A public health investigation found that at least 31 employees across four Costco locations in Santa Clara County have tested positive for COVID-19, revealing a cluster of infections that may have occurred in retail stores during the month of July, according to a statement by the county Thursday.
County officials confirmed the most cases, 13, were at the Sunnyvale Costco, followed by eight at the Senter Road location in San Jose. Six cases were reported at the Gilroy Costco, and four were discovered at the Mountain View location.
While the investigation is ongoing, early results indicate that the employees contracted the virus by way of "community transmission," rather than infection between employees. In a press conference Thursday, Marty Fenstersheib, the county's COVID-19 testing officer, said it's likely that the infected employees had contracted the virus during "day to day" activities, as opposed to getting it inside Costco or from other employees.
Costco representatives did not immediately respond to a request for comment.
Public health officials are conducting contact tracing to see who else may have been infected with COVID-19, and are reviewing the safety and social distancing policies at each store location to see if they comply with county health requirements. The Mountain View location had yet to be inspected as of Thursday, but the other three locations showed that Costco had largely adhered to the public health rules, Fenstersheib said.
No store locations have been shut down so far, Fenstersheib said, and public health officials are not dissuading customers from going to Costco.
"We feel that the public is totally safe in continuing to shop at Costco, but we still remind everyone to wear your mask and keep your social distance in any retail stores, including Costco," he said.
In the case of the San Jose Costco, public health investigators opted to test all of the employees to see who else may have been infected, but it's not clear whether the same will be done for the remaining Costco sites with case clusters. Fenstersheib said it's not unusual to have that many employees test positive when each location has something like 300 or 400 employees, but that any workplace with three or more cases prompts immediate action from the county.
Investigations into workplace clusters are a key part of the county's public health response to the coronavirus pandemic, particularly businesses and activities that include public contact. Employers are required to follow a step-by-step protocol when an employee tests positive for COVID-19, including reporting it to the county.
A similar string of COVID-19 outbreaks was reported last month at construction sites across the county, with the largest outbreak in Mountain View. Ten people tested positive for COVID-19 and 30 more were potentially exposed to the virus.
As of Thursday, public health investigators have found that the customer areas of the affected Costco locations have fully met the county's health standards. Some changes have been recommended to the employee areas, Fenstersheib said.