(Reuters) - Amazon.com Inc AMZN.O is at the front line of responding to outbreaks of the novel coronavirus in the United States, delivering essential goods while more than half the population faces government stay-at-home orders.

FILE PHOTO: A 3D printed Amazon postal package is placed on a keyboard in front of a displayed stock graph and the word for the coronavirus disease, COVID-19, in this illustration taken March 25, 2020. REUTERS/Dado Ruvic/Illustration

However, news reports that a handful out of Amazon’s hundreds of thousands of U.S. warehouse workers have contracted the virus raise the potential of future site closures and operational disruptions at the world’s largest online retailer.

The COVID-19 cases have led to unrest among some staff. Fifteen workers at a more than 5,000-person Amazon warehouse in Staten Island, New York, walked off the job on Monday, leading the company to fire one of them who was violating a paid quarantine.

Employees have also protested in other countries, including dozens of Amazon workers at a facility near Florence, Italy this week.

The following is a list of 19 company warehouses across the United States where one or more instances of COVID-19 have been reported. Amazon said in a statement it has taken preventive action and that workers’ health and safety is its top priority.

According to logistics consultancy MWPVL International Inc, Amazon has 519 facilities in its U.S. distribution infrastructure — including fulfillment centers, delivery stations and warehouses.

QUEENS, NEW YORK - On March 19, Amazon said it was temporarily closing delivery station DBK1 after an associate there tested positive for the virus. It was the first known case at an Amazon warehouse in the United States.

SHEPHERDSVILLE, KENTUCKY - Amazon said it shut a warehouse until April 1 at the direction of the state’s governor. Several workers at the site, known as SDF9, had contracted COVID-19. The facility handles apparel and footwear, according to MWPVL.

OKLAHOMA CITY, OKLAHOMA - A worker at Amazon's OKC1 fulfillment center said until he had tested positive, he needed to keep working to pay his bills. "I hope I didn't spread it," he told local television station News 4. here

BROWNSTOWN, ROMULUS and SHELBY CHARTER TOWNSHIP, MICHIGAN - Three facilities near Detroit have had cases of the virus, including an Amazon sorting center here and two Amazon here fulfillment centers here, the company said in local media reports.

WALLINGFORD, CONNECTICUT - Amazon told local broadcaster WTNH last week here that it was supporting a now-quarantined individual at its facility here who had the coronavirus. The site has stayed open, the report said.

LUZERNE COUNTY, PENNSYLVANIA: The company told Reuters that an employee at the facility had tested positive for the coronavirus.

JOILET, ILLINOIS - A worker, who was last at a fulfillment center in this city southwest of Chicago on March 18 and now is in quarantine, caught the virus, Amazon told the Herald-News here.

KATY AND HOUSTON, TEXAS - Amazon told local news that a management team member at a delivery station in the Katy area and another employee in the Ella, Houston area had tested positive for the disease.

JACKSONVILLE, FLORIDA - A fulfillment center employee tested positive for the virus, Amazon told local news here, which quoted an anonymous worker as saying the person was "upset, angry, scared — basically in fear for my safety, in my own immediate (family's) safety".

CALEDONIA, MICHIGAN: The company told Reuters that an employee at the facility had tested positive for the coronavirus.

MORENO VALLEY, CALIFORNIA - Amazon notified employees at its ONT8 fulfillment center that a worker had contracted COVID-19. Last at the facility on March 18, the person has since received medical care and has gone into quarantine, the Desert Sun reported. here The warehouse is continuing operations, the report said.

STATEN ISLAND, NEW YORK - CNN has reported here that a worker at a fulfillment center in New York City's least-populated borough had the virus.

EDISON, NEW JERSEY - Local news reported here that an employee at the facility southwest of New York had tested positive for the virus.

INDIANAPOLIS, INDIANA - The company told Reuters that an employee at the facility had tested positive for the coronavirus.

KENT, WASHINGTON - Amazon told Reuters that at least one worker at the facility had tested positive for coronavirus.

EASTVALE, CALIFORNIA - The company said that at least one employee at the facility tested positive for the virus.