More African countries closed their borders Thursday as the coronavirus’ local spread threatened to turn the continent of 1.3 billion people into an alarming new front for the pandemic. Africa is seeing an “extremely rapid evolution,” the World Health Organization’s regional chief, Dr. Matshidiso Moeti, told reporters. Thirty-six of Africa’s 54 countries now have cases, with the total over 720. Chad and Niger announced their first cases Thursday. The first case in sub-Saharan Africa was announced Feb. 28, less than three weeks ago. Moeti said she did not believe that large numbers of infected people are going undetected but acknowledged a shortage of testing kits. Forty-three countries have testing capability, up from two when the outbreak began. By Monday, countries will have 60,000 testing kits. The WHO regional chief also expressed concern about travel restrictions and their impact on the ability to deliver needed resources. The WHO is considering humanitarian corridors, Moeti said. But many African nations were taking their cue from China and other countries by sharply restricting travel.