Health officials in San Francisco, California, said Wednesday that residents who travel outside the city during the holiday season might be asked to quarantine when they return home to prevent a surge of COVID-19 cases. 

In a statement, officials said all travelers entering the area following the holidays would be recommended to observe a two-week quarantine. Residents who interact with people from outside their homes without following social distancing guidelines and are not wearing masks will also be subjected to the 14-day quarantine. 

San Francisco health officials are still discussing with other counties in the Bay Area on whether they should issue a regional advisory. 

The move comes as the state of California has seen a surge in COVID-19 cases in recent days. Across the U.S, health officials are also recording an uptick in coronavirus cases, KTLA5 reported. 

“The last thing we need is people traveling outside to higher prevalence areas and bringing the virus back,” Martin County Health Officer Dr. Matt Willis said Wednesday. 

The decision to impose mandatory two-week quarantines aims to prevent another rise in infection in the Bay Area, which has successfully maintained a positivity rate of less than 1%. 

California has not seen a resurgence in coronavirus cases compared to other states across the nation. However, the rate of infections is rising. The state reported a seven-day average of 4,471 cases, and hospitalizations increased by at least 13.5% in the last two weeks. 

Dr. Mark Ghaly, the state’s secretary of health and human services, said California has been able to curb a resurgence after it moved businesses outdoors and slowed down its reopening. 

“Although we’re seeing some trends up here in California, those trends are modest, steady. We’re watching them closely,” Ghlay said. “I think our approach to keeping as much of our activities outdoors even in the formal business sectors as much as possible has contributed quite a bit to keeping transmission low.”

State health officials are expected to release coronavirus guidelines ahead of Thanksgiving and Christmas. 

While San Francisco has tamped down on their infection rate, two California counties on Wednesday moved backward in Governor Gavin Newsom’s reopening system as coronavirus cases rise. 

The state’s four-tier, color-coded classification system was designed to help counties determine whether they can move forward with reopening. 

The new system has four tiers: yellow, orange, red, and purple. Counties in the yellow tier have minimal coronavirus spread. Nearly all business establishments in this tier are allowed to reopen for indoor operations. They are required to impose strict guidelines, such as social distancing and face-covering. 

The purple tier means the county is seeing a widespread COVID-19 transmission. Nearly all businesses located in the area in this tier are asked to severely limit or close indoor operations. Counties with more than seven daily new coronavirus cases per 100,000 residents or a positivity rate of higher than 8% fall into this tier. 

Under the purple tier, hair salons, nail salons, and personal care services are allowed to open indoors following specific modifications. Retailers and malls may also open indoors at 25% capacity. Museums, zoos, aquariums, and movie theaters may only operate outdoors. 

Places of worship are also not allowed to hold gatherings indoors. Family entertainment centers, including mini-golf, batting cages, and go-kart racing, are required to operate outdoors. 

Under the lowest tier in California’s color-coded coronavirus system, schools and theme parks are advised to stay closed. Professional sports centers cannot take in live audiences. Non-essential offices and businesses are allowed to operate remotely, ABC News reported. 

As of Thursday, the United States has recorded 9.4 million coronavirus cases and 233,729 deaths.