A landmark clinical trial that showed HIV drugs can be as effective as condoms in preventing transmission of the virus that causes AIDS was declared Science magazine's breakthrough of the year on Thursday.

Other top achievements of 2011 included a Japanese spacecraft's return to Earth with dust from an asteroid, progress toward a malaria vaccine and discoveries about modern humans' gene links to cavemen.

The journal Science is retracting a research paper suggesting that chronic fatigue syndrome may be caused by a particular virus.

The paper was published in 2009. The authors reported finding a virus called XMRV in blood cells from patients with the syndrome. But follow-up studies found no such connection.

Taiwanese authorities said Thursday they had slaughtered nearly 1,000 pigs following the island's worst outbreak of foot-and-mouth disease in more than 14 years.

The pigs were culled earlier this week at a farm in the southern city of Tainan after showing symptoms of the disease.

Philip Morris International's decision to slash the price of its best-selling Marlboro brand by 40 percent in Senegal has left health officials and activists fuming and sparked calls to toughen tobacco laws.

PMI, when contacted by AFP, refused to explain the shock decision to cut the prices of Marlboro -- the world's top-selling cigarette sold in some 180 countries -- to 400 CFA francs (61 euro cents, 79 US cents) from 650 CFA francs.

Health authorities sought Wednesday to reassure 50,000 British women who have breast implants made by a French company at the heart of a cancer scare, saying there was no evidence of a link to the disease.

France has said up to 30,000 women there may need to remove defective implants produced by the Poly Implant Prothese (PIP) company amid cancer fears, even though no "causal link" to the disease had yet been established.

The U.S. government asked scientists Tuesday not to reveal all the details of how to make a version of the deadly bird flu that they created in labs in the U.S. and Europe.

The lab-bred virus, being kept under high security, appears to spread more easily among mammals. That's fueled worry that publishing a blueprint could aid terrorists in creating a biological weapon, the National Institutes of Health said.

People who took blood pressure medicine during a 1980s clinical trial showed longer life expectancy two decades later than people who took a placebo, a U.S. study said on Tuesday.

The randomized trial included 4,736 patients aged 60 and over who had high blood pressure. Some were given a drug called chlorthalidone and others were given a sugar pill for a 4.5 year period beginning in 1985.

Progressive deafness profoundly influenced Beethoven's compositions, prompting him to choose lower-frequency notes as his condition worsened, scientists said on Tuesday.

Beethoven first mentioned his hearing loss in 1801 at the age of 30, complaining that he was having problems hearing the high notes of instruments and voices.

John Shoemaker visited six doctors in his quest to find the best treatment for his early stage prostate cancer — and only the last one offered what made the most sense to the California man: Keep a close watch on the tumor and treat only if it starts to grow.

Very few men choose this active surveillance option. Yet Shoemaker is one of more than 100,000 American men a year deemed candidates for it by a government panel. That is because their prostate cancer carries such a low risk of morphing into the kind that could kill.

Doctors in Chile are optimistic about the survival of a 10-month-old girl who was separated from a conjoined twin who died following the surgery.

Little Maria Paz awoke for the first time since the operation nearly a week ago, and Dr. Carlos Acuna calls that "an excellent sign." He says she's been successfully switched to a common respirator and her condition is favorable.