A gold medal of Alexander the Great, wearing the scalp of an elephant (Michel Setboum/Getty Images)

Who loves a good mosquito bite? No one I know, although I used to concoct some elaborate bite remedies in my younger days (most of which involved precise quantities of different soaps, lotions and shampoos and none of which worked). But mosquitoes aren’t just an itchy pain — they also happen to carry a little parasite that can give you malaria, a disease that hits 500 million people each year and kills 1 million of them. And make no mistake, this mosquito-borne disease has made its mark on history.

Maybe you’ve heard of Alexander the Great? He managed to conquer most of the known world (well, known to the Greeks) and who knows what else he would have accomplished had he not died at the age of 32. (What-if historians love to debate this question.) His death occurred after two weeks of fighting fever. But what was it? Some have posited that he was poisoned by political rivals, but one convincing possible cause of death is malaria contracted in the marshes outside Babylon, according to at least one Alexander expert. Alaric, king of the Visigoths, suffered a similar fate — but not before he sacked Rome. Is malaria what halted Attila the Hun and Genghis Khan? Some historians say yes (a different kind of David and Goliath story). And that’s not all — malaria has been attributed as the cause of death to famed missionary and explorer David Livingstone as well as the painter Caravaggio, so celebrated for his studies in chiaroscuro (although modern reports often chalk up his demise to typhus instead). We know for a fact that Gandhi and John F. Kennedy both had bouts with the disease.

It probably didn’t help that for much of history, malaria was thought to be caused by the bad air that lurked around  swamps and marshes. Tourists were told by some doctors to avoid places like Venice at certain times of year altogether, although the Italians were the first to realize that draining standing water kept malaria at bay. It wasn’t until the late 1800s that we first started to get some answers, when Alphonse Laveran discovered that a parasite was involved. Army surgeon Ronald Ross is the one who gave us a concrete link between mosquitoes and these protozoan parasites.

So if you’re at a 4th of July picnic this weekend, give thanks for your citronella candles — and modern medicine.

And if you want to read more about the creepy crawlies that like to live off of you and your blood (and I’m the HowStuffWorks health editor, so I do), try the Monsters Inside Me site from Animal Planet. My favorite nightmarish article might be from our own Robert Lamb: 5 Ways Parasites Hijack Their Hosts.