RICHMOND — Gov. Ralph Northam and his wife, Pamela Northam, announced Friday that they both tested positive for the novel coronavirus and plan to isolate for 10 days in the governor's mansion, where he will continue working as the state's chief executive.

Northam (D) is experiencing no symptoms and the first lady’s are mild, his office said.

The two were tested Thursday after learning the night before that “a member of the Governor’s official residence staff, who works closely within the couple’s living quarters, had developed symptoms and subsequently tested positive for COVID-19,” according to a news release from Northam’s office. “Both the Governor and First Lady received PCR nasal swab tests yesterday afternoon, and both tested positive.”

Northam, 61, a former Army doctor and pediatrician, has required Virginians to wear masks inside public spaces during the pandemic. He also has urged frequent hand-washing and social distancing.

“As I have been reminding Virginians throughout this crisis, #COVID19 is very real and very contagious,” he tweeted Friday. “We are grateful for your thoughts and support, but the best thing you can do for us — and most importantly, for your fellow Virginians — is to take this virus seriously.”

Northam also tweeted that he was still working, just remotely, from the governor’s mansion.

The governor’s mansion and Northam’s offices in the Patrick Henry Building were closed for the day for “deep cleaning,” according to a statement from his office. It also said the Northams were working closely with the state and Richmond health departments to trace their close contacts.

The Executive Mansion staffer who tested positive had not been hospitalized, according to Northam’s office, which declined to provide more details about that person’s condition or duties at the mansion, citing privacy concerns.

Northam has tried to chart a nuanced path through the pandemic, imposing strict restrictions early on to try to contain the virus while easing up in some areas ahead of neighboring Maryland and D.C.

In March, Northam was the second governor nationally to shutter schools for the remainder of the academic year. In May, he ordered Virginians to wear masks in indoor public spaces such as stores. Critics who resented the mandate blasted him for appearing just days earlier in Virginia Beach, where he mingled maskless with visitors outdoors on the boardwalk. He acknowledged that he should have been carrying a mask in case he ended up in a crowd.

In public appearances such as news briefings on the virus, Northam wears a mask, removing it only when he steps up to a lectern to speak. His staff says he always wears one while working in the office and traveling. Pamela Northam, a former science teacher who has been promoting early-childhood education around the state, observes the same precautions.

Ralph Northam is one of several governors to have tested positive. Missouri Gov. Mike Parson (R) announced Wednesday that he and his wife, Teresa, have tested positive for the coronavirus. Parson said in a recorded message that he had no symptoms and the first lady’s were mild.

Parson, 65, has often resisted calls for tough restrictions during the pandemic. He has encouraged Missourians to wear masks but, like 15 other governors, has not mandated their use. In July he tweeted photos of himself without a mask at an indoor event, where he stood close to people.

Oklahoma Gov. Kevin Stitt (R), another governor who has not mandated masks, tested positive for the virus in July. Hawaii Lt. Gov. Josh Green (D) announced Sept. 12 that he’d tested positive for the coronavirus.

The virus, which is easily spread from person to person, has a relatively long incubation period and an unusually large proportion of people infected with it have no symptoms, according to the Centers for Disease Control and Prevention.

Northam’s announcement prompted several lawmakers to seek testing. Dels. Danica A. Roem (D-Prince William) and Elizabeth R. Guzman (D-Prince William) tweeted Friday night that they got tested since they were at an event with Pamela Northam. The Hampton mayor and council also sought testing because the governor had visited earlier in the week for an economic development announcement.

Hampton Mayor Donnie Tuck said he and other participants wore masks while appearing with Ralph Northam at the event on Tuesday, removing them only to make their remarks from a shared microphone.

Council members did not take part in the ceremony but will be tested because they met with Tuck for a council meeting the following day while wearing masks and social distancing. Television station WAVY first reported the mayor and council would be tested.

Tuck said he also wore a mask and observed social distancing when he participated in an in-person forum at Hampton University with Education Secretary Betsy DeVos on Friday morning, before he learned about the Northams’ test results.

DeVos’s office did not respond to a message inquiring whether she would get tested.

News of the Northams’ diagnoses came just hours before President Trump bucked the governor’s coronavirus restrictions with a large rally in Newport News. State and local health officials have said the event, which drew thousands to a hangar at Newport News/Williamsburg International Airport, could pose a “severe public health threat.” A crowd that large violates the 250-person limit Northam has imposed on public and private gatherings.

Trump’s campaign has not responded to requests for comment. But state GOP Chairman Rich Anderson has said the limit should not be a concern because Northam “has permitted huge, gargantuan numbers of people in the streets,” referring to the demonstrations that erupted in Richmond and elsewhere in the state after the death of George Floyd in police custody in Minneapolis in May. Public health officials have said there is little evidence so far that protests nationwide have led to spikes in coronavirus cases.