Africa's leading public health official will write to the US Secretary of State on Thursday to highlight how the US aid freeze is threatening the lives of people across the continent and efforts to contain disease outbreaks that could ultimately impact Americans.

Jean Kaseya, head of the Africa Centres for Disease Control and Prevention (CDC), will raise concerns with Marco Rubio about the impact on patients with diseases like HIV and the risk of an mpox pandemic also fuelled by conflict in eastern Congo, he told Reuters.

"When I got the information about the pause ...I was alarmed," Kaseya said. "How can we respond to all of the ongoing outbreaks if we don't have funding?”

Kaseya wrote to African leaders over the weekend warning that without urgent intervention to plug the financial gaps caused by the US freeze and other governments cutting aid budgets there could be an additional 2-4 million deaths from preventable diseases a year on the continent.

"This pause will not just affect Africa but also the US," he said, warning that disease outbreaks will spread further without fully-funded efforts to stop them.

Conflict was also threatening the health response in parts of Africa, Kaseya added, which he included in both letters.

Fighting in the eastern Democratic Republic of Congo has impacted the mpox response as well as measles and cholera outbreaks, he said. For example, millions of doses of mpox vaccines, including doses donated by Japan for children, are stuck in Kinshasa because of the security situation in Goma.

"The US and others don't have to forget the lessons of COVID. When you don't open your eyes to something ongoing in Africa, we can have a mutation of the virus that will become a pandemic and affect all of us," said Kaseya.

The US aid pause and funding freeze means Africa CDC is short around $200-million for its efforts to fight mpox, he said, part of the $1.1-billion originally pledged.

For this and other efforts the aid freeze must be lifted quickly, he said, although he thanked Rubio for the waiver put in place for lifesaving aid and the President's Emergency Plan for AIDS Relief (PEPFAR).