The US plan to withdraw from the World Health Organization (WHO) will squeeze Africa's health initiatives, the Africa Centres for Disease Control and Prevention said on Thursday, calling on African countries to find alternative sources of financing.

US President Donald Trump signed an executive order on the WHO exit on Monday, shortly after his inauguration to a second term.

The concerns raised by Africa's leading public health officials are a sign of the potential impact of the US decision on the UN agency's ability to fight diseases and respond to emergencies round the globe without its biggest funder.

Africa CDC senior official Ngashi Ngongo said many countries had been relying on US investment via the WHO to fund public health drives.

"We know the role that the WHO has played on the continent... to really improve the delivery of health programmes," Ngongo told a media briefing.

"The reduction or the cutting of (US) funding is definitely going to affect the response.

"It is time for some of the African member states to rethink the financing of public health."

Zimbabwe's finance minister on Wednesday expressed concern that the US withdrawal could signal cuts in health aid to countries such as his that are most affected by HIV/AIDS.

Ngongo said once Africa CDC takes stock of the situation, it might explore funding opportunities with other non-African countries to compensate for the expected fall in WHO support.

While Ngongo does not expect Trump's order to have a big impact on Africa CDC, he expressed concern a joint action plan the health body had been developing with the US government over the past year could also now be at risk.