Members of Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE's staff had pneumonia before the candidate came down with it, according to a report.

At least half a dozen senior staff members in Clinton's Brooklyn headquarters battled the illness before the Democratic presidential nominee was diagnosed with the illness on Sunday, People reported Monday.

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“Everyone’s been sick,” a campaign source told the publication.

The source said pneumonia cases began popping up among Clinton's staff in late August, two weeks before the former first lady’s diagnosis. Among those affected were campaign aides who travel closely with Clinton.

Campaign manager Robby Mook was among those who were sick. Two of Clinton’s top advisers received emergency medical treatment during their illness.

One top adviser was receiving antibiotics for a respiratory infection days before Clinton’s own diagnosis for pneumonia.

Another staffer was taken by ambulance to the emergency room, People’s source added, after collapsing from what was discovered to be severe dehydration.

Videos emerged Sunday showing Clinton stumbling as she was helped into a black van during a 9/11 memorial ceremony.

Clinton’s doctor said later that evening that the former secretary of State had been diagnosed with pneumonia last Friday.

Dr. Lisa R. Bardack added Clinton is “re-hydrated and recovering nicely” after feeling overheated due to dehydration before the incident.

“She is fine now,” a source who was with Clinton on Sunday told People. "She had been standing for a while in the heat."

“After she cooled off at Chelsea’s, she made a point to take a walk outside Chelsea’s apartment building to prove she was OK,” the source added.

Donald Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE, the GOP’s presidential nominee, has repeatedly suggested Clinton lacks the physical health and stamina for the presidency.

Trump on Monday said “something’s going on” with Clinton’s health, adding he hopes for her quick recovery.

Clinton’s campaign said late Sunday it would cancel her trip to California starting Monday for fundraisers and an appearance on the talk show “Ellen."