Connect Pests and Pest-Borne Diseases to the Climate Crisis This Summer

This summer, we urge you to report and comment accurately on pests and pest-borne diseases by making clear that they are connected to the climate crisis. In 2018, outlets too rarely made this connection, leaving their audiences without critical information—the root causes of, and solutions to, the very problems being discussed.

Pests and the diseases they spread are on the rise due to higher temperatures and other climate disruptions caused by greenhouse gas pollution, putting humans at greater risk of bites and serious illnesses. Ticks and mosquitoes are common vectors. In the U.S., mosquito season has begun, and tick season is in full swing.

Much of the connection between pests, pest-borne illnesses, and climate disruption is straightforward: Warmer temperatures extend the range of disease-carrying insects and give them longer active seasons. Increases in rainfall, humidity, and flooding can increase breeding areas for disease vectors (particularly mosquitoes), and offspring hatch faster in warmer temperatures.

We analyzed 2018 coverage of pests and pest-borne illnesses by national television news networks, top newspapers, and top digital media and found that, although outlets generally showed improvement over 2017, they still too rarely connected climate-relevant topics to the climate crisis:

Growing mosquito populations. Only 25% of television transcripts, 22% of online news articles, and 13% of print media pieces that discussed growing mosquito populations also mentioned climate change. In 2017, 3% of television transcripts, 18% of online and 8% of print news articles made the connection.

Growing tick populations. The numbers were lower for ticks: Only 18% of television transcripts, 10% of online news articles, and 9% of print pieces discussing increasing tick populations also mentioned climate change. In 2017, the figures were 9% for transcripts, 8% for online news articles, 5% for newspaper articles.

The spread of Lyme disease. Among pieces on the spread of Lyme disease, 29% of television transcripts, 27% of print articles, and 45% of online news articles also mentioned climate change. The percentage of print articles mentioning climate did not change from 2017 to 2018. The rate for digital pieces was 32% in 2017. And no television segment on the spread of Lyme disease mentioned climate change in 2017.

The spread of West Nile virus. Regarding the spread of West Nile virus, 12% of print news articles mentioned climate change. That rate is lower than 2017, when 14% of pieces did so. Digital news sources improved slightly, from 27% in 2017 to 31% in 2018. Television news networks essentially did not cover the spread of West Nile virus; it was mentioned not once in 2018 and just once in 2017.

The spread of Zika virus. For coverage of the spread of Zika virus in 2018, 19% of print articles and 26% of online news articles also mentioned climate change. These are improvements over 2017, when only 8% of print articles and 14% of transcripts and online news pieces did so. In 2018, 3 of 5 television news segments linked the growth of Zika to climate change, compared to 3 of 21 in 2017.

Table 2 provides more detailed data on mentions of pests, and pest-borne illness, and climate change.

For producers, editors, or reporters who want to know whether or how to discuss climate change in the context of phenomena like rising pest populations or extreme weather, there are excellent guides. Major examples are Climate Central, in particular its Climate Matters program, and Climate Nexus, including its Climate Signals project.

In addition, newsrooms that want to provide better climate reporting but lack the resources to do so can adapt or reprint stories from other publications or wire services, some of which are producing a good deal of excellent work. Standouts include The New York Times, The Washington Post, and the Associated Press.



For this analysis, we searched television news transcripts, print newspaper articles, and online news articles on relevant topics—for example, “Lyme disease” or “Zika” near “spread”—to find the number of pieces on each topic that mentioned and did not mention climate change. The terms we used are listed in Table 1 at the end of this report. We counted a piece as discussing a topic if it made the barest mention of the relevant terms—that is, if the piece merely turned up in the search results for those terms. Throughout this report, we use “piece” and “article” interchangeably to refer to all materials covered by this analysis: reported articles, opinion columns, editorials, and transcripts of television broadcasts.

For print articles, we searched the top 50 U.S. papers by circulation. The list of these papers was compiled using data from Cision in May 2018 and is limited to English-language, subscription newspapers.* Many significant local dailies are not included, such as The Palm Beach Post and The Charlotte Observer. The same is true of papers that cover Capitol Hill, like The Hill, Politico, and Roll Call, although the list of digital media includes This analysis also does not include radio or local television.

We used Nexis to search the top 50 U.S. newspapers and television transcripts from six national television news networks (ABC, CBS, CNN, Fox, MSNBC, and NBC). We used the “Group Duplicates” feature, set on “High Similarity.” We did not examine the results to discard false positives.

For online sources, we used Media Cloud’s “U.S. Top Online News 2017” collection, which includes 32 sources.** Media Cloud does not permit proximity searches, in which one searches for two terms within a certain number of words of one another, or in the same sentence or paragraph. Therefore, in instances where we used proximity searches for television transcripts and newspapers, we were limited to using the AND connector for digital content. As a result, some searches of digital sources are significantly more inclusive than those for newspapers and television.

* The newspapers are The Arizona Republic, the Arkansas Democrat‐Gazette, the Atlanta Journal‐Constitution, The Baltimore Sun, The Boston Globe, The Buffalo News, the Chicago Sun‐Times, the Chicago Tribune, The Cincinnati Enquirer, The Plain Dealer (Cleveland), The Columbus Dispatch, the Dallas Morning News, The Denver Post, the Detroit Free Press, the East Bay Times, the Honolulu Star‐Advertiser, the Houston Chronicle, the Indianapolis Star, the Kansas City Star, the Las Vegas Review‐Journal, the Los Angeles Times, The Mercury News, the Miami Herald, the Milwaukee Journal Sentinel, the Daily News (New York), the New York Post, The New York Times, Newsday, The Oklahoman, the Omaha World‐Herald, The Orange County Register, The Oregonian, the Orlando Sentinel, the Philadelphia Inquirer, the Pittsburgh Post‐Gazette, The Sacramento Bee, The San Diego Union‐Tribune, the San Francisco Chronicle, The Seattle Times, the St. Louis Post‐Dispatch, the St. Paul Pioneer Press, the Star Tribune, The Star‐Ledger, the Sun Sentinel, the Tampa Bay Times, The Times Picayune, USA Today, The Virginian‐Pilot, The Wall Street Journal, and The Washington Post.

** According to Media Cloud, the collection includes the “top news websites of the year by August 2017 in the United States, according to data from comScore, Activate and Alexa.” The websites are:, Breitbart, Business Insider, Buzzfeed, CBS News, CNBC, CNN, Daily Caller, Daily News, Forbes, FOX News, Guardian – United States, Huffington Post, LA Times, NBC News, New York Times, New Yorker, NewsMax, Politico, Reuters,, The Atlantic, The Blaze, Time, USA Today, Vox, Wall Street Journal, Washington Post, and Yahoo News – Latest News & Headlines. Media Cloud lists three additional websites in the collection (Bloomberg, Drudge Report, and for a total of 32, but it does not appear to have any content from these three sites for the period covered by this analysis.


Table 1. Search Terms

Topic Search Terms*
Lyme disease “lyme disease”
Lyme disease spreading ((“lyme disease” /s growing) OR (“lyme disease” /s spreading) OR (“lyme disease” /s rising))
Ticks ((tick* /s growing) OR (tick* /s rising) OR (tick* /s population) OR (tick* /s spread))
Mosquitoes ((mosquito* /s growing) OR (mosquito* /s rising) OR (mosquito* /s population) OR (mosquito* /s spread))
West Nile virus “west nile virus”
West Nile spreading ((“west nile virus” /s growing) OR (“west nile virus” /s rising) OR (“west nile virus” /s population) OR (“west nile virus” /s spread))
Zika zika
Zika spreading ((zika /s growing) OR (zika /s rising) OR (zika /s population) OR (zika /s spread))

* For Media Cloud, we used “AND” instead of proximity connectors such as “/3” or “/s”

Table 2. Mentions of pests and pest-borne illnesses by the top 50 U.S. newspapers by circulation and six national television news networks, 2018

Topic Sources 2018 2017
Mentioned Climate Total Percentage Mentioned Climate Total Percentage
Growing Mosquito Population All Sources 193 1,030 18.7% 229 1,605 14.3%
Newspapers 50 379 13.2% 48 573 8.4%
Television 5 20 25.0% 1 30 3.3%
Online News 138 631 21.9% 180 1,002 18.0%
Growing Tick Population All Sources 148 1,489 9.9% 100 1,511 6.6%
Newspapers 56 618 9.1% 31 658 4.7%
Television 11 60 18.3% 4 43 9.3%
Online News 81 811 10.0% 65 810 8.0%
Lyme Disease Growing or Spreading All Sources 67 184 36.4% 52 178 29.2%
Newspapers 22 82 26.8% 17 63 27.0%
Television 2 7 28.6% 0 6 0.0%
Online News 43 95 45.3% 35 109 32.1%
Lyme Disease All Sources 125 755 16.6% 96 872 11.0%
Newspapers 46 410 11.2% 30 439 6.8%
Television 12 31 38.7% 0 35 0.0%
Online News 67 314 21.3% 66 398 16.6%
West Nile Virus Growing or Spreading All Sources 41 195 21.0% 32 140 22.9%
Newspapers 12 100 12.0% 7 49 14.3%
Television 0 0 n/a 1 1 100.0%
Online News 29 95 30.5% 24 90 26.7%
West Nile Virus All Sources 66 509 13.0% 44 381 11.5%
Newspapers 28 348 8.0% 17 245 6.9%
Television 3 6 50.0% 1 7 14.3%
Online News 35 155 22.6% 26 129 20.2%
Zika Virus Growing or Spreading All Sources 112 463 24.2% 217 2,029 10.7%
Newspapers 27 139 19.4% 98 1,183 8.3%
Television 3 5 60.0% 3 21 14.3%
Online News 82 319 25.7% 116 825 14.1%
Zika Virus All Sources 177 1,082 16.4% 278 2,918 9.5%
Newspapers 59 447 13.2% 98 1,183 8.3%
Television 22 46 47.8% 9 88 10.2%
Online News 96 589 16.3% 171 1,647 10.4%