JOHANNESBURG -- South Africa says it has a backlog of nearly 100,000 unprocessed tests for the coronavirus, a striking example of the painful shortage of testing kits and reagents across Africa as cases steadily rise.

"This challenge is caused by the limited availability of test kits globally," the health ministry said in a statement overnight, putting the backlog at 96,480 as of Monday. Priority is given to processing tests from patients admitted to hospitals and health workers, it said.

South Africa has conducted more tests for the virus than any other country in Africa -- more than 655,000 -- and has the most confirmed cases with 27,403.

One of the latest to die of COVID-19 in South Africa was a National Health Laboratory Services employee. "We understand this tragedy will certainly test you," the ministry said in a message to her colleagues, adding that the government is committed to providing proper protective gear.

That, too, faces shortages across Africa. More than 3,400 health workers on the continent had been infected as of a week ago, according to the World Health Organization.

The shortages, especially in testing materials, have jolted African authorities into facing uncomfortable truths: Richer countries are elbowing them out in the race to obtain crucial supplies, and the continent relies almost entirely on imports for drugs and other medical items.

"We have to have Made in Africa products," the director of the Africa Centers for Disease Control and Prevention, John Nkengasong, told reporters Thursday. "We cannot keep importing basic things."

He and others, including the WHO's Ethiopian director-general, have raised the cry for fair access, including for any vaccine or treatment that emerges.

"Dozens of countries have imposed export controls on medical supplies and equipment," scores of South African and other health and activist groups said in an open letter to Group of 20 leaders last month.

Complicating matters are global powers like the United States and China promoting aid to African countries during the pandemic as part of efforts to win support on the continent. But that aid doesn't always show up.

President Donald Trump on May 21 said "we just sent 1,000" ventilators to Nigeria, but the country's information minister, Lai Mohammed, told reporters Thursday that "to the best of my knowledge they have not arrived. When they do arrive, it will be made public."

But the testing shortages are especially frustrating for African health officials, who have been praised for swiftly expanding testing capability for the virus continent-wide, from just two countries in February.

"Low levels of testing might be artificially lowering apparent infection rates," The Lancet said in a new editorial noting Africa's quick response but also the challenges that lie ahead.

Across Africa slightly under 2 million tests for the virus have been conducted, Nkengasong said, far below the target of testing 13 million people -- or 1% of the continent's population of 1.3 billion.

In Nigeria, Africa's most populous country with some 200 million people, just under 50,000 tests for the virus have been conducted, according to the country's Center for Disease Control. Nearly 9,000 cases have been confirmed while worries grow about undetected spread of the virus in the north.

In Ethiopia, Africa's second most populous country with some 110 million people, the health ministry says more than 96,000 tests have been conducted. More than 830 cases have been confirmed.

As of mid-May, Chad had carried out 105 tests per million people and Mali had tested just 173 per million, compared to some 38,000 tests per million in the United States, the International Rescue Committee said last week.

By the end of this week 2.5 million tests will have been distributed to Africa's 54 countries, the Africa CDC's Nkengasong said.

Despite the shortages, "I'm optimistic that in the next two to three weeks it will be very different," he said, without giving details.

So far African nations have relied on tests donated by the Jack Ma Foundation, sourced via partners including the WHO and procured via a newly created platform that pools African countries' purchasing efforts on the international market.

Meanwhile, efforts at domestic production of testing materials have begun in South Africa, Morocco, Senegal and Kenya, the Africa CDC has said, with plans to have those countries aid each other in evaluating the products.

"Africa is a continent that needs its own internal capacity to produce diagnostic kits," South African Health Minister Zweli Mkhize told reporters on Thursday. "We need several millions of these kits."

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Sam Olukoya in Lagos, Nigeria and Krista Larson in Dakar, Senegal contributed