WHO Director-General Dr. Margaret Chan said one of the changes affecting human health was increasingly intensive poultry farming, which may account for the global spread of bird flu.

''It should not come as a surprise that we are seeing more and more disease outbreaks coming from the animal sector,'' Chan said.

She said the majority of the 39 new diseases came from animals, including Ebola, SARS, or bird flu.

Today, high volumes of people can quickly travel worldwide, meaning an outbreak or epidemic in any part of the planet is only a few hours away from becoming an imminent threat somewhere else, the report said. Over the past five years, WHO has confirmed more than 1,100 outbreaks worldwide of diseases such as cholera, polio and bird flu.

Much of WHO's annual report on the state of the world's health was designed to convince governments to adhere to new, tighter International Health Regulations, providing the basis for the world to cooperate in combating frightening diseases.

The revised health regulations came into effect in June. They govern how countries should report potentially dangerous health emergencies to WHO.

While they are meant to improve disease reporting worldwide, it is uncertain how much influence they actually have. For example, earlier this year, American officials anxiously tracked the European whereabouts of a U.S. lawyer believed to have a highly dangerous form of tuberculosis.

International officials eventually identified the roughly 127 people thought to have been exposed to his illness during two trans-Atlantic flights. But it was only after the lawyer had left Europe that U.S. officials informed WHO and other countries of the event — and they were powerless to act. The lawyer later turned out to have a less serious form of the disease.

WHO's annual report also urges countries to share viruses to help develop vaccines and to tighten domestic efforts to combat disease outbreaks.

But an ongoing battle with Indonesia, the nation hardest hit by the H5N1 bird flu, has yet to be resolved. Indonesia has been reluctant to share its samples with WHO, repeatedly demanding assurances that any pandemic vaccines developed would be affordable for developing nations.

In an effort to lure back tourists, Jakarta recently sent samples to WHO, but it is unclear whether it will continue to share.

China stopped sharing H5N1 specimens with WHO for almost a year before finally sending samples in June, while Vietnam said it sent samples but has encountered shipping road blocks.