What is already known about this topic?“The extensive travel from Europe, once Europe was having outbreaks, really accelerated our importations and the rapid spread,” Dr. Schuchat told the AP. ”I think the timing of our travel alerts should have been earlier.”
The first confirmed coronavirus disease 2019 (COVID-19) case in the United States was reported on January 21, 2020. The outbreak appeared contained through February, and then accelerated rapidly.
What is added by this report?
Various factors contributed to accelerated spread during February–March 2020, including continued travel-associated importations, large gatherings, introductions into high-risk workplaces and densely populated areas, and cryptic transmission resulting from limited testing and asymptomatic and presymptomatic spread. Targeted and communitywide mitigation efforts were needed to slow transmission.
What are the implications for public health practice?
Factors that amplified the March acceleration and associated mitigation strategies that were implemented can inform public health decisions as the United States prepares for potential re-emergences.
Continued introductions of SARS-CoV-2 from outside the United States contributed to the initiation and acceleration of domestic COVID-19 cases in March. After Chinese authorities halted travel from Wuhan and other cities in Hubei Province on January 23, followed by U.S. restrictions on non-U.S. travelers from China issued on January 31 (effective February 2), air passenger journeys from China decreased 86%, from 505,560 in January to 70,072 in February. However, during February, 139,305 travelers arrived from Italy and 1.74 million from all Schengen countries,* where the outbreak was spreading widely and rapidly. Travelers from Italy and all Schengen countries decreased 74% to 35,877 and 50% to 862,432, respectively, in March.† Genomic analysis of outbreak strains suggested an introduction from China to the state of Washington around February 1.§ However, examination of strains collected from northern California during early February to mid-March indicated multiple introductions resulting from international travel (from China and Europe) as well as from interstate travel.¶ Sequencing of strains collected in the New York metropolitan area in March also suggested origins in Europe and other U.S. regions.** Returning cruise ship travelers also contributed to amplification during this time (3). Persons from many countries are in close contact on cruises, and crew members continue to work on ships for multiple voyages. As a result, passengers returning from cruises contributed to the early acceleration phase. For example, 101 persons who had been on nine separate Nile River cruises during February 11–March 5 returned to 18 states and had a positive test result for SARS-CoV-2, nearly doubling the total number of known COVID-19 cases in the United States at that time (Figure 2).
Saturday, May 2, 2020
Missed Opportunities to Slow the Spread
Anne Schuchat has an article at MMWR titled "Public Health Response to the Initiation and Spread of Pandemic COVID-19 in the United States, February 24–April 21, 2020." The author is Principal Deputy Director of the Centers for Disease Control and Prevention.