U.S. health officials on Friday said they are preparing for the possibility of the spread of the new coronavirus through U.S. communities that would force closures of schools and businesses.

The United States has yet to see community spread of the virus that emerged in central China in late December. But health authorities are preparing medical personnel for the risk, Nancy Messonnier, an official with the Centers for Disease Control and Prevention (CDC) told reporters on a conference call.

In coming weeks, if the virus begins to spread through U.S. communities, health authorities want to be ready to adopt school and business closures like those undertaken in Asian countries to contain the disease, Messonnier said.

“We’re not seeing community spread here in the United States yet, but it’s very possible, even likely, that it may eventually happen,” Messonnier said.

“Our goal continues to be to slow the introduction of the virus into the U.S. This buys us more time to prepare communities for more cases and possibly sustained spread.”

The CDC is taking steps to ensure frontline U.S. healthcare workers have supplies they need, she added, by working with businesses, hospitals, pharmacies and provisions manufacturers and distributors on what they can do to get ready.

The World Health Organization has warned that the window of opportunity to contain the international spread of the epidemic that has killed more than 2,200 people was closing, as the virus has spread to some 26 countries with a large cluster in South Korea and recent outbreaks in Iran, Lebanon and Italy

“If we do well, we can avert any serious crisis, but if we squander the opportunity then we will have a serious problem on our hands,” WHO chief Tedros Adhanom Ghebreyesus said in Geneva.

The United States currently has 13 cases of people diagnosed with the virus within the country and 21 cases among Americans repatriated on evacuation flights from Wuhan, China, and from the Diamond Princess cruise ship in Japan, CDC said.

​Of 329 Americans evacuated from the cruise ship, 18 tested positive for the virus. Eleven of them are at University of Nebraska Medical Center, five are in medical facilities near Travis Air Force Base in California and two are near Lackland Air Force Base in San Antonio, Texas.

The CDC is still handling the bulk of testing for the coronavirus as it works out issues with test kits sent to states, Messonnier said.

Only three U.S. states currently have the capacity to run tests for the virus locally, the Association of Public Health Laboratories (APHL) told Reuters on Friday.