Scientists have warned us for a long time that invasive species and tropical diseases will thrive and spread in a changing and warming climate. And until recently, even the U.S. Centers for Disease Control and Prevention (CDC) was very blunt that climate change was driving an increase in insect-borne diseases.

But the Trump administration has been censoring and deleting references to climate change by federal scientists, websites, and agencies since its inception. And that seems to extend to the CDC as well, even when it is discussing one of the fastest growing threats to Americans’ health.

The CDC reported Tuesday that the number of Americans catching diseases from mosquito, flea, and tick bites more than tripled in the past decade. Its latest “Vital Signs” report explains that reported cases of insect-borne disease like dengue, Zika, and Lyme have soared from 27,000 in 2004 to 96,000 in 2016.

Worse, as the CDC explains, “The reported data substantially underestimate disease occurrence,” since many cases go unreported or misdiagnosed.

Thanks in part to warming temperatures, reported U.S. cases of insect-borne diseases have more than tripled in the past decade. CREDIT: CDC

But the report fails to mention climate change or warming temperatures as having anything to do with this increase.

Significantly, though, its author, Dr. Lyle R. Petersen, the CDC’s director of vector-borne diseases, made clear during a press call and media interviews that warming temperatures and shorter winters have allowed ticks to invade areas that had been too cold for them and that heat waves are a major cause of mosquito borne disease outbreaks. Petersen explained that many factors, such as increased travel, have also aided the spread of the disease.


“We know temperature is very important,” said Petersen. “If you increase temperature, in general tick populations can move further north and extend their range.” Also, “when the tick season is longer, people are exposed over longer periods.” Lyme, which accounts for some four fifths of tick-borne disease, has doubled in the past decade.

As for mosquitoes, Petersen explained that as the temperature rises, “The amount of virus in the mosquito increases, and when it bites you, more virus gets into you and the chances of you getting infected and becoming sick goes up.”

Yet, even though Petersen himself explained in detail why warming temperatures are a major factor in the spread of insect-borne diseases, neither the CDC report nor its four-page summary document, nor the report’s website make any mention whatsoever of this point. Nor do they make any mention of climate change.

Mashable noted that during the press call, Petersen “declined to answer whether or not human-caused global warming was responsible for these temperature increases.” He said that’s a question better left “for meteorologists.”


The CDC was not always so reluctant to attribute the rise in insect-borne diseases directly to climate change. You can still find pages created before the Trump administration that fully report the science, such as a two-pager titled, “Climate change increases the number and geographic range of disease-carrying insects and ticks.”

There’s no ambiguity in that document, but then again, the page that link is on, “Climate Effects on Health,” was lasted updated in July 2016.