A worker at the Amazon facility in Eastvale tested positive for coronavirus.
Amazon said all associates who had close contact with that person will be asked to self quarantine for 14 days.
An employee at the Costco in Marina del Rey also tested positive.
Meanwhile, grocery store workers are among those on the frontlines of the crisis as one of the essential businesses under California's stay-at-home order, but local residents weren't surprised to learn that some turned out to be infected.
"I guess figuring the number of people that are going in and out of the grocery store and the number of people who work there, I'm not super surprised," said Stephane MacDonald of West L.A.
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Vallarta Supermarket in Canoga Park closed its doors for an unknown duration after one of its employees tested positive on Friday.
The individual was last in the store on March 22, according to a statement from the grocery store chain. All employees who had close contact with the infected person were notified and are now self-quarantining for 14 days.
The supermarket said it hired a professional decontamination company to sanitize and deep clean the store before it is reopened, but an exact date was not provided.
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A Gelson's on Sunset Boulevard in Pacific Palisades temporarily closed after an employee there tested positive for the virus as well. The individual last worked at the store on March 22 and is currently recovering at home, according to statement.
Other employees who came in contact with the individual were put on a paid two-week self-quarantine.
The store was expected to reopen over the weekend after undergoing a deep cleaning and inspection.
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Meanwhile, a third person employed at a Sprouts Farmers Market on El Camino Real in Tustin also tested positive for COVID-19. The store confirmed it after rumors began circulating online.
Officials said the individual last worked at the store on March 20. All employees were notified and the store has since reopened after an extensive cleaning.
A local doctor is urging customers and workers to keep yourself and others safe by following health practices slow the spread of the potentially deadly infection.
"The way you're going to get this infection is through contact," Dr. Marc Kerner, Calwest ear, nose and throat otolaryngologist. "If you're wearing gloves or wearing a mask, you're gonna reduce your ability to contact surfaces where you can acquire the virus."
Kerner said, at the very least, grocery store workers should be wearing gloves to limit their exposure and possible spread of the highly contagious virus.
As for purchases, Kerner said there is no need to take extreme measures such as wiping down every item or leaving them outside of the home for a period of time. The best protection is to wash your hands with soap and water after coming in from shopping and again after putting away groceries, according to Kerner.
"If you can keep your hands clean, keep your face clean and you can actually protect your nose and mouth, you're gonna go a long way to not getting this virus," Kerner said.
However, he said there is no need for an N95 masks, as those should be reserved for medical personnel and first responders. A surgical or cloth mask can provide extra protection though.
"I'm using my gloves and also the mask to protect myself and also to help other people to protect from me," Glendale resident Jay Deb said.