Microsoft co-founder Bill Gates has invested billions of dollars into tackling malaria. It has paid off. Deaths from the disease fell by more than 60 percent between 2000 and 2015, meaning 7 million lives were saved.
In 2016, however, that trend was reversed. There were more than 216 million reported cases in 91 countries — an increase of 5 million from the previous year.
On the sidelines of this week's London Commonwealth Heads of Government Meeting, Gates told delegates, including several African leaders, the fight against malaria must be stepped up.
"If we do not keep innovating, we will go backwards," he said. "If we do not maintain the commitments that we are making here today, malaria would go back up and kill over a million children a year, because the drugs and the insecticides are evaded by the mosquito and the parasite."
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Malaria is estimated to cost the African economy more than $12 billion per year and consumes up to 40 percent of national health care budgets on the continent. Children and pregnant women are most severely affected.
The increase in cases is caused by a number of factors, professor Alister Craig of the Liverpool School of Tropical Medicine said via Skype.
"We are seeing quite dramatic increases in the resistance to the insecticides that we use to control the insect vector populations, and that has been really the mainstay of the gains, and very remarkable gains, that we have seen over the last few years," he said. "And we are just beginning to see that the parasites are starting to develop resistance to the drugs that we use to treat them."
Craig added that the fight against malaria would most likely become harder.
"We have gained what might be called the easier gains, and now we have got the harder ones to do," he said. "And they take even greater implementation and newer tools to allow us to look at where transmission is taking place."
Such new tools cost money, but funding has plateaued. At the Commonwealth conference, Britain pledged more than $2 billion to fight the disease, while Gates put forward another $1 billion and urged the international community to do more.
An earlier version of this story mistakenly identified the Liverpool School of Tropical Medicine as being affiliated with the University of Liverpool. It is not. VOA regrets the error.