SAN JOSE (CBS SF) — The number of people infected by a deadly COVID outbreak at a Kaiser hospital emergency room in San Jose linked to a staffer wearing an inflatable costume on Christmas has grown.

Kaiser Permanente said in a statement on Tuesday that 60 staff members at the Kaiser San Jose Medical Center who were present on December 25 have tested positive for COVID-19. The healthcare provider said physicians have also contacted 70 patients who were treated and discharged from the emergency department that day and that testing is being made available to them.

Earlier in the day, the Santa Clara County Public Health Department said they had confirmed 51 cases. “This is a stark reminder that COVID-19 can be so easily transmitted through the air and that even letting your guard down for a moment can have consequences,” health officials said in a statement.

The health department said Kaiser is responsible for complying with all applicable public health orders and work safety regulations, including those with Cal/OSHA, including timely reporting of cases and all required follow-up.

One emergency room employee has died because of COVID-19 complications following the outbreak, which was originally reported on Saturday. Kaiser officials have blamed a staffer wearing an inflatable Christmas tree costume on December 25th for triggering the outbreak.

“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,” the hospital said in a statement.

The hospital’s emergency department has undergone deep cleaning and the hospital remains open.

A hospital official said Monday additional staff members have been given a heads up in recent days about working in the event there is a staff shortage at the San Jose hospital following the coronavirus outbreak.