In parts of Southeast Asia, setting a bird free from its cage is a tradition that symbolizes improving a person's soul. But public health workers are now concerned that birds in markets in the region could be spreading H5N1, the bird flu.

NewsHour correspondent Fred de Sam Lazaro reports from Cambodia about how the interaction between humans and wildlife can contribute to the spread of deadly diseases. While bird flu affects different species of birds in different ways, it kills most humans who get it.

In this report, de Sam Lazaro talks to health experts about the effort to combat bird flu in a society that is in constant contact with birds.

"A big concern here in this area is the very close proximity of people living with domestic animals and interacting with wildlife. And this can either be in the home or this can be in the market or in merit bird training. And this close proximity can be enough pressure to allow a pathogen to jump from one species to the next and then lead to a disease that otherwise may not have occurred." - Priscilla Joyner, Wildlife Conservation Society

"Once humans are infected, if they're infected with seasonal flu, that's a possibility for H5N1 to mix with the seasonal flu and to come up with a new virus that would have the potential to be a pandemic one." - Dr. Sirendes Vong, Pasteur Institute

1. What is bird flu? Con you name other flu strains?

2. How do diseases spread?

1. Are you worried about bird flu? Why or why not?

2. Swine flu made big news earlier this year. What is a major difference between how swine flu spreads and how bird flu spreads?

3. How can we best balance cultural practices and public health?