CDC says mosquito, tick infections spiking

The number of people who get diseases transmitted by mosquito, tick and flea bites has more than tripled in the United States in recent years, federal health officials reported Tuesday. Since 2004, at least nine such diseases have been newly discovered or introduced into the United States.

Warmer weather is an important cause of the surge in cases reported to the Centers for Disease Control and Prevention, according to the lead author of a study in the agency’s Morbidity and Mortality Weekly Report.

But the author, Dr. Lyle R. Petersen, the agency’s director of vector-borne diseases, declined to connect the increase to the politically fraught issue of climate change. Many other factors are at work, he emphasized, while noting that “the numbers on some of these diseases have gone to astronomical levels.”

Between 2004 and 2016, about 643,000 cases of 16 insect-borne illnesses were reported to the CDC — 27,000 a year in 2004, rising to 96,000 by 2016. (The year 2004 was chosen as a baseline because the agency began requiring more detailed reporting then.) The real case numbers were undoubtedly far larger, Petersen said.

The study did not delve into the reasons for the increase, but Petersen said it was probably caused by many factors, including two related to weather: Ticks thriving in regions previously too cold for them, and hot spells triggering outbreaks of mosquito-borne diseases. Other factors, he said, include expanded human travel, suburban reforestation and a dearth of new vaccines to stop outbreaks.

CDC officials called for more support for state and local health departments.