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The coronavirus pandemic has made its way across the United States, but one of the most striking instances remains how swiftly and dangerously the virus spread in Seattle-area long-term care facilities beginning in February. The Centers for Disease Control and Prevention now seems to have a clearer idea of how that happened.

Most of Seattle's nursing home cases are connected to a facility in Kirkland, Washington, but the CDC found in a report published Wednesday that by March 9, at least eight other nursing and assisted living facilities had reported one or more cases of COVID-19.

The investigation concluded that the spread seems to be the result of multiple factors, including staff members who worked while symptomatic; staff members working in more than one facility; unfamiliarity with precautionary standards; inadequate infection control supplies; and delayed recognition of cases because staff members weren't aware of what they were dealing with at the time.

Those findings, the CDC said, show COVID-19 can be particularly damaging in long-term care facilities where the population is already more vulnerable to the virus because of the average age and greater likelihood of underlying conditions among residents. The report determined it's critical such facilities across the U.S. "implement active measures to prevent the introduction of COVID-19." Read the full report here.