Irene Chavez, senior vice president and area manager at San Jose Medical Center, said Sunday that 44 staff members in the emergency department have tested positive for the virus since Dec. 27.
By Tuesday evening, that number had risen to 51, according to reporting from San Francisco’s KRON4.
The Oakland-based hospital chain is investigating the outbreak and said the source could be a blow-up, holiday costume worn by a staffer who "briefly" visited the department Dec. 25, according to its statement.
Inflatable costumes usually rely on battery-operated fans to suck air into the costumes to keep their shape. COVID-19 spreads through droplets in the air, which is why investigators are looking into the air circulation function of the fan.
"Any exposure, if it occurred, would have been completely innocent, and quite accidental, as the individual had no COVID symptoms and only sought to lift the spirits of those around them during what is a very stressful time," Chavez said, adding that the holiday costume was not approved beforehand by Kaiser.
"Obviously, we will no longer allow air-powered costumes at our facilities. At the same time, we are taking steps to reinforce precautions among staff, including physical distancing and no gathering in breakrooms, no sharing of food or beverage and masks at all times," she said.
Hilary Costa, a Kaiser Permanente spokeswoman, said she did not know what kind of costume the person was wearing. NBC affiliate KNTV-TV in San Jose reported Sunday that the costume was a Christmas tree.
Kaiser declined to identify the employee who died of COVID-19 complications.
The emergency department is open and undergoing a deep cleaning, Chavez said. Nearly 40,000 Kaiser Permanente health care workers in Northern California have already received COVID-19 vaccinations, she said.
The Associated Press contributed to this report.