California Gov. Gavin Newsom, along with Oregon Gov. Kate Brown and Washington Gov. Jay Inslee, issued a travel advisory today asking people entering or returning to the three states to self-quarantine for 14 days to help slow the spread of the coronavirus.

The advisory applies to those traveling for non-essential reasons, such as tourism or recreation, and does not pertain to those traveling for essential work, including critical infrastructure support, economic services and supply chains, urgent medical care, safety and security.

“California just surpassed a sobering threshold—one million Covid-19 cases—with no signs of the virus slowing down,” Newsom said in a Friday morning news release. “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.”

On top of the travel advisory, state health officials are also urging residents to limit interactions with other households.

On Thursday, California became the second state, behind Texas, to surpass one million cases of Covid-19. The rise in cases has prompted cities to rollback reopening plans with Sacramento, San Diego and Stanislaus counties moving back into the most restrictive tier this week—marking the highest number of counties in the purple tier since Oct. 6.

In Santa Clara County, cases are also on the rise. As of Thursday, the county of nearly 2 million people had recorded 27,299 Covid-19 cases and 440 deaths.

Local health officials last week urged residents to be diligent in slowing the spread of the virus, especially heading into the holiday and flu seasons. County Public Health Officer Dr. Sara Cody said she didn’t know what was driving the uptick in cases, but suggested it might have to do with gatherings during Halloween or “pandemic fatigue.”

“The key take-home message that I really want to get across is that what each of us do every day really matters,” Cody said. “And an increase in cases is both a risk for the health of our community as well as for the health of our economy.”