12 Deadly Diseaes Cured in the 20th Century, 8-9

Once painful and debilitating diseases, polio and tetanus are now treatable thanks to advances in medicine. Read on and find out more about the cures for these diseases.

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.

Read on to find out how the WHO and the CDC have nearly eradicated once fatal diseases such as yellow fever and small pox.