Kemp had recently come under pressure to implement stricter measures, with several Georgia mayors surpassing Kemp to announce their own shelter-in-place orders, including in Atlanta, Savannah, and Athens.
In explaining the state's more cautious response to the pandemic, Kemp said in a press conference that he only just found out that COVID-19 could be transmitted by people before they show symptoms, or what is known as "presymptomatic."
"Those individuals could have been infecting people before they ever felt bad," he said, "but we didn't know that until the last 24 hours."
Kemp said Dr. Kathleen E. Toomey, the commissioner of the Georgia Department of Public Health, called the news a "game-changer."
The news is not, in fact, a game-changer. Officials have been warning for more than two months about the possibility of transmission by people who don’t immediately or ever show symptoms.
"You know that, in the beginning, we were not sure if there were asymptomatic infection, which would make it a much broader outbreak than what we’re seeing. Now we know for sure that there are," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said at a White House press briefing on Jan. 31.
The CDC, which is based in Georgia, has been warning since at least the beginning of March that presymptomatic spread might be possible.
"Some spread might be possible before people show symptoms," read the CDC website in early March. "There have been reports of this occurring with this new coronavirus, but this is not thought to be the main way the virus spreads."
CDC Director Dr. Robert Redfield also said on Feb. 13 that spread was possible between people who were asymptomatic, meaning they never experience symptoms.
“There’s been good communication with our colleagues to confirm asymptomatic infection, to confirm asymptomatic transmission, to be able to get a better handle on the clinical spectrum of illness in China," he told CNN. "What we don’t know though is how much of the asymptomatic cases are driving transmission."
"What I’ve learned in the last two weeks is that the spectrum of this illness is much broader than was originally presented. There’s much more asymptomatic illness," Redfield said.
Redfield did tell NPR Monday that it had since been "pretty much confirmed" that as many as 25% of people with COVID-19 remain asymptomatic.
"That's important, because now you have individuals that may not have any symptoms that can contribute to transmission," he said, "and we have learned that in fact they do contribute to transmission."
Cases of people who do not immediately show symptoms are believed to be one of the reasons the virus is spreading so widely, because carriers may not know they are infected and go about their business, infecting others.
There are currently more than 4,500 confirmed COVID-19 cases in Georgia. More than 150 people have died from the disease in the state.
Jon Ossoff, a Democrat running for US Senate in Georgia, said Kemp's "excuse for late action is a lie."
"The truth is Kemp ignored those warnings and failed to grapple with the speed and severity of this outbreak," he said. "The record must reflect these facts.”
Stephanie Lee contributed reporting.