Hillary Clinton’s pneumonia, which caused her to collapse on the way out of a 9/11 memorial ceremony Sunday morning, has reportedly spread to her campaign staff.

"A debilitating bug" hit Clinton’s staff at her campaign headquarters and aides traveling with the Democratic nominee two weeks before she was diagnosed with pneumonia, a campaign source told People.

No one on the campaign staff seemed to be spared from the bug, People reported Monday.

At least half a dozen senior staff were felled, including campaign manager Robby Mook. Two top advisers even needed emergency medical treatment, the source says. One top adviser diagnosed at a Brooklyn urgent-care center with a respiratory infection was being treated with antibiotics in the days before Clinton’s diagnosis. Another top adviser was taken by ambulance to the ER by ambulance after collapsing from what turned out to be severe dehydration, the source said.

Others noted that Clinton staffers came down with the sickness.

senior Clinton staff also came down w/ pneumonia or, what was described as, an "ugly bug" I’m told. — Sam Stein (@samsteinhp) September 12, 2016

Clinton collapsed Sunday morning after leaving a 9/11 remembrance ceremony at the World Trade Center site. The campaign initially said that she had overheated but later in the day said she had been diagnosed with pneumonia on Friday.