The court said it plans to remain open for official business and is maintaining filing deadlines in all cases, but is trying to use "remote working capabilities" to reduce the number of employees in the building. The court announced last Thursday that it was closing to public tours and visitors indefinitely.

Courtwatchers had speculated in recent days about steps the court could take to reduce the risk of transmitting the virus, particularly given the fact that several of the justices are in the elderly age group that appears to suffer the most severe effects from the highly contagious illness.

Six of the nine justices are 65 or over. Justice Ruth Bader Ginsburg is 87 and has suffered from several bouts of cancer. Justice Stephen Breyer is 81.

The court's statement announcing the delay cited historical precedents for the action, but had to reach back more than a century to find them.

The justices delayed arguments in October 1918 in response to the Spanish flu epidemic and curtailed its argument calendars in August 1793 and August 1798 in response to yellow fever outbreaks, the statement said.

The justices typically deliver their final opinions of the term by the end of June, but they are not legally required to do so. It is unclear whether and how the delay will affect opinions expected in other cases. The court can release opinions without an in-person sitting, but rarely does.

Among the opinions expected in the coming months are rulings on Trump's decision to rescind the protections for so-called Dreamers and on whether existing civil rights laws prohibit discrimination on the basis of sexual orientation.