(CNN) -- The most deadly recorded listeria outbreak and concerns about nuclear radiation after Japan's biggest earthquake made major health headlines this year, along with several notable deaths to cancer and the inspiring recovery of a Congresswoman who suffered brain injuries from a gunshot wound.
Here's a look back at some of the top stories of 2011, a year that marked major anniversaries in some of the world's most pernicious diseases -- HIV/AIDS and the "war" on cancer.
A congresswoman's recovery
2011 was barely a week old when shots rang out in a grocery store in Tucson, Arizona. U.S. Rep. Gabrielle Giffords, 40, had been shot in the head by a gunman.
The bullet passed through the left side of Gifford's brain, but she survived. A few months later, her press office began revealing photos of her progress.
In November, she gave her first televised interview, saying that she never became angry over what happened. She shrugged and said it was "life."
Nuclear fears in Japan
An 9.0-magnitude earthquake, the most powerful one to hit Japan in recorded history, led to a tsunami that engulfed parts of Honshu. It also started a meltdown at the Fukushima Daiichi's nuclear facility in northeast Japan.
Subsequent tests have detected radiation in a sample of people who live around the power plant.
Although the Japanese workers were able to achieve a "cold shutdown" at the plant in mid-December, experts say it will take perhaps decades to fully clean up the nuclear disaster. What this entails for people who live around the site remains unclear.
WHO warns of possible cancer risk from cell phones
The World Health Organization announced in May that radiation from cell phones can possibly cause cancer, adding that no adverse health effects had been established. While there are no definitive studies, the warning gave people pause about cell phone use.
A listeria outbreak in cantaloupe killed 29 people and sickened nearly 150 in the United States, making this year's outbreak the deadliest for listeria since the Centers for Disease Control and Prevention began keeping track. One woman pregnant at the time of illness had a miscarriage, according to the CDC.
The outbreak first detected in September was traced back to a Colorado farm. Unsanitary conditions at the farm's packing facility are a possible contributing cause, the U.S. Food and Drug Administration said in October.
Prostate cancer screening controversy
The question of whether prostate-specific antigen tests for prostate cancer do more harm than good stirred controversy this year.
The U.S. Preventive Services Task Force gave the PSA test a "D" rating, meaning it offers "no net benefit or that the harms outweigh the benefits."
The issue is that many of the prostate cancers that get detected are so small and slow-growing that they'll never be harmful. The screening does not determine whether the cancer is a harmful one versus the slow, harmless ones.
Most men who learn they have prostate cancer receive invasive treatment for a disease that might not have affected their health. At the same time, prostate cancer survivors say their lives were saved by the screenings.
Cancer claimed the lives of several luminaries this year: tech innovator Steve Jobs (pancreatic cancer), author Christopher Hitchens (esophageal cancer) and former heavyweight champion Joe Frazier (liver cancer).
This year also marked the 40th year since Congress passed the National Cancer Act of 1971. The legislation never mentioned the word "war," but many were optimistic that cancer would be conquered. Decades later, that naivete has faded as scientists realize the complexity of cancer.
This year, the FDA approved two drugs for melanoma: vemurafenib and ipilimumab, which was the first melanoma drug to be approved in 13 years. Seven of the 35 drugs approved by the FDA this year are advances in cancer treatment.
30 years of HIV/AIDS
It was the 30th anniversary of HIV/AIDS. The first report of the disease appeared on June 5, 1981, in the Center for Disease Control's Morbidity and Mortality Weekly Report.
Although medicine and treatment has been greatly advanced since the 1980s, the disease has killed more than 25 million people worldwide. Today, about 33 million are living with HIV/AIDS, with more than a million of those in the United States.
This year, the National Institutes of Health published the results of a study that says taking antiretroviral drugs at the onset of HIV leads to a dramatic reduction in HIV transmission.
The toll of repeated head blows and injuries loomed over football again.
One former football player killed himself after leaving a message telling his family to get his brain to the NFL brain bank. An examination of his brain showed that he had signs of a brain disease found in athletes who have been exposed to repeated brain trauma.
This year, 75 former players accused the NFL of engaging in "a scheme of fraud and deceit" and denying the link between concussion and decline. Another group of former NFL players sued the league in December, accusing the league of failing to protect them against on-the-field brain injuries.
The NFL has begun cracking down on helmet-to-helmet blows with fines and suspensions.
Health care reform
Finally, the health care reform law signed into law by President Barack Obama last year went through several legal challenges in 2011 and will head to the Supreme Court in 2012.
The Patient Protection and Affordable Care Act was passed in March 2010 by a Democratic congressional majority with the support of the president. The law faces legal challenge from 26 states, led by Florida. Those appeals have paved the way to a hearing in the Supreme Court.
This year, the CDC reported that about 2.5 million young people have received health insurance coverage as a result of health care reform measures.