Leaders from the U.S., China, India and South Africa have reached a "meaningful agreement" on combating global warming at the international climate summit in Copenhagen, but many officials say the deal fell short of expectations. Ray Suarez reports.

The U.S. worked Thursday at salvaging an agreement at the U.N. summit on climate change. It took the form of a major financial commitment and new pressure on China to cooperate. Ray Suarez reports from Copenhagen.

Special correspondent Fred De Sam Lazaro looks at reducing black carbon emissions in North India, where the simple act of cooking can be dangerous for the environment and lung health.

Protesters outside the Copenhagen climate change summit clashed with police on Wednesday as more than 100 world leaders made their way to the Danish capital. Negotiators continue to battle over reaching a climate agreement in the conference's waning days.

Among the divisions rippling through the ongoing climate talks in Copenhagen, the U.S. and China have clashed over financing and enforcing emissions cuts. Ray Suarez reports. Developing nations and humanitarian groups have tried to express the urgency they are seeing on the ground in places that are already experiencing negative effects of climate change.

While the world meets in Copenhagen to discuss a climate deal, climate change impacts on civilization can already be seen in droughts and food shortages in some of the world's poorest and most vulnerable areas. Two food security experts explain how climate change and food security connect.

Efforts to craft a climate change deal in Copenhagen are moving slowly as world leaders clash on key issues. Ray Suarez reports from the Danish capital.

What is known about the current H1N1 influenza outbreak? How is the government preparing for the next big threat? Join the PBS NewsHour’s Ray Suarez for an exploration of the science and policy of this year’s swine flu pandemic, from federal vaccination headquarters to big city hospital emergency rooms.

In an interview with Gwen Ifill, EPA Administrator Lisa Jackson explains the decision to declare greenhouse gases a danger to human health.

In Mexico City, where schools and businesses were shuttered during the first H1N1 outbreak last spring, the initial fear and confusion surrounding the virus has lifted, but health officials warn that young children are being unexpectedly hard hit this flu season.

The State Department released its five-year global AIDS strategy Tuesday, emphasizing building countries' abilities to manage their own epidemics, but disappointing advocates by not including a budget or recommending a bolder treatment target.

The White House has finally named its USAID head nominee, after 10 months of a leadership vacuum that prompted public statements of frustration from Secretary of State Hillary Rodham Clinton. President Barack Obama has chosen Rajiv Shah, 36, a doctor and recently-appointed senior official at the Department of Agriculture.

U.S. health officials are dealing with shortages and production delays of H1N1 vaccine, but stand by the choice not to opt for vaccine boosters, called adjuvants, that could stretch supply of H1N1 vaccine, but are not licensed in the United States.

Healthy pregnant women had a good immune response after one dose of the H1N1 vaccine, but young children should get two doses for optimal protection, according to National Institute of Allergy and Infectious Diseases trial results released Monday.

Foreigners infected with HIV will be allowed to travel and immigrate to the United States without restriction, President Barack Obama said Friday, announcing the repeal of a twenty-year-old travel ban.

On the Asian island of Borneo, the Asri Clinic doesn't take credit cards. Instead, the clinic accepts payments that improve the local ecosystem, be it seedlings for replanting, eggshells for composting, even manure. Fred de Sam Lazaro reports.

Many poor or urban communities in the United States are dealing with potentially fatal diseases and parasites normally considered problems of the third world and developing countries. NewsHour correspondent Jeffrey Kaye looks at these “neglected diseases” that get little attention in the U.S. but affect hundreds of thousands of citizens each year.

The Center for Disease Control and Prevention said Friday that the H1N1 flu's effects have already matched those of the seasonal flu. Ray Suarez reports.

Many people have been reluctant to receive the H1N1 flu vaccine. But others are scrambling for a limited supply of doses. Betty Ann Bowser reports.

Many people have been reluctant to receive the H1N1 flu vaccine. But others are scrambling for the limited doses available now, leaving hospitals and clinics throughout the nation overwhelmed with vaccine-seekers. Betty Ann Bowser reports from a Rockville, Md. clinic.