The World Health Organization is urging greater cooperation among nations to tackle the growing number of cross-border threats to public health.
To mark World Health Day Saturday, the WHO issued a report that warns of emerging international threats to health security.
The report says infectious diseases such as HIV/AIDs, Ebola, the SARS (Severe Acute Respiratory Syndrome) outbreak in Asia, and human cases of the H5N1 bird flu have emerged in unprecedented numbers.
The WHO says natural disasters, environmental change, bioterrorism and chemical spills also pose major challenges.
WHO Director-General Margaret Chan said countries have to share responsibility and take pre-emptive action against such threats.
As part of that effort, the Geneva-based U.N. body has revised its international regulations to help countries identify and respond earlier to health challenges.