No sooner do we close the books on one of the worst flu seasons in recent history than the Centers for Disease Control and Prevention tells us to expect a high volume of tick-, mosquito-, and flea-borne infections as the weather warms up. It’s not just greater numbers of the same diagnoses, either; new tickborne diseases like Heartland virus are showing up in the continental U.S. Tickborne diseases are climbing most in the Northeast, Upper Midwest, and California. Most mosquito-related outbreaks (eg, Zika virus) have occurred in Puerto Rico, the Virgin Islands, and American Samoa; one exception is West Nile virus, which now appears unpredictably across the country. The only flea-borne disease called out by the CDC is plague, which it called “rare but persistent.” Between two and 17 cases were reported from 2004 to 2016, mostly in the Southwest. Overall, the number of people getting diseases transmitted by mosquito, tick, and flea bites has more than tripled in the U.S. in recent years. Between 2004 and 2016, about 643,000 cases of 16 insect-borne illnesses were reported to the CDC. In 2004 there were 27,000; by 2016 that number was 96,000 cases.