Irish citizens in the US on certain visas are being advised to leave the country.
It comes after the number of coronavirus cases there jumped significantly.
The US became the country with the most cases in the world on Thursday.
It has had more than 90,000 positive tests as of 5.00pm on Friday - moving ahead of China, where the disease emerged back in December.
On this, the Department of Foreign Affairs says: "The spread of COVID-19 virus is becoming more serious each day, putting the population at increasing risk.
"We are advising those on short-term visas who risk losing employment, financial security and access to health care to return to Ireland."
In a travel advisory, it adds:"In the past two weeks we have advised those in the United States who wish to return home to make arrangements to do so as soon as possible."
Those who are still there are being reminded that flights continue to operate directly to Dublin from New York, Boston, Chicago and San Francisco.
In updated travel advice on Friday, Irish citizens are being told to avoid non-essential travel to the US.
The department adds: "Flight restrictions and route cancellations are happening on a daily basis worldwide and there is no guarantee that air routes will continue to operate.
"For this reason, where commercial flights are still an option, we recommend that people who wish to do so make arrangements to return to Ireland as soon as possible."