American health authorities said Tuesday they ultimately expect the novel coronavirus to spread in the United States and are urging local governments, businesses, and schools to develop plans like canceling mass gatherings or switching to teleworking.

The comments mark a significant escalation in the level of threat being conveyed to the US public and come amid fears of a pandemic, as the disease has taken root in several countries outside China, including Iran, Italy, Japan, Singapore, South Korea, Taiwan and Thailand.

COVID-19 has killed more than 2,600 people and infected almost 80,000 others, mainly in China. There are so far 53 recorded cases in the United States.

“Ultimately, we expect we will see community spread in this country,” said Nancy Messonnier, a senior official with the Centers for Disease Control and Prevention (CDC).

“It’s not so much a question of if this will happen anymore, but rather more a question of exactly when this will happen, and how many people in this country will have severe illness.”

In the absence of a vaccine or any form of treatment for COVID-19, so-called non pharmaceutical interventions “will be the most important tools in our response to this virus” she added.

These should be decided on a case-by-case basis depending on the severity of an outbreak within localities.

“For schools, options include dividing students into smaller groups or in a severe pandemic closing schools and using internet based teleschooling.

“For adults, businesses can replace in person meetings with video and telephone conferences and increase teleworking options,” she continued, adding that on a larger scale, cities may need to cancel mass gatherings.

In the case of hospitals, it may mean delaying elective procedures and increasing telephone consultations.

“You should ask your children’s school about their plans for school dismissal or school closures. Ask about teleschooling. I contacted my local school superintendent this morning with exactly those questions.”

In a related development, the US National Institutes of Health said Tuesday it had begun its first randomized clinical trial to investigate the safety and efficacy of the antiviral remdesivir in treating COVID-19.

The first trial participant is an American who was repatriated after being quarantined on the Diamond Princess cruise ship that docked in Yokohama, Japan and who is being treated at the University of Nebraska Medical Center in Omaha.

The trial’s organizers said it will be adapted to enroll participants at other sites in the US and worldwide, eventually including up to 400 people, and would also investigate other treatments.