Amid intensifying worldwide concern about the spread of the new coronavirus, Mayor London Breed declared a state of emergency for San Francisco Tuesday, which will ramp up the city’s efforts to prepare for and confront potential cases.

There have been no confirmed coronavirus cases in San Francisco to date, but as infections continue to rise across the world, “we need to allocate more resources to make sure we are prepared,” Breed said at a press conference announcing the emergency declaration.

“To be clear, this declaration of emergency is all about preparedness. By declaring a state of emergency we are prioritizing the safety of our communities by being prepared.”

Three people have been treated at San Francisco hospitals for coronavirus, two of which have been discharged, but to date no cases have originated inside the city.

Nine cases have been reported in the Bay Area: two from Santa Clara County residents who had traveled to Wuhan, China, the epicenter of the illness and seven people who were evacuated from a cruise ship docked in Japan. They were taken to Travis Air Force Base in Fairfield and later to Bay Area hospitals for treatment.

“Although we do not have any confirmed cases of coronavirus among San Francisco residents, we cannot afford to be unprepared if circumstances change,” said Dr. Grant Colfax, director of the city’s health department.

“Given the high volume of travel between San Francisco and mainland China and the spread of the virus to other countries, there is a growing likelihood that we will see cases in San Francisco,” he said.

Declaring a state of emergency allows San Francisco officials to marshal resources and personnel to accelerate emergency planning measures and to expand capabilities for a rapid response to a potential coronavirus case in the city. Santa Clara County declared a state of emergency a few weeks ago for similar reasons.

City employees, for example, could be redirected from their normal duties to help share critical public health information in multiple languages.

There are currently 57 confirmed coronavirus cases in the U.S.

Federal officials have imposed strict travel restrictions for people returning from mainland China, including a mandatory two-week quarantine for U.S. citizens returning from Hubei Province.

“We are prioritizing children, people who live in congregate settings (such as single-room occupancy hotels and jails) and vulnerable populations as we plan to reduce the potential for harm from the virus in the community,” Aragón said. “We have been working closely with the Chinese community, who are so impacted by this situation, and also at risk for stigma and discrimination.”

City officials urged schools to begin creating plans for potential closures, and for businesses to consider their work-from-home policies and sick leave to support anyone who needs to self-quarantine.

The emergency declaration also makes it easier for San Francisco to secure emergency state and federal funding and other resources.

The declaration comes on the heels of a troubling update from officials at the Centers for Disease Control and Prevention Tuesday, who said the United States should begin bracing for the virus to circulate more widely.

“It’s not a question of if, but when, and how many people in this country will have severe illness,” adding that the situation was moving “closer to definition of pandemic.”

The city is also expanding operations at an emergency operations center that opened nearly a month ago amid a proliferation of coronavirus diagnoses across the globe. As part of that effort, the city’s Department of Emergency Management said it planned to organize a “community branch” within the operations center to make it easier for officials to communicate and coordinate with businesses, faith-based organizations and schools.

The city’s health department has also been working with local hospitals to identify isolation rooms that can be used if diagnoses arises. Health care clinics in the city, San Francisco officials said, are also screening patients for their travel histories and screening for symptoms of the respiratory disease.

Assesor-Recorder Carmen Chu also urged the public to disavow efforts to paint the global outbreak as a “race-based virus” uniquely afflicting Chinese people and Chinese Americans.

“We have felt it in the Asian American community, when people look at someone who has coughed on the bus, when we see children in the playground and our own friends have looked at us a different way,” Chu said.

“Let’s not forget about the importance of making sure that we’re appropriately responding and that we all do our individual parts not to promote xenophobia.”

Dominic Fracassa is a San Francisco Chronicle staff writer. Email: dfracassa@sfchronicle.com Twitter: @dominicfracassa