Using a tiny scrap of long-preserved tissue, researchers from the Ancient DNA Centre at Ontario's McMaster University have managed to map out the genome of the cholera strain that ravaged the globe in the early 19th century, in the second of seven pandemics linked to the disease. The research confirms that the strain was the same as the "classical" Vibrio cholerae bacterium responsible for the first pandemic, and demonstrates that the disease itself is pretty young, at less than 5,000 years old, the New York Times reports. Scientists once thought it was as much as 50,000 years old.
Because cholera never reaches the bones, researchers couldn't collect DNA from skeletons—as they did when unlocking the Black Death's genome in 2011. Thankfully the Mütter Museum in Philadelphia had the intestines of several cholera patients preserved in wax-sealed jars. The museum let researchers take stamp-sized samples from three jars, and one, bottled in 1849, contained enough DNA to sequence, the Canadian Press reports. "It's fantastic to be able to actually study the evolution of these pathogens in real time," the senior author said. Researchers were drawn to cholera because it's still a threat today—although it's evolved into a less-deadly strain known as El Tor.