Malaria is one of the world's biggest killers, and one of the biggest problems for Africa.
Newsround travelled to Ghana to find out about the disease.
More than 3,000 children under five are killed by malaria every day in Africa.
It doesn't always kill, but can cause extreme weakness, bad headaches and turn your eyes yellow.
It's spread by mosquitoes, and can be quite easily dealt with - if you've got the money.
Tourists can take anti-malaria pills, but these are bad for you if you take them all the time.
The best way to stop the mosquitoes biting you is by sleeping under a net, but they are often too expensive for Africans to afford.
But there is hope. Unicef - the United Nations children's fund - has set up medical centres to sell affordable nets, and show parents how to put insecticide on them.
Action like this could cut the number of malaria deaths by half, but there's still a long way to go.