A dangerous disease spread by mosquitoes might be surging in the United States. Surveillance data from the Centers for Disease Control and Prevention shows a sharp rise in cases of dengue. CDC scientists detailed their findings in a report published this month. In 2024, there were nearly 4,000 reported cases of dengue within the U.S., a record high and well above the typical yearly average. Though most of these cases were travel-related, the risk of local transmission seems to be increasing over time, the researchers say. “Dengue is a public health threat to persons of all ages,” they wrote in their paper, published in the Morbidity and Mortality Weekly Report (MMWR). ‘Bone-breaking’ pain Dengue is a mosquito-borne viral disease. Though most initial infections cause no symptoms, about a quarter of people will experience flu-like illness. Some can also develop pain so excruciating that it’s been compared to breaking a bone, leading to its nickname of “breakbone fever.” Between 1% and 5% of people with dengue can further experience severe, life-threatening complications like internal bleeding and shock. There are four major serotypes of the dengue virus, and surviving an infection only provides immunity to that specific type. Catching a second infection from another type of the virus raises the risk of severe dengue.