Puerto Rico ? Dengue fever is spreading across Latin America and the Caribbean in one of the worst outbreaks in decades, causing agonizing joint pain for hundreds of thousands of people and killing nearly 200 so far this year.

The mosquitoes that carry dengue are thriving in expanded urban slums scattered with water-collecting trash and old tires. Experts say dengue is approaching record levels this year as many countries enter their wettest months.

“If we do not slow it down, it will intensify and take a greater social and economic toll on these countries,” said Dr. Jose Luis San Martin, head of anti-dengue efforts for the Pan American Health Organization, a regional public health agency.