The continent-wide everyday average was 10,300 recently, below 11,000 the week previously.
Africa had recorded 1 147 369 cases as of Thursday morning, about half of which were in South Africa, which has the fifth-highest total globally.
Noting a "sign of hope" in terms of decrease in the number of new Covid-19 cases in Africa during the past week, Nkengasong, however, emphasized the need to avoid "prevention fatigue", and further intensify precautionary measures, such as the use of masks, social distancing as well as increase testing.
Robert Redfield, the director of the Centers for Disease Control and Prevention, said this week that he's "hopeful" the coronavirus pandemic will be "behind us" by next spring.
That warning gained renewed momentum in the past few weeks as COVID-19 numbers exponentially increased across Africa.
"It's very, very early, we're dealing with a very delicate virus that spreads very quickly but it's important to recognise those slight tendencies that are positive".
But the trend must be noted with a lot of caution.
He said the continent has also seen other good news over the past week: A rise in the rate of recoveries from 72% to 76%.
But lower testing rates in much of the continent means we are still not getting the true picture of the pandemic.
The 20 million tests would be done as part of a campaign the African Union just launched: Africa against COVID-19 - Saving Lives, Economies and Livelihoods.
The Africa CDC announced last week that it would start large-scale antibody testing and that seven countries would participate in the first phase: Liberia, Sierra Leone, Zambia, Zimbabwe, Cameroon, Nigeria and Morocco.
That most cases are asymptomatic is another argument they have raised to make the point that no government in the world can claim its numbers adequately reflect the evolution of the virus.
Even with limited data, African health officials are increasingly sure that most coronavirus cases are asymptomatic - Nkengasong put the portion at 70 to 80 percent - and that deaths are relatively low, Nkengasong said.
He added, "As we then - and I do anticipate it will happen - begin to deploy an efficacious and safe COVID vaccine, then hopefully when you and I talk next spring we'll have this pandemic behind us".