Cunningham, 35, was accounted for missing February 16 by his folks, who set out from Maryland to keep an eye on their child after he phoned in debilitated to work at the Centers for Disease Control and Prevention four days sooner, The Atlanta Journal-Constitution already revealed.
The younger Cunningham left work early February 12, reportedly feeling ill.
Anyone with information on this case is asked to call 911.
The Harvard-educated epidemiologist was promoted in July at the US Public Health Service in Atlanta and contributed to responses to outbreaks of Zika, Ebola and health emergencies caused by Hurricane Sandy.
A $10,000 reward has been offered for anyone with information.
Terrell Cunningham also had concerns about recent interactions with his son, whom he described as focused on a host of professional and personal issues. They say there is no evidence of foul play.
"The most unusual factor in this case is that every single belonging that we are aware of was located in the residence so his keys, cell phone, debit cards, credit card, wallet", said O'Connor.
The missing man's father, Terrell Cunningham, told WSB-TV that his son graduated from Morehouse and got a master's degree and doctorate from Harvard University. The CDC called Cunningham "a highly respected member of our CDC family", in a statement sent to ABC News.
At the CDC, Cunningham is a team leader and has researched health differences related to race, ethnicity, socioeconomic status, gender, and geography. "Not having his phone, leaving his dog Bo alone, he just wouldn't voluntarily check out like that", his brother, Anterio Cunningham, told Fox5 on Monday.
Cunningham works in epidemiology, trying to understand health differences across demographics. "He would not be the type of person that, you know, if you kidnapped him and held him, he could give you access to some horrific virus that could be a real problem for the rest of us", O'Connor said. The mother said she saw the message later as her phone was on silent mode.
When they arrived at their son's house after he went missing, the parents said, they felt something was wrong because he had left his Tibetan spaniel unattended. Police believe that Cunningham made it to his northwest Atlanta home, but from there the trail goes cold.