Women are often in the dark when it comes to basic facts about sex, fertility, pregnancy and their own reproductive health, according to a U.S. study Monday.

The research was conducted by Yale University via an online survey of 1,000 women aged 18-40 from across the United States.

Taking his first faltering steps since his left leg was blown off by a landmine, Sergeant Muneer Ahmad is grim proof that the Afghan army is paying a heavy price in its war against the Taliban and struggling to care for its wounded.

Ahmad, 23, trod on a mine while fighting in the southern province of Kandahar six months ago as Afghan forces assume control of the anti-insurgent campaign after 12 years of well-funded U.S.-led NATO operations.

Scientists say two of the deadliest pandemics in history were caused by strains of the same plague and warn that new versions of the bacteria could spark future outbreaks.

Researchers found tiny bits of DNA in the teeth of two German victims killed by the Justinian plague about 1,500 years ago. With those fragments, they reconstructed the genome of the oldest bacteria known.

Hong Kong began a mass cull of 20,000 chickens on Tuesday after the deadly H7N9 bird flu virus was discovered in poultry imported from mainland China, authorities said.

Fears over avian bird flu have grown following the deaths of two men in Hong Kong since December. Both had recently returned from mainland China.

One in four nursery school children caught up in Japan's 2011 tsunami disaster has psychiatric problems, a report said Monday, with experts warning the effects could last a lifetime if left untreated.

Researchers found 25.9 percent of children aged between three and five suffers from symptoms including vertigo, nausea and headaches, with some exhibiting worrying behavior such as violence or withdrawal.

Russia on Monday imposed a ban on Australian beef byproducts such as offal over the use of a growth stimulant allowed in some nations but that Moscow considers unsafe.

The temporary restrictions also affect Belarus and Kazakhstan -- two ex-Soviet nations that are part of a Moscow-led Customs Union.

South Korea imposed Monday a 12-hour lockdown on poultry farms in three provinces to curb a spreading bird flu outbreak, banning the movement of animals, people and vehicles.

More than 640,000 poultry have already been slaughtered since the outbreak was first detected on January 16 at a duck farm in Gochang, 300 kilometers (187 miles) southwest of Seoul.

China has reportedly downgraded H7N9 bird flu in humans, dropping its description as "infectious" in new guidelines on how to deal with the disease, even as new cases spike with the onset of winter.

The National Health and Family Planning Commission described it as a "communicable acute respiratory disease" in its 2014 diagnosis and treatment protocols.

Global medical charity Medecins Sans Frontieres slammed Friday a statement by Bayer's chief executive that the giant German firm only developed its cancer drug Nexavar for people who could afford the medicine, not "for Indians".

India's controller general of patents angered Bayer in March 2012 when he authorized a local drugmaker to produce a generic copy of Nexavar, saying the German company charged a price that was too costly for most Indians.

Colombian President Juan Manuel Santos has called for a scientifically backed international effort to weigh the consequences of legalizing marijuana, urging a coherent joint policy to tackle the scourge of drugs.

"We must approach this problem internationally, otherwise we'll take it from one place to another," Santos said, speaking Thursday at the annual World Economic Forum in Davos.