Health officials said they are conducting an investigation into a COVID-19 outbreak among the emergency room staff at a San Jose hospital that has infected 44 people since Christmas, when a staffer wore an "air-powered" costume to cheer everyone up.

The Kaiser Permanente San Jose Emergency Department employees tested positive between Dec. 27 and Jan. 1, according to Irene Chavez, the hospital's senior vice president and area manager.

The infected employees are isolating and not coming into work, Chavez told ABC News in a statement.

MORE: California COVID-19 cases surge, straining the health care system

"We will ensure that every affected staff member receives the care and support they need," Chavez said in the statement.

Chavez added that the hospital's emergency room has undergone a deep cleaning and the medical facility is open and safe for patients.

Chavez said contact tracers are looking into an incident on Christmas where one staff member wore an air-powered inflatable suit in an activity that was not planned or approved by hospital officials.

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"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," she said. "If anything, this should serve as a very real reminder that the virus is widespread and often without symptoms, and we must all be vigilant."

Chavez said the hospital has informed the staff that those costumes and devices aren't allowed and they need to adhere to health guidelines and precautions.

What to know about the coronavirus:

• How it started and how to protect yourself: Coronavirus explained

• What to do if you have symptoms: Coronavirus symptoms

• Tracking the spread in the U.S. and worldwide: Coronavirus map

44 California emergency room staffers infected with COVID-19 after Christmas originally appeared on abcnews.go.com