In the United States, diseases spread by mosquito, flea and tick bites tripled from 2004 to 2016, federal health officials say in a new report. During that time, there were more than 640,000 cases of vector-borne diseases.

“People really do need to take this seriously,” says Dr. Lyle Petersen, the director of the Division of Vector-Borne Diseases in the National Center for Emerging and Zoonotic Infectious Diseases at the Centers for Disease Control and Prevention (CDC).

The new study—published in the CDC’s Morbidity and Mortality Weekly Report—marks the first time the agency has collectively examined the trends for diseases that are spread by pests. The goal, says Petersen, is to gain a better understanding of the growing burden of these illnesses in the U.S., such as Zika, Lyme disease, West Nile virus and more.

The nationwide increase in diseases spread by these insects was largely attributed to mosquitoes and ticks, with ticks being responsible for about 77% of all vector-borne disease reports. The study found that reported tick-borne disease cases doubled during the time period with Lyme disease accounting for 82% of all tick-borne disease reports. Fleas spread disease like the plague, but in far fewer numbers. Overall, from 2004 to 2016, there were nine insect-spread diseases reported for the first time in the United States and U.S. territories, including Zika, chikungunya, Heartland virus, Bourbon virus and more.

MORE: Here’s Everything You Need to Know About Ticks

“The data show that we’re seeing a steady increase and spread of tick-borne diseases, and an accelerating trend of mosquito-borne diseases introduced from other parts of the world,” says Petersen. “We need to support state and local health agencies responsible for detecting and responding to these diseases and controlling the mosquitoes, ticks and fleas that spread them.”

The reason for the increase in diseases spread by mosquitoes largely has to do with the fact that people and goods are traveling and accessing different parts of the world more now than in the past. “All someone needs to do is pick up one of these viruses and fly back to the Untied States,” says Petersen. “If a local mosquito bites them, it can cause an outbreak. That’s what happened with Zika.” Other diseases like West Nile virus can be affected by climate and weather, with warmer weather coinciding with outbreaks.

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The rise in diseases spread by ticks could be partly due to people living in wooded spaces where there are more deer—a popular host for ticks. With less farmland and more suburban living, neighborhoods are developing in places where ticks are common. CDC experts say the geographic range of ticks that spread disease has steadily grown over the past 20 years.

“We desperately need to find new ways to deal with ticks and mosquitoes,” says Petersen. “We need better ways of controlling them and better diagnostic tools.” Petersen says the CDC is helping to provide funding for states to build up their capacity to respond to emerging diseases spread by pests. The agency was recently given a funding increase to $8.3 billion for 2018, including more funding for Petersen’s division.

In the meantime, Petersen recommends that people take precautions — like using repellant, wearing covered clothing and conducting full-body tick checks when necessary — to protect themselves from bites.

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