The governors of California, Oregon and Washington issued travel advisories Friday urging visitors entering their states and residents returning home to self-quarantine for two weeks to slow the spread of the coronavirus that has surged across the country.

California Gov. Gavin Newsom said the advisory comes as the state Thursday topped 1 million infections and several counties had to halt or reverse reopening businesses and activities.

“California just surpassed a sobering threshold — one million COVID-19 cases — with no signs of the virus slowing down,” Newsom said. “Increased cases are adding pressure on our hospital systems and threatening the lives of seniors, essential workers and vulnerable Californians. Travel increases the risk of spreading COVID-19, and we must all collectively increase our efforts at this time to keep the virus at bay and save lives.”

In addition to urging travelers arriving from other states or countries to self-quarantine for 14 days after arrival, the states’ advisories recommend that they limit their interactions to their immediate household.

The advisories define essential travel as travel for work and study, critical infrastructure support, economic services and supply chains, health, immediate medical care and safety and security.

“COVID-19 does not stop at state lines,” Oregon Gov. Kate Brown said. “As hospitals across the West are stretched to capacity, we must take steps to ensure travelers are not bringing this disease home with them. If you do not need to travel, you shouldn’t. This will be hard, especially with Thanksgiving around the corner. But the best way to keep your family safe is to stay close to home.”

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Washington Gov. Jay Inslee said cases of COVID-19, the disease caused by the new coronavirus, have doubled in Washington over the past two weeks, putting the state “in as dangerous a position today as we were in March.”

“Limiting and reducing travel is one way to reduce the further spread of the disease,” Inslee said. “I am happy to partner with California and Oregon in this effort to help protect lives up and down the West Coast.”