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10 Health Conditions That are More Common Than You Think

An Afghan woman and her grandson sit outside their house after a return from a reguee camp. Each year, more than 250,000 Afghans are affected with leishmaniasis, one of the 10 diseases on our list. See staying healthy pictures for preventive care.
Paula Bronstein/Getty Images News/Getty Images

Public health advocates work to spread education about the threat of HIV. Advocacy groups raise awareness about leukemia and breast cancer. And healthcare workers worldwide work with major media providers to alert us to the pandemic potential of the H1N1 flu virus.

But there's a lot more out there that can affect our health.

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The world is filled with diseases and health conditions that, although not front-page news, affect millions of people. Some target poor or underdeveloped parts of the world. Others are common in the U.S., but since they're not life-threatening don't receive the same amount of attention as HIV (which affects 33 million people worldwide and kills about 2 million each year) or breast cancer (where 1.3 million are diagnosed annually worldwide and about 41,000 die each year)[sources: UNAIDS, Imaginis]. The World Health Organization's (WHO) Neglected Tropical Diseases (NTD) program works to raise awareness of -- and promote treatment for -- the most destructive of these diseases.

Unexpected health conditions can strike anywhere. Here are 10 health conditions that are far more prevalent than you may have realized. Can you guess what they are?

People praying for relief from the bubonic plague, also known as the Black Death, circa 1350.
People praying for relief from the bubonic plague, also known as the Black Death, circa 1350.
Hulton Archive/Getty Images

There's a reason the term "plague" has become a catch-all description for something that devastates. The plague bacterium, Yersinia pestis, is arguably one of the deadliest diseases on the planet, having caused an estimated 200 million deaths over the course of recorded history [source: Perry]. Symptoms include fever and chills, swollen lymph nodes and muscle aches [source: Mayo Clinic].

Plague pandemics have swept through the inhabited world for centuries, and historians have divided the outbreaks into three pandemics. The Justinian Plague erupted in the Mediterranean from 541 AD to 700 AD. The infamous Black Death killed roughly 40 percent of Europe's population in the 14th century. And the third plague pandemic, which started in Asia in the mid-1850s, spread to every continent but Australia. Antibiotics tempered plague in the 1950s, but it still appears in isolated outbreaks; technically, the third plague pandemic is still underway [source: Perry].

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The WHO documents 1,000 to 3,000 cases of plague every year [source: CDC]. And as people encroach on once-wild areas, they are increasingly likely to come into contact with plague-bearing animals and the fleas that transmit the disease through their bites.

Plague can be treated if caught early enough, but eradicating the disease would be impossible: With the ability to affect a variety of mammals, plague is a disease that can strike, cause great suffering, and then seemingly vanish into thin air.

Eating candy regularly and brushing your teeth infrequently is a sure-fire recipe for tooth decay.
Eating candy regularly and brushing your teeth infrequently is a sure-fire recipe for tooth decay.
Nisian Hughes/Digital Vision/Getty Images

Tooth decay takes the cake as the most widespread disease on this list: According to the CDC, half of the 12- to 19-year-olds in the U.S. have tooth decay, and one quarter of all Americans aged 65 or older have lost all their teeth to the disease.

As any dentist will tell you, tooth decay comes from a combination of the mouth's natural bacteria and the leftovers of sugary food that remain on the teeth. The bacteria eat the sugars, producing acid that wears away the hard outer enamel of the teeth. Eventually, this can lead to cavities, periodontal infections and gum disease [source: ADA].

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Preventing tooth decay can be as simple as brushing and flossing every day, or as sophisticated as sealing tooth enamel with acrylic sealants. On a wider scope, communities can reduce tooth decay by adding fluoride to their drinking water. However, only 27 U.S. states provide treated water to the majority of their residents, and rates of dental care are drastically lower for low-income populations than for middle- and upper-income groups [source: CDC]. With two-thirds of U.S. children from low-income families experiencing some level of tooth decay, we're a long way from wiping out this health condition.

Also known as blinding trachoma, this disease is one of the most prevalent causes of blindness in the world. Researchers estimate that 500 million people are affected by the highly contagious disease, with 7 million to 9 million of them going blind from the effects of repeated infection. The disease is found worldwide, with its highest concentrations in the Southern Hemisphere [source: Mayer].

Trachoma is caused by a strain of chlamydia, the bacterium that causes a widespread sexually transmitted disease of the same name. Trachoma infects the inner eyelid, causing inflammation and swelling that can turn the eyelashes until they rub against the eye. This rubbing is what causes the blindness; it scuffs and scratches the cornea until it grows too cloudy to see through [source: WHO]. The infected eye releases a discharge onto towels, skin, and insects like eye-seeking flies. Since trachoma is highly asymptomatic (many infected people show no symptoms), it's easy for a person to spread the disease without even knowing he or she is a carrier.

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In areas where the disease is prevalent, as many as 90 percent of local children may carry trachoma [source: WHO]. This statistic, along with the disease's easy spread through hands, towels and simple contact between parent and child, mean trachoma is a difficult adversary for the world's public health crusaders.

The sun gives us warmth and light, but it also can lead to the most widespread form of cancer on the planet: skin cancer.

The American Cancer Society breaks skin cancer into three types, based on the cells that become cancerous. Melanoma is a cancer of melanocytes, the cells that make the melanin that gives skin its color. It's perhaps the best known of the three, due in part to its lethality: Melanoma can move to other parts of the body and eventually lead to death [source: ACS].

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But the other two skin cancers, basal and squamous cell skin cancer, account for the majority of cancer cases worldwide. Worldwide, more than 2 million new cases are diagnosed each year [source: ACS]. These are not highly lethal cancers -- only about 2,000 people die from them each year -- but treatment can range from uncomfortable surgery to the removal of tumors to chemotherapy, which can cause inflammation, scarring and other unpleasant symptoms [source: Mayo Clinic].

Thankfully, skin cancer prevention is not difficult. It simply involves protecting your skin from the sun using hats, clothing and sunscreen [source: ACS]. Skin cancer truly fits the cliché, "An ounce of prevention is better than a pound of cure."

Fascioliasis used to be considered a livestock disease. It originated in animals that waded, grazed and defecated in pools where this large (up to 7 centimeters long) flatworm lived for parts of its life cycle. But in recent decades, the disease has increasingly appeared in humans, where it can cause debilitating liver disease. The fascioliasis flatworm has a multi-stage, complex life cycle:

  • On contact with water, flatworm eggs hatch into larvae called miracidia.
  • The miracidia seek out freshwater snails and burrow into their flesh.
  • Inside the snail, the parasites change form three times, eventually becoming free-swimming cercariae.
  • The cercariae attach to water plants, where they form cysts called metacercariae.
  • When livestock or humans eat the cyst-infected water plants, the metacercariae hatch into excysts, which migrate through the host's digestive tract to the liver.
  • There, the excysts metamorphose into adult flatworms; their waste and debris can clog the liver's bile ducts and cause severe tissue damage.

[source: DPDx].

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The WHO considers fascioliasis a neglected tropical disease (NTD). Although it is relatively easy to treat with drug therapy, the fact that it's most common in rural and developing parts of the world means that its victims often do not have access to adequate care. Through partnership with drug companies, the WHO is working to overcome this inequity and drive fascioliasis out of its human hosts for good [source: WHO ].

An Afghan mother holds her son who has leishmaniasis as they wait for treatment at the Health Net Clinic in Kabul, Afghanistan.
An Afghan mother holds her son who has leishmaniasis as they wait for treatment at the Health Net Clinic in Kabul, Afghanistan.
Paula Bronstein/Getty Images News/Getty Images

Another big hitter on the WHO's NTD list is leishmaniasis, one of the biggest health threats on the planet. Some 12 million people are infected with the disfiguring parasite, but it threatens the health of 180 million more in 88 countries around the world. [source: WHO]

Leishmaniasis is caused by protozoan parasites, tiny single-celled creatures that are carried from person to person by sand flies. After entering a host through an infected fly's bite, the parasites cause one of three forms of disease:

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  • Cutaneous leishmaniasis infects the skin, causing open sores that can last for years in severe cases.
  • If left untreated, cutaneous leishmaniasis can infect the mucous membranes of the mouth and nose, causing mucosal leishmaniasis. This form of the disease can destroy the tissue and cartilage in the mouth and nose.
  • The parasites can also infect internal organs. This form of the disease, known as visceral leishmaniasis, can cause weight loss, swelling in the liver and other organs, and is often fatal.

[source: Markle]

Physicians do not treat cutaneous leishmaniasis, since it will eventually heal. It is usually only treated if it has the potential to turn into mucosal leishmaniasis. Visceral leishmaniasis is often treated with medicines containing the metal Antimony, but some strains of the disease appear to be growing resistant to the drug [source: NIAID]. Given the number of people threatened by this disease, that development is a worrying turn in leishmaniasis' long history with mankind.

This entry on the list is a little different from the rest, but it still has a significant -- though hidden -- effect on the population. "Rare disorder" is a classification given to diseases that afflict 200,000 or fewer people in the United States. Compared to other diseases on the list, that isn't a lot.

But combine the roughly 6,800 rare disorders together, and there are 25 million to 30 million affected people in the U.S. [source: NIH] And given the dynamics of disease research and advocacy, where patient population size can dictate which diseases get attention from drug makers, that's a large section of the population whose lives are disrupted by possibly untreatable diseases. Some of the diseases on the list are well known, such as certain types of muscular dystrophy.

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But politics has become a saving grace for some people afflicted with rare disorders. Thanks to grassroots advocacy by a network of families with these diseases, Congress passed the Rare Diseases Act of 2002 and the Rare Diseases Orphan Product Development Act, also in 2002. These pieces of legislation provide funding for research on new ways to treat these diseases. Without government intervention, drug makers would have little financial motivation to produce medicines for such small patient groups [source: NORD].

Finding treatment for these rare disorders is a slow process. But thanks to a Social Security Administration initiative in 2008, patients with one of 25 rare disorders can use a streamlined process to obtain Social Security benefits, easing their financial burden as they wait for a cure [source: NIH].

Patients receive treatment for water borne diseases at the International Centre for Diarrhoeal Disease Research, Bangladesh in 2007 in Dhaka, Bangladesh. A flood set off a huge outbreak of cholera.
Patients receive treatment for water borne diseases at the International Centre for Diarrhoeal Disease Research, Bangladesh in 2007 in Dhaka, Bangladesh. A flood set off a huge outbreak of cholera.
David Greedy/Getty Images News/Getty Images

The name "cholera" may invoke images of Charles Dickens' fictional slums, but when a natural disaster knocks out public water supplies anywhere in the world, you can bet public health officials are on the lookout for this fast-killing disease.

Cholera outbreaks kill about 120,000 people a year, but they infect 3 million to 5 million people per year. It turns out that cholera stays asymptomatic (causing no symptoms or harm), in about 75 percent of its hosts. The unknowing carriers pass the bacterium through their feces, which can contaminate water supplies and rapidly infect entire communities [source: WHO].

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When cholera does turn virulent, the results are swift and horrible. Victims suffer acute, watery vomiting and diarrhea, which can dehydrate them to lethal levels in a matter of hours. Antibiotics and oral or intravenous (IV) hydration can save victims, but these remedies can be difficult to come by after a flood, earthquake or other natural disaster that leaves available drinking water open to fecal contamination [source: National Library of Medicine].

Communities that prepare disaster response plans can develop strategies for getting clean water in an emergency, thereby preventing cholera outbreaks. But given the unpredictable nature of natural disasters, it's only a matter of time before an earthquake or typhoon once again leaves a community vulnerable to this ancient killer.

Singer George Michael fell asleep at the wheel of his car back in May 2006, causing a massive traffic jam. After he was awoken by a member of the public, he drove away, hitting a traffic divider.
Singer George Michael fell asleep at the wheel of his car back in May 2006, causing a massive traffic jam. After he was awoken by a member of the public, he drove away, hitting a traffic divider.
News International/Wire Image/Getty Images

Sleep researchers suggest that most adults need between seven and eight hours of sleep every night to maintain good health. But research has also shown that, in the last 20 years, there has been a spike in the number of adults who regularly get fewer than six hours of sleep a night [source: Colten]. At least 40 million Americans experience serious sleep disorders each year, and a further 20 million have occasional sleeping problems [source: NIH]. The CDC reported that 11 percent of Americans in their study said they did not get a single day of sufficient sleep in the previous month.

Sleep research links sleep deprivation to diseases like obesity, heart disease, depression and alcoholism [source: Colten]. Drowsy drivers' reduced reaction times and vigilance has been compared to that of drunk drivers [source: Powell]. A study published in 2008 in the Journal of Clinical Sleep Medicine suggests that as little as 15 to 30 minutes' more sleep per night helped teenagers reduce their number of car accidents over the course of a school year [source: Danner].

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The evidence of sleep's importance is relatively clear; so why does this problem persist in our educated society? One could argue that society itself, especially the Western culture that praises nonstop drive and ambition, prevents us from catching up on our sleep. Changing that culture would take widespread public education, something that, unlike recovery from sleep loss, won't happen overnight.

An Egyptian banded cobra cleverly blending in with its surroundings -- and making the chance of snakebite more likely.
An Egyptian banded cobra cleverly blending in with its surroundings -- and making the chance of snakebite more likely.
altrendo nature/Stockbyte/Getty Images

You didn't see this one coming. But like the perpetrators of this widespread health problem, snakebite slithers onto the list as a condition that affects a surprisingly large number of people.

The WHO's NTD program estimates 421,000 people are envenomed, or bitten by poisonous snakes, each year, with 20,000 dying from the poison. The lack of accurate records in rural areas, however, leads some experts to put those figures much higher: 1.8 million envenomings and 94,000 deaths per year. [source: WHO]

The envenomings are disproportionately frequent in poorer countries, which suffer a double-whammy: Many developing countries are in regions where very poisonous snakes, such as the cobra family, are endemic, and those same regions often lack the infrastructure to get antivenin, an antibody drug that counteracts the venom, to bite victims in time to save their lives [source: WHO].

This is not a simple case of making enough of one drug to treat snakebites around the globe. Antivenin is made by injecting the venom of a specific snake species into a horse or sheep, extracting the antibodies, and then purifying them for human use. The antivenin for a diamondback rattlesnake from the American Southwest, for example, would be useless for a patient bitten by a spectacled cobra in India [source: U of Maryland]. One could argue that, unless lab infrastructure gets much better in developing countries soon, snakebite will be a constant threat for years to come.

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