 And in some severe cases, it can cause people's blood vessels to leak, and it can lead to shock and even death. Not good. Okay, I said the CDC is warning about risk in the United States. How severe is that risk? Who should be worried? Yeah, so it really depends on where you live. The risk is not spread equally across the country. So far this year, there have been about 2,000 cases in the U.S., and most of those cases have been in Puerto Rico, where dengue is endemic.