by Ollie Sayeed, Ph.D.
In 1749, a young land surveyor named George Washington set out into the wetlands of Virginia, tasked with surveying the landscape of his home colony. Unlike today, the British colony of Virginia was covered with swamps that have since been drained. And unlike today, those swamps were filled with mosquitoes carrying one of the world’s deadliest killers. The 17-year-old future president’s venture into the countryside was his first experience with malaria, a disease that hundreds of millions of people today know all too well.
Malaria is caused by several closely related species of microscopic parasites carried from person to person by mosquitoes. Once injected into the bloodstream by a mosquito bite, the malaria parasite travels to the liver to multiply, creating up to a hundred trillion copies of itself that make their way back into the bloodstream and provoke the body’s immune response of fever and chills. The next mosquito searching for a meal of blood picks up some of these parasite copies when it bites, and the cycle continues with the next victim.
The resulting disease is painful for anyone unlucky enough to suffer it, even if they survive. As Washington wrote during a bout of malaria later in life: “I have in appearance been very near my last gasp…I fell into a very low and dangerous state – I once thought the grim king would certainly master my utmost efforts and that I must sink in spite of a noble struggle.” Washington would see spells of fever and shivering for the next few decades, catching the disease again at ages 30, 39, 52, and finally at 66, shortly before the end of his life.
The first president’s experience tragically represented what would follow for most of American history. In 1830, 21-year-old Abraham Lincoln caught the disease when he first moved to Illinois with his young family; five years later, he caught it again, giving him chills and fever for a month. As an older man, his memories of military service were dominated not by combat but by “a good many bloody struggles with the mosquitoes.”
When Ulysses S. Grant moved to Missouri in the 1850s, he wrote to his wife that the locals “shake with the ague all summer,” using an old name for malaria. Even the most powerful place in the country wasn’t safe. In 1881, James A. Garfield’s First Lady Lucretia caught malaria only a few weeks after moving into the White House. She was still in recovery up to her husband’s assassination two months later. The might of the US government was not enough to protect its leading citizens from the bite of a small insect.
Alongside the famous names, millions of ordinary Americans died of malaria across the 18th, 19th, and 20th centuries, making it one of the most destructive infectious diseases to afflict North America. The horrors continued up until the lifetimes of some older Americans alive today. A post-Depression surge in the 1930s reached 150,000 cases a year across the US, mainly in the South, where records from the worst-hit areas show that up to half of children were infected with the malaria parasite.
However, the tide began to turn against malaria in the middle of the 20th century thanks to government efforts towards elimination. Part of this involved changes to the landscape of the US that came along with increased wealth, like better housing conditions and the expansion of agricultural land at the expense of wetlands like those in Virginia. But it also involved policy interventions specifically guided by public health. New insecticides like DDT were sprayed on the insides of homes in areas at risk of malaria to kill off the mosquitoes carrying the disease. Bed nets covered with insecticides protected sleeping children from mosquito bites.
Altogether, the US was declared malaria-free in 1951, after just four years of the post-war federal eradication program aimed at stamping it out. The monster that tormented Washington in Virginia, Lincoln in Illinois, Grant in Missouri, and Garfield in D.C. had been vanquished.
But the global war against malaria hasn’t yet been won. The disease that public health efforts successfully banished from the United States 73 years ago still menaces tropical parts of the world today, particularly Africa, where 1,000 children under five die of malaria every day.
Mosquitoes rely on a warm climate and pools of standing water – like George Washington’s swamps – to lay their eggs. Around the globe, the areas most susceptible to malaria are those with tropical weather and high rainfall. Within Africa, malaria hotspots form a band stretching from the West African coast through the Congo rainforest into East Africa. Anti-malaria campaigns have been focused on this region of tropical Africa, targeting countries with the highest death tolls, like Nigeria, the Democratic Republic of Congo, Uganda, and Burkina Faso.
While programs to eradicate malaria continue, the geography of malaria is starting to be upended by another force: human-caused climate change. Since the 19th century, burning fossil fuels has increased global temperatures by around 2.5°F, and the planet is on course to get even hotter.
Climate change has the potential to worsen the burden of malaria through its effects on both temperature and rainfall. Because mosquitoes thrive in warm temperatures, global warming will widen the area of the globe that mosquitoes can live in and extend the length of the malaria transmission season. A warmer atmosphere can hold more moisture and lead to higher rainfall, increasing both the range of wet environments and the number of wet days in the year: both making the climate friendly to breeding mosquitoes.
The human impacts of a changing climate will also make malaria a harder problem to tackle. The storms, droughts, and floods caused by climate change can lead to displacement, forcing people out of their homes into temporary accommodations where malaria treatment is harder to access. Natural disasters and displacement, in turn, create conflict over resources that can spiral into war, turning even more people into refugees at risk of malaria.
But climate change doesn’t just pose a risk to parts of the world that already have malaria. It also increases the chances of malaria spreading in countries that had previously eradicated it, including the US. The same climatic forces warming Africa and shifting its rainfall patterns are also changing the North American climate, particularly the historical malaria hotspots in Florida and the rest of the South. Miami has a tropical monsoon climate similar to African cities like Douala, Cameroon, and Conakry, Guinea. As Africa gets hotter, wetter, and more inviting for malaria-carrying mosquitoes, so will the southeastern US.
There’s already recent evidence that malaria is starting to return to the US after nearly a lifetime away. In 2023, seven malaria cases were reported in Sarasota County, Florida, followed by two more cases in Texas and Maryland. Several of these patients had never traveled to countries with endemic malaria. In each of the three states, the disease was transmitted by mosquitoes from person to person within the US, not carried exclusively by international travelers.
Although the risk of malaria to the American public is still very low, the prospect of a future outbreak is worrying, and climate trends are pointing in the wrong direction. It would be a huge mistake to undo decades of progress towards a malaria-free US, returning to the days when a mosquito bite in Florida, Virginia, or Illinois could be a death sentence.
The only way to make the world truly safe from malaria is to eradicate the disease altogether. Thankfully, decades of experience tackling malaria have given us a wealth of tools, from insecticide-treated bednets to antimalarial drugs, which were used to great success in the 20th century in eliminating malaria in the US. In just the past few years, two new malaria vaccines – RTS,S and R21 – have been approved for young children and are now being rolled out across Africa. Adrian Hill, director of the University of Oxford’s Jenner Institute, has said we could have a malaria-free world by 2040.
But that date isn’t set in stone: malaria could be eradicated earlier or linger on for longer, depending on the efforts of governments, philanthropists, scientists, and healthcare workers. First and foremost, this means funding the production of more malaria vaccine doses and vaccinating as many children in Africa as possible as quickly as possible.
The stakes for the United States and the world are too high to keep delaying. As the planet warms, the threat of resurgent malaria in Florida and the southeast increases, while every year 600,000 more people around the world continue to meet early deaths.
The world needs to make a concerted push to wipe out malaria – and to save a thousand more lives by doing it one day sooner.