The COVID-19 pandemic in the United States is part of the worldwide pandemic of coronavirus disease 2019 (COVID-19). Since January 2020, 44,933,336 confirmed cases have been reported with 724,317 deaths, the most of any country, and the twentieth-highest per capita worldwide. As many infections have gone undetected, the Centers for Disease Control and Prevention (CDC) estimated that, as of May 2021, there could be a total 120.2 million infections in the United States, or more than a third of the total population. COVID-19 is the deadliest pandemic in U.S. history; it was the third-leading cause of death in the U.S. in 2020, behind heart disease and cancer. From 2019 to 2020, U.S. life expectancy dropped by 3 years for Hispanic Americans, 2.9 years for African Americans, and 1.2 years for white Americans. These effects have persisted as U.S. deaths due to COVID-19 in 2021 exceeded those in 2020.On December 31, 2019, China announced the discovery of a cluster of pneumonia cases in Wuhan. The first American case was reported on January 20, and President Donald Trump declared the U.S. outbreak a public health emergency on January 31. Restrictions were placed on flights arriving from China, but the initial U.S. response to the pandemic was otherwise slow, in terms of preparing the healthcare system, stopping other travel, and testing.The first known American deaths occurred in February. On March 6, 2020, Trump allocated $8.3 billion to fight the outbreak and declared a national emergency on March 13. The government also purchased large quantities of medical equipment, invoking the Defense Production Act of 1950 to assist. By mid-April, disaster declarations were made by all states and territories as they all had increasing cases. A second wave of infections began in June, following relaxed restrictions in several states, leading to daily cases surpassing 60,000. By mid-October, a third surge of cases began; there were over 200,000 new daily cases during parts of December 2020 and January 2021.COVID-19 vaccines became available in December 2020, under emergency use, beginning the national vaccination program, with the first vaccine officially approved by the Food and Drug Administration (FDA) on August 23, 2021. Studies have shown them to be highly protective against severe illness, hospitalization, and death. In comparison with fully vaccinated people, the CDC found that those who were not vaccinated were from 5 to nearly 30 times more likely to become either infected or hospitalized. There has nonetheless been some vaccine hesitancy for various reasons, although side effects are rare. There have also been numerous reports that unvaccinated COVID-19 patients have strained the capacity of hospitals throughout the country, forcing many to turn away patients with life-threatening diseases. A fourth rise in infections began in March amidst the rise of the Alpha variant, a more easily transmissible variant first detected in the United Kingdom. That was followed by a rise of the Delta variant, an even more infectious mutation first detected in India, leading to increased efforts to ensure safety. State and local responses to the pandemic have included mask mandates, prohibition and cancellation of large-scale gatherings (including festivals and sporting events), stay-at-home orders, and school closures. Disproportionate numbers of cases have been observed among Black and Latino populations, as well as elevated levels of vaccine hesitancy, and there were reported incidents of xenophobia and racism against Asian Americans. Clusters of infections and deaths have occurred in many areas.