Thirteen U.S. cases of the coronavirus have been confirmed and health officials said they are preparing to change their response strategy in the likely event the dreaded disease takes “a foothold in the U.S.”

U.S. health officials accidentally released an infected coronavirus patient from a San Diego hospital and blamed it on a mistake at a lab. The patient had been evacuated on a government-chartered flight from Wuhan, China, epicenter of the outbreak, CNBC reported.

The virus has so far claimed more than 1,115 lives and sickened 45,000 people, mostly in the country of origin. Nine people have been diagnosed in the U.K. About 80 percent of patients have mild cold symptoms, said Dr. Sylvie Briand, head of Infectious Hazard Preparedness for the World Health Organization during a press conference on Monday. About 15 percent of people who contract the virus end up with pneumonia and 3-to-5 percent need intensive care.

Human-to-human transmission of the coronavirus is via close contact — three-to-six feet away, CNN reported.

“At some point, we are likely to see community spread in the U.S. or in other countries,” said Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention. “This will trigger a change in our response strategy,” Messonnier told reporters on a conference call.

The CDC said it has been speaking with manufacturers of medical supplies such as face masks, to make sure there are enough if needed.

If the disease spreads in the U.S., “This will require the effort of all levels of government, the public health system and our communities as we face these challenges together,” Messonnier said. “One important aspect of this is taking steps to make sure there are enough supplies and appropriate guidance to prevent spread of the disease, especially among health care personnel caring for patients.”

Some manufacturers are reporting higher-than-usual demand for N95 respirators and face masks, Messonnier said.

“CDC does not currently recommend the use of face masks for the general public. This virus is not spreading in the community,” Messonnier said.

The CDC has monitored more than 30,000 travelers arriving in the U.S. from China since mid-January and says they did not detect any cases from returning travelers. Until now, health officials have been asking the travelers to limit their outdoor activities and monitor their own symptoms, Messonnier said.

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Messonnier said on Wednesday that U.S. health officials are implementing “additional quality controls” to ensure another patient is not released too soon.

“Our goal is to be as least restrictive as possible while ensuring the safety and health of all Americans,” she said. “We are continually reassessing our recommendations around quarantine and self-monitoring.”

The 13 confirmed cases of coronavirus in the U.S. include seven in California, two in Illinois, one in Arizona, one in Massachusetts, one in Washington state and one in Wisconsin. Two instances were known to be person-to-person transmission – one in California and one in Illinois, according to CNN.