GENEVA — Health officials in Africa say the rollout of rapid diagnostic tests for COVID-19 could be a "game changer" for their fight against the coronavirus but also warned Thursday that increased testing could drive up confirmed cases on a continent that has seen them decline or plateauing as case numbers soar in the West.

Some experts worry that Africa so far has lacked the ability to test widely enough, especially in hard-to-reach rural areas, and that its case counts therefore don't reflect reality and impede tracking the virus.

"African countries are gearing up to introduce antigen-based rapid diagnostic tests on a large scale, and this will be a game changer, we think, in the fight against COVID-19," Dr. Matshidiso Moeti, the World Health Organization's regional director for Africa, said. "These high-quality rapid tests will help meet the huge unmet need for testing in Africa."

– prompting some governments to pull back from their toughest containment measures.

"As countries ease restrictions on movement, some increase in cases is expected, but preventing an exponential rise is absolutely critical," she said.

From early on in the pandemic, officials at WHO headquarters in Geneva, including the U.N. health agency's Ethiopian director-general, Tedros Adhanom Ghebreyesus, have expressed concerns that COVID-19 could have a big impact on weaker health systems like those in Africa.

However, developed countries with world-class health systems so far have been among the ones hardest hit by virus outbreaks. WHO's 54-nation European region tallied 927,000 cases in its latest weekly count, a new record high.

Dr. Susan Ndidde Nabadda, head of the Ugandan National Health Laboratory Services and Central Public Health Laboratory, suggested that it could take some time to ensure proper authorizations and a high-quality process before rapid diagnostic tests on a broader scale because "there is no longer really a lot of emergency" in Africa.

Nabadda cited reports indicating that the identification of COVID-19 cases increased in Guinea once the west African country started rolling out the RDTs, noting that "we might see more numbers coming on board" as the tests are deployed more widely.

She said the relative lack of testing in Africa could be one of the reasons why African case counts were lower than in developed countries.

WHO announced last month that it and leading partners have agreed on a plan to roll out 120 million rapid diagnostic tests for COVID-19 to help lower- and middle-income countries make up ground in a testing gap with richer countries.

The antigen-based rapid diagnostic tests for which WHO issued an emergency use listing are intended to provide better testing access to areas where it is harder to distribute the PCR tests often in many wealthier nations.

The rapid tests look for antigens, or proteins found on the surface of the virus. They are generally considered less accurate — though much faster — than PCRs, which are higher-grade genetic tests. PCR tests require processing with specialty lab equipment and chemicals. Typically, delivering results to patients takes several days.