South Korea on Friday started culling thousands of poultry after a preliminary test indicated the first possible outbreak of bird flu since 2011, officials said.

A suspected case of avian influenza was reported Thursday at a poultry farm in Gochang in North Jeolla Province, some 300 kilometers (187.5 miles) southwest of Seoul, the agricultural ministry said.

Beijing's skyscrapers receded into a dense gray smog Thursday as the capital saw the season's first wave of extremely dangerous pollution, with the concentration of toxic small particles registering more than two dozen times the level considered safe.

The air took on an acrid odor, and many of the city's commuters wore industrial strength face masks as they hurried to work.

Men who consume more than two alcoholic drinks per day while in middle age may speed up their memory loss in later life by up to six years, said a study Wednesday.

However, there were no differences in memory or mental function between non-drinkers and those who drank less than two drinks, or 20 grams per day, said the findings in the journal Neurology.

U.S. regulators said Wednesday they are urging doctors to cease prescribing drugs that contain more than 325 milligrams of acetaminophen per tablet due to concerns over liver damage.

Prescription painkillers such as Vicodin and Percocet, can contain acetaminophen and may be dangerous if taken with other popular pain-relievers, like Tylenol, or with alcohol.

Clinical trials show that a combination of pills, one still in the experimental phase and one that was just approved for the U.S. market, are effective at curing hepatitis C, researchers said Wednesday.

However, the cost of the treatment is expected to be at least $80,000 per year, making it out of reach to many of the 150 million people chronically infected with the liver disease worldwide, experts have said.

About 50,000 people died on Brazilian roads last year, down 10 percent from 2012, according to police estimates published Tuesday in local media.

A traffic police report obtained by the O Globo daily logged 8,375 deaths or 23 per day and 103,075 injuries in 185,877 accidents on federal motorways alone in the Latin American giant.

Two men have died of swine flu in northern Spain, where an outbreak of the H1N1 virus has left over 40 people in hospital, officials said Tuesday.

Laboratory tests confirmed that the virus killed a 62-year-old man, who died Saturday in a hospital in Cantabria, the regional government said.

Panama will try to control a dengue outbreak that has claimed six lives this year by releasing transgenic mosquitoes to render infertile female transmitters of the disease, officials said Tuesday.

Health Ministry director Carlos Galvez told Agence France Presse the technique has "shown promise" in Brazil and the Cayman Islands.

New Zealand health authorities were trying to track down hundreds of passengers on Wednesday who may have been exposed to measles on a Singapore Airlines flight at the weekend.

One passenger on the flight, which landed in Auckland on Sunday night, is now known to have been infected with the highly contagious virus.

A Hong Kong man infected with the deadly H7N9 bird flu died late Monday, less than a week after he was confirmed to be infected with the deadly virus, authorities said.

The 65-year-old man was the second person to die from the virus in Hong Kong, and the third reported case of H7N9 infection.