Traumatic brain injury
Out of the 1.4 million people who sustain traumatic brain injuries (TBI) each year in the United States, only 50,000 people will die, according to the Centers for Disease Control and Prevention. On March 18, actress Natasha Richardson, 45, passed away due to injuries from a blunt impact to the head she sustained while skiing in Montreal. Most TBIs -- 28 percent -- occur after a fall, and a person with a mild TBI may remain conscious and experience headache, confusion, lightheadedness, slurred speech, fatigue and trouble with memory, according to the National Institute of Neurological Disorders and Strokes. In rare instances, such as the case with Richardson, massive brain swelling may be delayed, which can postpone symptoms and may explain why Richardson was lucid up to an hour after the fall. If patients do not show immediate indications of trauma, doctors are able to diagnose bleeding and swelling of the brain with a CAT scan. Nearly half of all patients with severe injuries will need surgery to remove or repair ruptured blood vessels or bruised brain tissue.
Jim Spellman, WireImage
The flu might seem like merely an annoyance, easily cured by a week of bed rest, but the virus often isn't so innocuous. Historically, killer influenza pandemics have overtaken the nation and world. The 1918 outbreak had a death toll 10 times higher than World War I. Today, barring an epidemic, influenza can still prove deadly for the very old and the very young. In fact, your lifetime risk of dying from influenza is one in 63, according to the Centers for Disease Control.
Albinism, a genetic mutation in which the skin, eyes and hair lack the melanin that normally provides pigmentation, has proven to be a dangerous trait in the African nation of Tanzania in recent years due to a popular belief that blood and body parts from albino people will bring prosperity and luck, according to the BBC. Among East Africans, rates of albinism are as high as one in 1,000, according to a survey conducted by the World Health Organization. In the United States, about one in 17,000 have the mutation, according to the National Organization for Albinism and Hypopigmentation.
Methicillin-resistant Staphylococcus aureus bacteria, known as MRSA, can cause life-threatening infections. Once considered a health risk only in hospitals or nursing homes, the bacteria have more recently been contracted in common settings like the gym. The lifetime risk of dying of a MRSA infection in 2007 was one in 197, according to the CDC. Staph skin infections begin as small red bumps that turn into painful sores; the bacteria also can invade the body, passing into the bones, bloodstream and lungs.
Polydactyly, or being born with extra digits, is more common than you might think, especially among African-Americans. Approximately one in 100 African-American babies are born with one or more extra fingers or toes, while one in 1,000 Caucasians has the condition, according to doctors from the University of Washington Medical Center's Clinical Genetics Center and Harrison Regional Medical Center. Sometimes polydactyly can occur with other birth defects, but often the baby is otherwise perfectly healthy and normal.
The odds of a baby being born with only one eye or with one or both eyes abnormally small are about one per 10,000 births, according to the International Children's Anophthalmia and Microphthalmia Network. These conditions are called anophthalmia and microphthalmia, respectively. There is no treatment that can restore vision to the affected eye, but most children can be fitted with an artificial eye to make the face appear more normal.
Breast and skin cancer
There's no doubt that breast cancer can be devastating, but how does a woman's risk of breast cancer compare to the risk of of non-melanoma skin cancer, the most common type of cancer? Although risk varies based on factors like gender, skin color and sun exposure, the odds of a woman developing breast cancer by age 25 are one in 20,000; by age 85 that risk rises to one in eight, according to the Susan G. Komen Breast Cancer Foundation. But it's estimated that up to one-half of people in the U.S. who live to be 65 years or older will develop non-melanoma skin cancer at least once, according to the National Cancer Institute.
Heart disease and stroke
The lifetime risk of dying of heart disease -- one in five -- dwarfs the previously mentioned statistics. So does the risk of passing away from a stroke: one in 24, according to the CDC. The main risk factors for these conditions? They are, among others, smoking, being overweight and having high blood pressure and high cholesterol. So while there is plenty of danger outside your control, perhaps the best bet for a long life just might be the old standbys: eating healthfully, exercising and managing stress.
Today's experts suspect that former President Abraham Lincoln may have had Marfan syndrome, a disorder of the body's connective tissue. Approximately one in 5,000 people in the U.S. are born with this hereditary syndrome, according to the National Marfan Foundation. Often characterized by a very tall, thin build -- like Lincoln's -- and extremely flexible joints, Marfan usually affects many of the body's systems, such as the heart, lungs and nervous system, and can increase the risk of a tear or rupture of the aortic artery.
Mathew Brady, AP
HIV from a blood transfusion
Receiving a blood transfusion may be safer than ever, thanks to federal guidelines about who can donate and procedures to screen for blood-borne diseases. In fact, the risk of contracting human immunodeficiency virus, or HIV, from a blood transfusion, has dropped to between one in 1.4 million and one in 1.8 million. In 1995, that figure was between one in 450,000 and one in 660,000, according to the University of California-San Francisco.