Book excerpt: From medical expert Leana Wen, MD, Lifelines is an insider's account of public health and its crucial role—from opioid addiction to global pandemic—and an inspiring story of her journey from struggling immigrant to being one of Time’s 100 Most Influential People. “Public health saved your life today—you just don’t know it,” is a phrase that Dr. Leana Wen likes to use. You don’t know it because good public health is invisible. It becomes visible only in its absence, when it is underfunded and ignored, a bitter truth laid bare as never before by the devastation of COVID-19. Leana Wen—emergency physician, former Baltimore health commissioner, CNN medical analyst, and Washington Post contributing columnist—has lived on the front lines of public health, leading the fight against the opioid epidemic, outbreaks of infectious disease, maternal and infant mortality, and COVID-19 disinformation. Here, in gripping detail, Wen lays bare the lifesaving work of public health and its innovative approach to social ills, treating gun violence as a contagious disease, for example, and racism as a threat to health. Wen also tells her own uniquely American story: an immigrant from China, she and her family received food stamps and were at times homeless despite her parents working multiple jobs. That child went on to attend college at thirteen, become a Rhodes scholar, and turn to public health as the way to make a difference in the country that had offered her such possibilities. Ultimately, she insists, it is public health that ensures citizens are not robbed of decades of life, and that where children live does not determine whether they live.