San Francisco officials on Thursday announced that two residents are presumed to have tested positive for the novel coronavirus, marking the first two presumptive cases in the city.

The two patients appear to have been infected via community spread, according to Mayor London Breed's Office. They have not traveled to a location with confirmed coronavirus cases and they do not have any known contact with confirmed cases.

San Francisco Mayor London Breed announces the city's first two cases of coronavirus.

The patients are unrelated and are being cared for at separate hospitals, the mayor's office said. One is a man in his 90s who is said to be in serious condition. He has underlying health conditions. The second is a woman in her 40s who is listed in fair condition.

The San Francisco Department of Public Health lab conducted coronavirus tests for the patients and discovered positive results.

"We want everyone to remain calm and continue taking precautions to keep themselves and their families healthy," Breed said in a statement. "We have been increasing resources and staffing to prepare for the community spread of this virus, and we will do everything we can to protect public health. The City is in regular contact with all hospitals and health facilities in San Francisco, and our health system is prepared to deliver care to everyone in need and provide a coordinated response as additional cases of the novel coronavirus are confirmed."

As the new coronavirus continues to spread around the globe, people are reminded to frequently wash their hands with soap and water for at least 20 seconds, cover their coughing and sneezing, and stay home if they're sick.

The Centers for Disease Control and Prevention recommends these seven tips to help prevent the spread of COVID-19.

San Francisco's announcement comes as a cruise ship holds off the California coast to await coronavirus testing of those aboard after a passenger on an earlier voyage died and at least one other became infected.

The Associated Press contributed to this report.