The chief executive of America's largest rural nonprofit health organization says he tested positive but will refuse to wear a mask when he returns to work.

South Dakota's Sanford Health president and chief executive officer Kelby Krabbenhoft told staff in an email he had experienced COVID but had returned for duty and won't wear a mask.

"For me to wear a mask defies the effectiveness and purpose of a mask and sends an untruthful message that I'm susceptible to infection or could transmit it," Forbes quoted him as saying. "I have no interest in using masks as a symbolic gesture."

In the email, he said he "contracted the virus, felt the uncertainty that accompanied the word 'positive.' " He added he experienced the lagging "coughs and fatigue" but he was "back in my office," CNN reported.

Currently, the Centers for Disease Control recommends wearing a face covering - even if a person has already been infected with the virus - which has now sickened more than 12 million Americans. It is not clear if a bout of the disease confers immunity on a patient, the Centers for Disease Control and Prevention said.

"It's appalling to read this from a hospital chief executive," a Sanford Health nurse, who asked not to be named for fear of being fired, told CNN. "We're supposed to be leaders in the community. How can we be taken seriously when this is our CEO?" she said.

South Dakota is in the middle of a rising coronavirus outbreak as the U.S. braces for a challenging winter of fighting the virus ahead of the hoped-for immunizations expected to be available by mid-December. South Dakota Gov. Kristi Noem has not enforced a government directive to compel the wearing of masks.

Sanford Health, which has 1,400 doctors and includes 46 hospitals, is based in Sioux Falls, South Dakota - where the state's City Council voted this week to approve a mask ordinance.