SAN JOSE — About the only sign of holiday cheer on Christmas morning in the emergency department at Kaiser Permanente San Jose was a string of garland tacked up at the doctors’ station.

So when a staff member came bounding down the hall the morning of Dec. 25 dressed in an inflatable Christmas tree costume, the moment of levity was a welcome respite.

“She was just spreading joy,” said a nurse who worked that morning.

Instead, her battery-operated, air-powered costume may have spread the coronavirus throughout the ER. In the days since, 44 staff members have become infected, and on Sunday night Kaiser announced that one of the employees working Christmas Day has died, a tragedy that is making worldwide headlines. It wasn’t clear Monday whether any visitors or patients to the unit were also infected.

Many of the sickened staff members had already received the first of two doses of the COVID vaccination in the previous week, Kaiser said, but its partial effectiveness — which usually starts in about 10 days — hadn’t kicked in. The woman in the costume had no symptoms at the time but subsequently tested positive.

In an interview Monday, the nurse  — who didn’t want to be named because she feared for her job — gave one of the first inside accounts of how the deadly virus might have spread. She explained that sometime between 9 a.m. and 10 a.m., the woman in the costume spontaneously appeared at the central nurses station. The nurse was wearing a mask and a face shield when she briefly interacted with the costumed woman from about six feet away, she said.

Two days later, on Dec. 27, the nurse fell ill and has been sick with mild COVID-19 symptoms ever since. Most of her coworkers began feeling ill around the same time, she said, and while she is aware of coworkers who have severe symptoms, she doesn’t believe any are hospitalized.

How could a tree suit with a red nose and silly smile become a lethal superspreader? A battery-operated fan helps inflate the tree and may have spewed viral droplets farther than the normal person-to-person spread.

The nurse emphasized there was no party or gathering around the woman in the costume and that her arrival in the tree suit was “spur of the moment” and unplanned. Everyone in the emergency department wears masks, the nurse said, and “we don’t hug.”

Early reports erroneously suggesting a party atmosphere in the emergency department “painted us in a light of being irresponsible when we’ve been working our butts off to save lives. We’re not seeing our families. It portrayed us as not caring about our community.”

A medical worker walks in front of the emergency entrance at the Kaiser Permanente San Jose Medical Center in San Jose, Calif., on Monday, Jan. 4, 2020. (Dai Sugano/Bay Area News Group) 

The annual Christmas party had long been canceled, and unlike in years past, no one wore Santa hats or candy cane headbands in the ER — they’re too easy to get tangled up in face shields and protective respirators.

The jaunty Christmas tree was “so innocent,” the nurse said.

As she described it, “you just see this Christmas tree coming bounding down towards you, and it makes you smile. It was a brief moment of levity, and you get back to working.”

The death of a staff member — reportedly a registration clerk — was a crushing blow to the hospital staff that is already exhausted after treating COVID patients for 10 months and remains “a heavy burden” for the woman in the costume.

The tragedy is like “a death in the family,” the nurse said.

“We’re physically exhausted and emotionally already taxed, and this is just more on top of it,” she said. “People don’t realize the toll that it takes and just what it takes for us to come in and do what we do. Yes, we’ve chosen this profession and we’re all very good at our jobs, but that doesn’t make it any less stressful or any less emotional or less devastating when you lose a family member.”

The Santa Clara County Health Department is investigating the outbreak.

“Obviously, this is a highly unusual situation involving a well-intentioned staff member acting on their own without advance notice or approval,” according to a statement from Irene Chavez, senior vice president and area manager, Kaiser Permanente San Jose Medical Center.

The hospital is conducting contact tracing to notify and test any staff or patients who were exposed and is adding weekly testing for staff.

The hospital did not answer Monday whether the woman in the costume worked a shift that day. It said it was investigating whether the virus spread beyond those who worked that morning. It also didn’t explain its coronavirus testing policy, which the nurse said was a sore spot for a number of nurses who complained that the hospital started more rigorous testing of staff only after the outbreak.

Monica Gandhi, an infectious-disease expert at UC San Francisco, said the outbreak appeared to be a combination of “so many unlucky things,” including the unusual air-blowing costume and the timing of the vaccine doses.

Although there’s some slight variation depending on whether the vaccine is from Pfizer or Moderna, each generally takes about two weeks to be roughly 80-90% effective. Within the first 10-14 days, it’s closer to 50% effective, she said.

“That’s why some of these health care workers have gotten one dose and still gotten COVID,” Gandhi said.

SAN JOSE, CA – JANUARY 04: The Kaiser Permanente San Jose Medical Center along Hospital Parkway is seen in San Jose, Calif., on Monday, Jan. 4, 2020. (Dai Sugano/Bay Area News Group) 

The Kaiser nurse said she is still baffled that this costume with the battery-operated fan could have wreaked this much havoc and doesn’t understand how people who worked later in the day also got sick.

“It just doesn’t seem completely plausible that it was all her because it was just a moment in time compared to what we deal with all the time,” the nurse said. “How could it be that if this occurred at 9 in the morning that people were being infected at three o’clock in the afternoon? Could this happen? Yes. But was it tragically coincidental or something else? We just don’t know.”

Staff Writers Emily DeRuy and Evan Webeck contributed to this report.