Table 1.

Three overlapping waves of structural vulnerability related to COVID-19 among communities in the United States

Overlapping waves and approximate dates	Timeline	At-risk populations and patterns of spread	Biological vulnerability	Social vulnerability
Initial wave
January 22 to present	First case identified in Washington State	Limited community transmission	Population immunologically naive to SARS-CoV-2	Travelers from areas with active community transmission in Europe, South Korea, China, or other settings traveled to the Pacific Northwest
			Immune senescence*
				Less visible population
February 27 to present		Frail elderly individuals in nursing homes, long-term care, and assisted residential living facilities
			High prevalence of underlying chronic diseases	Insufficient medical and preventive monitoring programs at long-term care facilities and nursing homes
	First outbreak in a nursing home in Washington State†
Second wave
Early March to present	All U.S. states with COVID-19 cases by mid-March	Sustained community transmission in cities and towns with large population density	High prevalence of underlying chronic diseases such as hypertension, obesity, and diabetes mellitus	Increased frequency of exposure as day laborers or by working in the service industry with increased person-to-person interaction
				Lack of medical insurance coverage
		Underserved minorities in low-income inner-city communities (African American, Hispanics, and Native American such as Navajo Nation)		Undocumented immigrants afraid to reach healthcare system
				Documented immigrants on the path to citizenship afraid to use Medicaid under current administration policies
				Delayed lockdowns in some states
Third wave
Early April to present	Increasing number of outbreaks in prisons/jails and Immigration and Customs Enforcement (ICE) detention centers‡	Carceral settings including jails/prisons/immigration detention centers Staff, inmates, and detained individuals	Inmates in prisons and jails with high prevalence of underlying chronic diseases	Conglomerate populations in overcrowded jails and prisons

^*Individuals older than 65 years show reduced responses to vaccines and infectious diseases, including influenza.^12,15

^†From February 27 to March 25, there were approximately 140 nursing homes and long-term care facilities affected with COVID-19 cases.¹³ According to recent estimates, as of April 17, 2020, there are more than 2,500 nursing homes and long-term care facilities with reported cases.¹⁴

^‡According to the Bureau of Federal Prisons, by April 14 there were 446 cases among inmates and 248 cases among staff in 42 facilities, and 11 Residential Reentry Centers (RRCs). However, by April 9, 2020, there were 495 cases among inmates, 309 cases among staff, and 22 deaths distributed in 45 facilities, and 19 RRCs.²² When combining prisons and jails in all states, there are at least 1,324 confirmed cases of COVID-19 tied to prisons and jails, with at least 32 deaths.²³