In particular, if lockdowns are effective and necessary to prevent hundreds of thousands of extra deaths (or the equivalent for the size of the population), then those states which didn’t lock down should have a far worse death toll.”

“Our overarching goal is to minimize the spread and burden of infectious disease,” said Sara Del Valle, an applied mathematician and disease modeler at Los Alamos National Laboratory. By calculating the effects of countermeasures such as social isolation, travel bans, vaccination, and using face masks, modelers can “understand what’s going on and inform policymakers,” she said. For instance, although many face masks are too porous to keep viral particles out (or in), their message of possible contagion here! “keeps people away from you” and reduces disease spread, Del Valle said. “I’m a fan of face masks.”

"In the current outbreak, researchers are building models not only to peek into the future but also to reality-check the present. Working backwards from confirmed infections in countries other than mainland China, researchers at Imperial College London who advise the World Health Organization estimated that Wuhan had 1,000 to 9,700 symptomatic cases as of Jan. 18. Three days later, all of mainland China had officially reported 440 cases, supporting the concerns of global health officials that China was undercounting."