Swine flu spreads to Middle East, Asia-Pacific

World health officials raised a global alert to an unprecedented level as swine flu was blamed for more deaths in Mexico and the epidemic crossed new borders, with the first cases confirmed Tuesday in the Middle East and the Asia-Pacific regions.

With the swine flu having already spread to at least six other countries, authorities around the globe are like firefighters battling a blaze without knowing how far it extends.

Symptoms include a fever of more than 100, coughing, joint aches, severe headache and, in some cases, vomiting and diarrhea.

Flu deaths are nothing new in the United States. The CDC estimates that about 36,000 people died of flu-related causes each year, on average, during the 1990s in the United States. But the new flu strain is a combination of pig, bird and human viruses that humans may have no natural immunity to.