12 Deadly Diseases Cured in the 20th Century

1. Chicken Pox

Before 1995, a case of the chicken pox was a rite of passage for kids. The disease, caused by the varicella-zoster virus, creates an itchy rash of small red bumps on the skin. The virus spreads when someone who has the disease coughs or sneezes, and a nonimmune person inhales the viral particles. The virus can also be passed through contact with the fluid of chicken pox blisters. Most cases are minor but in more serious instances, chicken pox can trigger bacterial infections, viral pneumonia, and encephalitis (inflammation of the brain).
According to the Centers for Disease Control and Prevention (CDC), before the chicken pox vaccine was approved for use in the United States in 1995, there were 11,000 hospitalizations and 100 deaths from the disease every year. Many countries do not require the vaccination because chicken pox doesn't cause that many deaths. They'd rather focus on vaccinating against the really serious diseases, so the disease is still common.

While chicken pox is still a relatively common occurrence, diseases like malaria and diphtheria seem to have been wiped out ages ago.

2. Diphtheria

Diphtheria is an infection of the bacteria Corynebacterium diphtheriae and mainly affects the nose and throat. The bacteria spreads through airborne droplets and shared personal items. C. diphtheriae creates a toxin in the body that produces a thick, gray or black coating in the nose, throat, or airway, which can also affect the heart and nervous system. Even with proper antibiotic treatment, diphtheria kills about 10 percent of the people who contract it. The first diphtheria vaccine was unveiled in 1913, and although vaccination has made a major dent in mortality rates, the disease still exists in developing countries and other areas where people are not regularly vaccinated. The World Health Organization (WHO) estimates that worldwide there are about 5,000 deaths from diphtheria annually, but the disease is quite rare in the United States, with fewer than five cases reported each year.

3. Invasive H. Flu

Invasive H. flu, or Hib disease, is an infection caused by the Haemophilus influenzae type b (Hib) bacteria, which spreads when an infected person coughs, sneezes, or speaks. Invasive H. flu is a bit of a misnomer because it is not related to any form of the influenza virus. However, it can lead to bacterial meningitis (a potentially fatal brain infection), pneumonia, epiglottitis (severe swelling above the voice box that makes breathing difficult), and infections of the blood, joints, bones, and pericardium (the covering of the heart). Children younger than five years old are particularly susceptible to the Hib bacteria because they have not had the chance to develop immunity to it. The first Hib vaccine was licensed in 1985, but despite its success in the developed world, the disease is still prevalent in the developing world. WHO estimates that each year Hib disease causes two to three million cases of serious illness worldwide, mostly pneumonia and meningitis, and 450,000 deaths of young children.

4. Malaria

This disease is a parasitic infection of the liver and red blood cells. In its mildest forms it can produce flu-like symptoms and nausea, and in its severest forms it can cause seizures, coma, fluid buildup in the lungs, kidney failure, and death. The disease is transmitted by female mosquitoes of the genus Anopheles. When the mosquito bites, the parasites enter a person's body, invading red blood cells and causing the cells to rupture. As the cells burst, they release chemicals that cause malaria's symptoms.

About 350 million to 500 million cases of malaria occur worldwide every year. About one million are fatal, with children in sub-Saharan Africa accounting for most of the deaths. Other high-risk areas include Central and South America, India, and the Middle East. Malaria is treated with a variety of drugs, some of which kill the parasites once they're in the blood and others that prevent infection in the first place. Of course, if you can avoid the parasite-carrying mosquitoes, you can avoid malaria, so the disease is often controlled using mosquito repellent and bed netting, especially in poor countries that cannot afford medications.

5. Measles

Measles is a highly contagious viral illness of the respiratory system that spreads through airborne droplets when an infected person coughs or sneezes. Although the first symptoms of measles mimic a simple cold, with a cough, runny nose, and red watery eyes, this disease is more serious. As measles progresses, the infected person develops a fever and a red or brownish-red skin rash. Complications can include diarrhea, pneumonia, brain infection, and even death, although these are seen more commonly in malnourished or immunodeficient people. Measles has historically been a devastating disease, but WHO reported in 2006 that measles mortality rates dropped from 871,000 to 454,000 between 1999 and 2004, thanks to a global immunization drive.

Until 1963, when the first measles vaccine was used in the United States, almost everyone got the measles by age 20. There has been a 99 percent reduction in measles since then, but outbreaks have occurred when the disease is brought over from other countries or when children don't get the vaccine or all the required doses. Most children today receive the measles vaccine as part of the MMR vaccination, which protects against measles, mumps, and rubella (German measles).

Read on to learn about a couple more obscure but often deadly illnesses: pneumococcal disease and whooping cough -- both of which have been cured in the 20th century thanks to science.

6. Pertussis

Whoop, there it is -- and if you suspect someone has it, move away. Pertussis, or whooping cough, is a highly contagious respiratory infection caused by the Bordetella pertussis bacteria. The descriptive nickname comes from the "whooping" sounds that infected children make after one of the disease's coughing spells. The coughing fits spread the bacteria and can last a minute or longer, causing a child to turn purple or red and sometimes vomit. Severe episodes can cause a lack of oxygen to the brain. Adults who contract pertussis usually have a hacking cough rather than a whooping one.

Although the disease can strike anyone, it is most prevalent in infants under age one because they haven't received the entire course of pertussis vaccinations. The pertussis vaccine was first used in 1933, but adolescents and adults become susceptible when the immunity from childhood vaccinations wanes and they don't get booster shots. According to the CDC, pertussis causes 10-20 deaths each year in the United States, and there were 25,000 cases reported in 2004. Worldwide, the disease causes far more damage -- about 50 million people around the world are infected annually, and WHO estimates around 294,000 deaths each year. However, 78 percent of the world's infants received three doses of the vaccine in 2004.

7. Pneumococcal Disease

Pneumococcal disease is the collective name for the infections caused by Streptococcus pneumoniae bacteria, also known as pneumococcus. This bacteria finds a home all over the body. The most common types of infections caused by S. pneumoniae are middle ear infections, pneumonia, bacteremia (blood stream infections), sinus infections, and bacterial meningitis. There are more than 90 types of pneumococcus, with the ten most common types responsible for 62 percent of the world's invasive diseases.

Those infected carry the bacteria in their throats and expel it when they cough or sneeze. Like any other germ, S. pneumoniae can infect anyone, but certain population groups are more at risk, such as the elderly, people with cancer or AIDS, and people with a chronic illness such as diabetes. The CDC blames pneumococcal disease for the deaths of 200 children under the age of five each year in the United States. WHO estimates that annually pneumococcal disease is responsible for one million fatal cases of respiratory illness alone; most of these cases occur in developing countries. There are two types of vaccines available to prevent pneumococcal disease, which the CDC recommends that children and adults older than age 65 receive.

8. Polio

Of the deadly infectious diseases for which science has developed vaccines and treatments, people are most familiar with the victory over polio. The disease is caused by a virus that enters the body through the mouth, usually from hands contaminated with the stool of an infected person. In about 95 percent of cases, polio produces no symptoms at all (asymptomatic polio), but in the remaining cases of polio, the disease can take three forms.

Abortive polio creates flu-like symptoms, such as upper respiratory infection, fever, sore throat, and general malaise. Nonparalytic polio is more severe and produces symptoms similar to mild meningitis, including sensitivity to light and neck stiffness. Finally, paralytic polio produces the symptoms with which most people associate the disease, even though paralytic polio accounts for less than 1 percent of all cases. Paralytic polio causes loss of control and paralysis of limbs, reflexes, and the muscles that control breathing.

Today, polio is under control in the developed world, and world health authorities are close to controlling the disease in developing countries, as well. Dr. Jonas Salk's inactivated polio vaccine (IPV) first appeared in 1955, and Dr. Albert Sabin's oral polio vaccine (OPV) first appeared in 1961. Children in the United States receive IPV, but most children in developing areas of the world receive OPV, which is cheaper and doesn't have to be administered by a health-care professional; however, in rare instances, OPV can cause polio.

9. Tetanus

Reproductive cells (spores) of Clostridium tetani are found in the soil and enter the body through a skin wound. Once the spores develop into mature bacteria, the bacteria produce tetanospasmin, a neurotoxin (a protein that poisons the body's nervous system) that causes muscle spasms. In fact, tetanus gets its nickname -- lockjaw -- because the toxin often attacks the muscles that control the jaw. Lockjaw is accompanied by difficulty swallowing and painful stiffness in the neck, shoulders, and back. The spasms can then spread to the muscles of the abdomen, upper arms, and thighs.

According to the CDC, tetanus is fatal in about 11 percent of cases, but fortunately, it can't be spread from person to person -- you need direct contact with C. tetani to contract the disease. Today, tetanus immunization is standard in the United States, but if you are injured in a way that increases tetanus risk (i.e. stepping on a rusty nail, cutting your hand with a knife, or getting bitten by a dog), a booster shot may be necessary if it's been several years since your last tetanus shot.

According to the CDC, since the 1970s, only about 50 to 100 cases of tetanus are reported in the United States each year, mostly among people who have never been vaccinated or who did not get a booster shot. And WHO says that globally there were about 15,500 cases of tetanus in 2005.

10. Typhoid Fever

Typhoid is usually spread when food or water has been infected with Salmonella typhi, most often through contact with the feces of an infected person. Once the typhoid bacteria enter the bloodstream, the body mounts a defense that causes a high fever, headache, stomach pains, weakness, and decreased appetite.

Occasionally, people who have typhoid get a rash of flat red spots. Because sewage treatment in the United States is quite good, the disease is very rare, and the CDC reports only about 400 cases of it annually. However, people who live in developing countries where there is little water and sewage treatment, or where hand washing is not a common practice, are at high risk. Prime typhoid fever areas are in Africa, Asia, the Caribbean, India, and Central and South America.

WHO estimates 17 million cases occur globally with 600,000 deaths each year. Despite these daunting statistics, typhoid fever vaccination is available for people who travel to high-risk areas, and the disease can be effectively treated with antibiotics. Without treatment, the fever can continue for weeks or months, and the infection can lead to death.

11. Yellow Fever

Yellow fever is spread by mosquitoes infected with the yellow fever virus. Jaundice, or yellowing of the skin and eyes, is the hallmark of the infection and gives it its name. Most cases of yellow fever are mild and require only three or four days to recover, but severe cases can cause bleeding, heart problems, liver or kidney failure, brain dysfunction, or death.

People with the disease can ease their symptoms, but there is no specific treatment, so prevention via the yellow fever vaccine is key. The vaccine provides immunity from the disease for ten years or more and is generally safe for everyone older than nine months.

Yellow fever occurs only in Africa, South America, and some areas of the Caribbean, so only travelers who are destined for these regions need to be concerned about it. WHO estimates that there are 200,000 cases of yellow fever every year, and 30,000 of them are fatal. The elderly are at highest risk of developing the most severe symptoms. Although vaccination and mosquito-eradication efforts have made a great difference, WHO says yellow fever cases are on the rise again.

12. Smallpox

Unlike other diseases on this list, which can still appear in outbreaks when vaccination vigilance weakens, smallpox has been wiped off the face of the earth, except for samples of the virus held in labs in the United States and Russia for research purposes.

Symptoms of smallpox included a high fever, head and body aches, malaise, vomiting, and a rash of small red bumps that progressed into sores that could break open and spread the virus (the virus could also be spread via contact with shared items, clothing, and bedding). Smallpox was an entirely human disease -- it did not infect any other animal or insect on the planet. Thus, once vaccination eliminated the chances of the virus spreading among the human population, the disease disappeared; in fact, the United States has not vaccinated for smallpox since 1972.

Although smallpox was one of the most devastating illnesses in human history, killing more than 300 million people worldwide during the 20th century alone, scientists declared the world free of smallpox in 1979. The naturally occurring disease has been eradicated, but fears remain about the smallpox samples being used as bioweapons.