Mosquito bites suck. Flea bites bite. And tick bites, uh, well they suck too. And according to a report from the U.S. Centers for Disease Control and Prevention released on Tuesday, these annoying bugs and the diseases they spread are getting worse.

In the CDC’s latest Vital Signs report, the agency says that between 2004 and 2016, the number of illnesses spread by these bugs tripled, for a grand total of over 640,000 cases over the 14-year period. They also report that nine new illnesses spread by these bugs have been identified in the U.S. since 2004. Officials suggest that increases in global trade and travel, as well as warmer temperatures, could have contributed to this rise in disease numbers.

“Zika, West Nile, Lyme, and chikungunya — a growing list of diseases caused by the bite of an infected mosquito, tick, or flea — have confronted the U.S. in recent years, making a lot of people sick. And we don’t know what will threaten Americans next,” CDC Director Robert Redfield, M.D., said in a statement. “Our Nation’s first lines of defense are state and local health departments and vector control organizations, and we must continue to enhance our investment in their ability to fight against these diseases.”

Ticks spread a number of diseases, including anaplasmosis, Lyme disease, and Rocky Mountain spotted fever, just to name a few. E. Peñalver

CDC officials report that diseases spread by mosquitoes, ticks, and fleas are moving into new areas nationwide as a result of overseas travel and trade, which have brought diseases like chikungunya and Zika to the U.S. since 2004. All it takes to spread these illnesses to a new place is for a few sick people inadvertently traveling to a place where mosquitoes can bite them and spread it to more people.

“All these diseases are basically a plane flight away,” Lyle Petersen, M.D., M.P.H., director of the CDC’s Division of Vector-Borne Diseases told reporters on Tuesday. He also noted that as the years go on, new diseases seem to be introduced to the U.S. more frequently. “There appears to be an accelerating trend,” he said, since West Nile virus first appeared in the U.S. in 1999, while chikungunya and Zika appeared in just the past few years.

Once the diseases are in the U.S., things really start to take off. When that happens, the CDC is tasked with tracking and stemming their spread. While the CDC scientists wouldn’t confirm or deny whether climate change was affecting the spread of these disease vector bugs, Redfield and Petersen did tell reporters that warmer temperatures expand their range and increase the length of the tick and mosquito seasons. Therefore, with warming weather, it’s reasonable to conclude that we can expect these problems to worsen.

Unfortunately, the CDC’s preparedness hasn’t kept pace with the increase in bug-transmitted diseases. Redfield and Petersen emphasize that there’s a lot left to do to improve vector control efforts all over the U.S. On a hopeful note, they say that congressional funding provided to the CDC as a result of concerns around the Zika epidemic has gone a long way toward helping ramp up efforts. Petersen reports that the CDC will help rebuild state and local vector-control programs that are in need of support, but this process will take time.

In the meantime, the best precautions individuals can take are the same as always: Use repellants, use flea and tick control products on your pets, and don’t let water stand around outside your house.