By Marissa Parra

CHICAGO (CBS) — Another essential worker is among the number of fatalities due to COVID-19, and she is the first active letter carrier in Chicago to die from the virus.

Unique Clay was a letter carrier with the United States Postal Service, and she had just given birth. It is not clear how she got the virus.

“The family is picking out caskets, and her birthday is one month from today,” said Unique’s father, Alan Brown.

Clay was a Chicago letter carrier for two years, but the job she loved most was being a mom. She just gave birth to her third last Thursday. She died the following Tuesday.

“When she went in labor, she told me, ‘Mom, I feel like I’m coming down with a cold,'” said Unique’s mother, Annette Clay.

Her family says Unique was tested for COVID-19 from the delivery room at the University of Chicago Medical Center. Her results came back positive.

They say she was later discharged with her newborn. Days later, she told her oldest daughter to get her inhaler, because she couldn’t breathe. When the 11-year-old came back her, mother was dead.

“My newborn niece, she will never get to know her mom,” said Unique’s sister Dajah Brown.

It’s unclear exactly how she got the virus, but her death marks the first COVID-19 loss among Chicago letter carriers.

The letter carriers unions says they are just like the rest of the essential workers who have taken no breaks during the pandemic.

“Our members have to take extra precaution out there,” said union president Mack Julion. “The American people are counting on us to deliver.”

Saturday standing six feet apart, with masks on their faces and balloons in hand, they said their goodbyes, some of them using their lunch breaks to honor their fallen colleague before having to get back to their routes.

“We want letter carriers to be tested,” Julion said. “We are essential. We’re out there. We’re engaging with the public daily. So they can get home safely to their families.”

The union says it has been tracking these cases. Close to 40 letter carriers in Chicago have tested positive for COVID-19.

The family says they want answers. They don’t understand why Unique was discharged and sent home just days after testing positive.

CBS 2 reached out to the hospital to ask if they recommended that Unique was put in quarantine and why she was discharged after testing positive. A spokesperson for the hospital said, “The University of Chicago Medicine community extends the deepest sympathy to the family. We cannot comment on individual cases due to patient privacy laws.”