There were 216,000 global cases of leprosy, an ancient and disfiguring disease, in 2013. CHANDAN KHANNA/AFP/Getty Images
In the 19th century, scarlet fever was a common killer in Europe. In 2016, nearly 20,000 cases were reported in the United Kingdom -- the biggest increase in 50 years.
Scarlet fever is just one disease that many have forgotten but that is by no means gone, despite our best efforts to eliminate it. Badobadop/Wikipedia
Though it's often thought of as a medieval disease, the World Health Organization reports 1,000 to 3,000 global cases of plague every year. The US averages seven new human cases a year, mostly in the Southwest. Pictured, a patient with gangrene and necrosis, caused by plague. CDC / Dr. Jack Poland
This 19-year-old girl in Neijiang, China, is being carried in a basket because she has rickets. Rickets is caused by a lack of vitamin D, which we get from sunlight. Experts believe rickets is making a comeback in developed countries because of the use of sunscreen and less time spent outdoors. China Photos/Getty Images
Gout was once known as the "disease of kings" because of its links to excessive food and alcohol consumption. These days, unhealthy lifestyles are behind an increase in gout in developed countries.
The deadly disease diphtheria affects the nose and throat. Vaccinations mean it is now rare in developed countries, but in 2011, nearly 5,000 cases were reported to the WHO, with many more probably unreported. NOAH SEELAM/AFP/AFP/Getty Images
TB, or tuberculosis, is one of the top 10 killers in the world, according to the WHO. In 2016, 10.4 million people around the globe contracted tuberculosis, and more than 1.7 million died. Ninety-five percent of those deaths were in developing countries. Spencer Platt/Getty Images/File
Vaccination programs mean polio is on the verge of extinction -- but there are still cases in Afghanistan and Pakistan.Courtesy UNICEF