WASHINGTON – The Secret Service’s Uniformed Division has sustained a coronavirus outbreak, according to four people briefed on the matter, the latest blow to a beleaguered agency that has faced challenges in performing its duties during the pandemic.

The outbreak is at least the fourth to strike the agency since the pandemic began, further hobbling its staffing as it continues to provide full protection to President Donald Trump and prepares for the number of people it is charged with protecting to grow because of the election of Joe Biden.

At least 30 uniformed Secret Service officers have tested positive for the virus in recent weeks, and the agency asked about another 60 to quarantine, according to the people, who spoke on the condition of anonymity because they did not want to be identified discussing personnel matters. At least a handful of agents also tested positive or were forced to isolate, two of the people said.

The Washington Post first reported the outbreak.

It was unclear how the officers contracted the virus. Many traveled to Trump or Biden campaign events in the final weeks of the election, the people said. Several senior White House officials and Trump allies also contracted the virus after attending an election night party at the White House.

A spokeswoman said the Secret Service kept up its duties during the campaign season and that it was taking precautions, including testing, contact tracing and isolating people as needed, to respond to COVID-19.

“The health and safety of our workforce is paramount,” said the spokeswoman, Julia McMurray.

Officers in the Uniformed Division have different responsibilities from the famed Secret Service agents who guard presidents and their families. The officers provide protection for physical locations like the White House and the vice president’s home at the Naval Observatory in Washington. They also screen crowds at public events. The division — which has 1,600 officers — was widely faulted after fence jumpers breached the White House grounds during former President Barack Obama’s second term.

Many officers and agents privately expressed concerns in the final weeks of the presidential race about traveling to campaign events across the country. They feared contracting the virus at the events or while traveling, according to two people briefed on the matter.

The pandemic has been particularly taxing on law enforcement agencies whose officers come in direct contact with people to do their work. In the first few months of the outbreak, one in six New York Police Department officers were out sick or on quarantine.

The pandemic has created unique problems for the Secret Service as the nature of its work — especially during a presidential campaign — forces the agency to deploy its agents across the country, including to events held by Trump where social distancing was rarely practiced and wearing masks was not required.

In the most glaring example of the dangers agents faced, Trump held a rally in June at an indoor arena in Tulsa, Oklahoma. One of Trump’s allies who attended the event, Herman Cain, died from the virus six weeks after the rally.

In August, at least 11 employees at the Secret Service’s training facility in Maryland tested positive for the virus. The agency had shuttered the facility earlier in the year to develop procedures to mitigate transmission of the coronavirus. But several trainees were believed to have contracted the virus during training exercises and at a nearby hotel where they practiced no social distancing.

Earlier in the summer, two members of the Secret Service who were dispatched to provide security at the Tulsa rally tested positive. Around that time, Vice President Mike Pence canceled a trip to Florida after members of his detail showed symptoms of the virus.

The latest outbreak comes at a time when the Secret Service’s resources are already stretched. During a transition, the agency is expected to provide more protection for the president-elect and vice president-elect and their families while continuing its regular duties of protecting the president and his family.

During his hospitalization for the coronavirus in October, Trump had an agent drive him past a group of supporters outside the hospital. Medical experts said Trump was likely contagious at the time and that the agents who were in a hermetically sealed Chevy Suburban with him could have easily been infected, even though they were covered in the same kind of personal protective equipment used by medical professionals.