Centers for Disease Control and Prevention Director Dr. Rochelle Walensky told Jim Braude on Greater Boston that there's more work to be done on coronavirus testing efforts and public messaging from the agency.

"We have more work to do. We have to make sure that tests are readily available, that people can get a test when we want them," Walensky said.

The nation's top health expert said federal PCR testing sites are still scaling up and that rapid tests will be mailed to homes soon, but she admitted that tests aren't always immediately accessible.

Public health experts have criticized the CDC, along with Walensky herself, for inadequate messaging as the coronavirus continues to spread across the nation.

"I have to acknowledge the criticism and see where and how I can do better, we as an agency can do better. But right now, my north star is making sure that the science and the information that we have lead us out of unprecedented times," Walensky said, adding that she's never had her motivations questioned when working directly with patients.

Walensky's colleague Dr. Anthony Fauci recently said he has received death threats. When asked if she has also received such threats, Walensky said: "There's been more and more attention and, you know, I'm working through it."

Watch: Dr. Rochelle Walenski on the state of COVID