Claims of Warming-Aided Vectorborne Diseases: a Follow-up

Guest Essay by Kip Hansen

Last week I wrote about the latest CDC report on the increased incidence of vectorborne diseases in the United States.  The report was misrepresented by the magazine Science News whose report depended entirely on an article in the New York Times titled: “Tick and Mosquito Infections Spreading Rapidly, C.D.C. Finds”.    The Science News piece echoed the New York Times’ journalist  Donald G. McNeil Jr.’s  claim that “Warmer weather is a major cause for the explosion in these vector-transmitted diseases, The New York Times reports, as ticks thrive in areas once too cold, and mosquito populations mushroom during heat waves.” (the link to the NY Times article is original in the Science News piece.)

The actual claim made in the NY Times was this:

“Warmer weather is an important cause of the surge, according to the lead author of a study published in the C.D.C.’s Morbidity and Mortality Weekly Report.”

Sharp eyes and critical minds can see already that the original NY Times’ claim of warmer weather being an “important cause” has been elevated by Science News  to be a “major cause” and the NY Times’ “surge” has been magnified into “the explosion”.

I reported here that the CDC research report under question does not contain the words “warming” or “warmer” or “weather”,  nor does it contain the words “climate” or “climate change”.  The official spin-off factsheets and public information materials also contain no mention whatever of global warming, warmer weather, or climate change.

Having used a certain journalists’ trick myself many times, I suspected the McNeil of the Times had done the same, but with a particularly (in my opinion) unethical twist.  The problem is that the CDC report does not blame global warming for the increased incidence and geographical spread of mosquito- and tick-borne diseases, yet the Times (McNeil) wants to say that.  McNeil then either telephones or emails one of the authors of the report, asks some leading questions, and turns the answer(s)  into  this  “crypto-quote” — “Warmer weather is an important cause of the surge, according to the lead author….”.  The crypto-quote gets picked up by Science News and is magnified into “Warmer weather is a major cause….”.

CRYPTO_QUOTE:  an attributed statement that is not a direct quote but rather a paraphrased statement, often derived from the answer to one or more undisclosed questions.  Crypto-quotes are nearly impossible to refute as the question(s) used to elicit the response is withheld along with the actual words used in that response.  A crypto-quote is then simply a journalist’s interpretation of an unknown response to an unknown question.

My question in all of this was:

“How did this misunderstanding come about [?]– two major news sources, one an “international newspaper of record” and one a sub-set of one of the world’s leading science journals have both claimed that your team identified “warmer weather” as a major cause of “the explosion in these vector-transmitted diseases.   I am hoping for a clarifying statement that I can quote.”

I posed this exact question to Dr. Ron Rosenberg, Division of Vector-Borne Diseases/CDC, who was listed in the study as the Corresponding Author and is the Associate Director for Science at CDC’s Division of Vector-borne Diseases.

Here is his reply:

“Thanks for calling this to my attention. I haven’t read or heard any of Dr Petersen’s interviews as division director so it would be best if you seek clarification from him; I’m copying some CDC people who should be able to arrange that. 

You are correct that the MMWR article did not mention any specific role for climate in the increase in cases. Doubtless changes in climate affect transmission but the relation is complex and not well understood. For example, while Lyme cases seem to be increasingly reported from farther north over the last decade, they’ve been moving west and southward as well.”

[Lyme cases could not move further east from their origin — Connecticut/Rhode Island —  as that way lies the Atlantic Ocean.]

True to his word,  Dr. Rosenberg cc’d his response to several colleagues at CDC, including Kate Fowlie,  CDC Press Officer, who offered this additional response:

Thank you for reaching out.

Dr. Petersen has said that the increase in diseases caused by the bite of an infected mosquito, tick, or flea in the U.S. is likely due to many factors, and changes in temperature is likely one of them. 

Other factors include:

• Spread of pathogens

Mosquitoes and ticks and the germs they spread are increasing in number and moving into new areas. Infected animals can also contribute to spread of pathogens into new areas.

• Travel and commerce

Overseas travel and commerce are more common than ever before. A traveler can be infected with a mosquito-borne disease, like Zika, in one country, and then unknowingly transport it home.

• Newly identified or newly introduced pathogens

Finally, new germs spread by mosquito and tick bites have been discovered and the list of nationally notifiable diseases has grown.

• People’s behavior

People are outside more often in warmer weather and are more likely to get bitten.

Dr. Petersen spoke at the telebriefing last week and the transcript is available online here:

https://www.cdc.gov/media/releases/2018/t0501-vs-vector-borne.html

In Kate Fowlie’s follow-on email, we finally see the “warmer weather smoking gun”  — the CDC says officially (note that Kate is copy-and-pasting from the Factsheet)  “People are outside more often in warmer weather and are more likely to get bitten.”

As suspected, this innocent obviously-true little tidbit has been spun and magnified first into an “important” cause and then re-magnified into a “major” cause of the increase and spread of vectorborne diseases.   The CDC’s  warmer weather means just what it does to you and I — when the weather is nice, we tend to go out — many of us to local parks and woods  and many more of us into our yards — where we are more likely to encounter biting mosquitoes and nasty little ticks.

For those with a real interest in vectorborne diseases and what the CDC had to say about them, I recommend reading the transcript of the CDC’s telebriefing of the media on the topic.

There are, of course, many ways in which temperature differences affect biological vectors (mosquitoes, ticks, fleas), disease transmission and geographical spread of these diseases — for instance, high temperatures can cause mosquitoes to mature faster and cause infected mosquitoes to become ‘more’ infectious.  As Dr. Rosenberg correctly points out, ”the relation is complex and not well understood”.

Ron Bailey, at Reason.com, covered this story from a slightly different viewpoint in his blog post “Over-Regulation Is Making Us More Vulnerable to Disease”.  (h/t Roger Knights).

Late addition:  9 May 2018 2200 hrs Eastern Time

A dated but well-rounded view of this topic can be found in this paper from 2001:

Climate Change and Mosquito-Borne Disease

by Paul Reiter — Dengue Branch, Division of Vector-Borne Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, San Juan, Puerto Rico

The paper begins with this:

“The earth’s climate has always been in a state of change. For nearly three centuries it has been in a warming phase. This was preceded by a cold period, the Little Ice Age, which was itself preceded by a warmer phase known as the Medieval Warm Period, or Little Climatic Optimum. Such changes are entirely natural, but there is evidence that in recent years a portion of the current warming may be attributable to human activities, particularly the burning of fossil fuels. The potential impact of this global warming on human health is a major subject of debate.”

and ends with this:

“Final Comment

The natural history of mosquito-borne diseases is complex, and the interplay of climate, ecology, vector biology, and many other factors defies simplistic analysis. The recent resurgence of many of these diseases is a major cause for concern, but it is facile to attribute this resurgence to climate change. The principal determinants are politics, economics, and human activities. A creative and organized application of resources is urgently required to control these diseases regardless of future climate change.”

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Author’s Comment Policy:

The use of what-I-have-dubbed crypto-quotes has led to a lot of flawed news and is a feature of lousy journalism.   It is one thing to honestly summarize a speech into a few lines of journalism, as long as the original speech is available and linked.  It is another thing entirely to paraphrase a response to an unrevealed question in a way that puts words not spoken into the mouths of others.  The later is simply unethical.

This essay is about Science Journalism — not climate change or mosquitoes.

[Just in case: it is not about coyotes either!]

Always happy to read and respond to your comments here or you can email me at my first name at the domain i4 decimal net.

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