The bubonic plague. Scarlet fever. Polio. Diseases of the past, and no longer on this Earth, right?
Many old-time diseases are still present today, but fortunately many of them aren't as prevalent or dangerous as their ancestral versions. But why are these diseases still around?
For infectious diseases, a big part of it has to do with the organism in which the diseases are carried -- it's a lot easier to eradicate a disease if it's only spread from human to human, than if it's spread from animals to humans, said infectious disease expert Dr. Geoffrey A. Weinberg, a professor of pediatrics in the Division of Pediatric Infectious Diseases at the University of Rochester Medical Center.
So far, there have only been two infectious diseases that have been completely eradicated from the planet: smallpox, and the animal disease rinderpest, he said.
"Those were easier to eradicate from the world because they were single strains of organisms -- both were viruses -- and they only infected one type of creature," Weinberg told HuffPost. "Smallpox only infected humans -- it was easy to recognize, and there was only one strain of it -- so a vaccine was easily producible. All those things combine to make it something that if people get their minds together and can recognize a disease, they can eliminate it."
With illnesses like the flu, on the other hand, the virus that causes it mutates a lot and can live in a number of different organisms, including humans, pigs and birds, he said.
Take bubonic plague, for example. The disease is most commonly transmitted to humans through flea bites, and the fleas live on rodents. It's hard to completely extinguish bubonic plague in rodents and fleas, since there are so many of them around the world, Weinberg said. The same goes for spore diseases like anthrax, where it's in the soil -- "you can't get rid of that unless you concrete the entire world, because it's in the soil."
"Basically, the factors that lead to why diseases stick around, or come back, is because sometimes the germs change a little," Weinberg said. "Sometimes they're germs you can't get rid of, thats why we have to keep it suppressed by protecting people with a vaccine. Other germs, they're common and we don't know how to get rid of them. And then some germs, like influenza, are changing their coats. You're always chasing after them."
Take a look at five old-time diseases that still persist today.
Yes, the black plague -- responsible for killing 56 million people in Europe the 14th century -- is still around, but it isn't as deadly or prevalent as it was in Medieval times. Dr. Robert Gaynes, an infectious disease expert at Emory University and author of the book Germ Theory: Medical Pioneers in Infectious Diseases, said that people contract the disease when they gain access to previously undistrubed ecosystems, thereby making "these types of diseases become evident as a result of animal contact." These days, the disease is most commonly spread by bites from fleas that are infected with Yersinia pestis. When the bacteria enters into a person's skin, it leads to headache, chills, and swollen lymph glands, according to the CDC. Early treatment with antibiotics is essential for survival, as the disease can cause respiratory failure and shock if left untreated. Every year, about 1,000 to 3,000 bubonic plague cases occur around the world, with 10 to 20 of those cases in the United States, TIME reported. The first 2011 case of bubonic plague was confirmed in May in a New Mexico man. The reason is murky for why black plague seems to be less deadly today than in the Medieval times, Weinberg said, but it probably has to do with more rats and unclean living conditions back then, as well as a lack of appropriate medicines. In addition, the bacteria back then may be different from the current form, he added.
Scarlet fever was among the rash of diseases that commonly afflicted people in the 19th century (alongside yellow fever, rubella and measles), according to MedicineNet. Scarlet fever most often afflicts children, causing rash and fever. Fortunately, scarlet fever is a lot less common today than it was centuries ago, but it still can be deadly. Today, we now know that scarlet fever is just a form of group A streptococcus (strep), Weinberg said. But instead of just turning into a regular case of strep throat, scarlet fever manifests as a red skin rash. With antibiotics, the disease is easily treated, though complications can occur that can lead to sepsis (bacteria in the blood, tissue or bone), according to MedicineNet. Just this summer, Reuters reported that a Hong Kong kindergarten was closed after tests revealed that a child there may have died from scarlet fever. Scarlet fever is relatively common in that part of the world, but this year a Hong Kong health department spokesman told Reuters that there seem to be more cases of it this year than in past years.
Whooping cough, caused by the Bordetella pertussis bacteria, was a common illness among children in the early 1900s, according to HealthCentral. However, when the vaccine for whooping cough was introduced in the 1940s, cases dropped. But while whooping cough cases are still dramatically lower than 50 years ago, there are still cases that persist today possibly because the vaccine against the disease doesn't provide lasting protection later in life, Weinberg said. Another reason is that older people seem to be able to carry whooping cough in their throats without actually getting sick (due to being vaccinated at a younger age), but that whooping cough is then passed on to infants who haven't yet been vaccinated against the disease, Gaynes said. "This problem has led to a recent recommendation by [the] CDC to have adults get TDAP once as adults (it contains pertussis in the vaccine) and not just a tetanus booster, which is needed every ten years," Gaynes told HuffPost. Recent research presented just last month shows that the protection from the whooping cough vaccine is decreased dramatically once a child reaches age 8 or 9, the San Francisco Chronicle reported. Whooping cough is very contagious -- spread by cough and sneezing -- and is so named because of the sound people who have it make when they cough. Last year, 27,550 people had whooping cough in the United States, according to the CDC. The disease is the deadliest for babies, as it can lead to pneumonia, convulsions and even death.
Polio, the paralysis-causing disease that afflicted former president Franklin D. Roosevelt, isn't completely gone from the world today. However, it has been eliminated from the western world, Weinberg said. The Mayo Clinic reports that the last known case of polio in the U.S. was in 1979. Polio is still present in Afghanistan, Pakistan, India and Nigeria, where unrest and dangerous conditions can make it more difficult to get everyone vaccinated against the disease, according to the World Health Organization. Recently, the WHO reported that a dangerous strain of polio -- called wild poliovirus type 1 -- had made its way from Pakistan to China. Polio causes paralysis and can make it hard to breathe, the Mayo Clinic reported. It can even lead to death.
Gout has been known throughout history as the "disease of kings" and the "rich man's disease," as it was most commonly seem among the gluttonous rich in the 1700 and 1800s, according to the British Library. Gout is considered an ancient form of inflammatory arthritis, and is caused by metabolic disorder that has not been properly controlled. It occurs when uric acid crystals build up in tissues and fluids, thereby leading to a red, swollen joint that is very painful, according to the Centers for Disease Control and Prevention. The condition is most common in overweight men and women who have gone through menopause. Gout rates have been on the rise since the 1960s, with cases doubling between 1960 and 1990 and then continuing to rise through 2008, according to WebMD. More than 8 million Americans currently have gout. WebMD reported that the rise in gout cases may be due to people living longer, as the condition is seen in women only after they have passed menopause. In addition, "you can go years with hyperuricemia and no symptoms. But at some point, enough uric acid accumulates to have a flare-up of gout, so if you're living longer you are more likely to reach that threshold," gout expert Dr. John S. Sundy told WebMD. In addition, Gaynes speculated that it may not even be that gout rates are actually rising -- rather, detection and diagnosis may have improved throughout the years.