*Former Secretary of State Colin Powell and NBA star Shaquille O’Neal have joined a Twitter campaign that encourages followers to help end malaria by donating money to buy bednets, which guard against the mosquitoes that spread the disease in Africa.

Billionaire Bill Gates, Queen Rania of Jordan, Ashton Kutcher, Ryan Seacrest and other stars have also joined the Twitter drive, which begins today with guidance from the United Nations Special Envoy for Malaria, Ray Chambers.

“It’s one of the few campaigns I’m aware of where $10 buys a bednet which can save a child’s life,” Chambers told Reuters. “The tangible feel of it is greater than any other campaign I’ve been exposed to.”

Gates will also take part in tonight’s live “Idol Gives Back” fundraiser to promote the fight against malaria and other health causes.

Malaria causes more than 1 million deaths annually worldwide, but the problem is most acute in Africa. The UN aims to reduce the deaths from malaria to near zero in Africa by 2015. So far, more than $4 billion has been raised to fight the disease, mostly from the World Bank, government agencies and the Bill and Melinda Gates Foundation.

Others taking part in the Twitter campaign include talk show host Larry King, singer Jordin Sparks and Sarah Brown, the wife of British Prime Minister Gordon Brown, organizers said. Collectively, the participants have 50 million Twitter followers.