Monday, October 14, 2019

The CDC is Still Misleading the Public about the Cause of the Respiratory Disease Outbreak: Why?

Last Thursday, CDC finally revised its warning to the public about the vaping-associated respiratory disease outbreak to state clearly that vaping THC-containing products is playing a major role in the outbreak. It stated that: "The latest national and state findings suggest products containing THC, particularly those obtained off the street or from other informal sources (e.g. friends, family members, illicit dealers), are linked to most of the cases and play a major role in the outbreak. Therefore, CDC recommends that you should not use e-cigarette, or vaping, products that contain THC."

In addition, CDC finally recommended that clinicians test case patients for THC with a urine drug screen, something I recommended more than a month ago.

This is a huge step forward because prior to this, the CDC was hiding from the public the fact that THC vaping was playing a major role in the outbreak and failed to provide an explicit warning to stop vaping THC.

The Rest of the Story

However, the very next day, CDC issued the following Tweet:

"CDC and @US_FDA have not identified the cause or causes of lung injuries associated with e-cigarette, or vaping, products. The only commonality among all cases is patients report the use of e-cigarette, or vaping, products."

This is a meaningless statement because in an outbreak investigation, one almost never finds a commonality that ties together every single one of the patients. If you did, you wouldn't need a special CDC team to investigate it. The cause would be quite obvious. In fact, the reason why an epidemiologic investigation is necessary to identify the cause of a disease outbreak is that not all the cases report a common exposure and so special epidemiologic methods are required.

For example, in 2017, CDC investigated an outbreak of Salmonella poisoning in which there were 19 identified cases in seven U.S. states and British Columbia. Many, but not all of the 19 cases reported eating pre-cut coconut pieces from grocery chain A. Specifically, 12 of the 19 cases (63%) reported eating pre-cut coconut pieces from grocery chain A. Records collected at grocery chain A locations and distribution centers uncovered that many of the cases had consumed products from a potentially contaminated lot of pre-cut coconut pieces imported from Indonesia.

The CDC did not tell the public:

"CDC has not identified the cause or causes of grocery A-related Salmonella poisoning. The only commonality among all cases is patients report having shopped at grocery store A. Most of the cases report having eaten pre-cut coconut pieces. However, no single product was common to all of the cases. CDC recommends that people who are concerned about Salmonella poisoning should consider not shopping at grocery chain A."

What did CDC do? They concluded that the pre-cut coconut pieces were the source of the Salmonella outbreak and facilitated a recall of these products. They don't close every one of these stores down completely because they weren't able to find a single product that was common to all of the cases.

Note that unlike youth THC use, there is no stigma associated with eating pre-cut coconut pieces and it is perfectly legal. So even without a good reason for under-reporting, the CDC was still able to identify a common exposure in only 63% of the cases. In fact, they did go back and re-interview some of the patients and in at least one case, they found a store receipt proving that the person had purchased pre-cut coconut pieces even though they had denied it.

If that can happen for pre-cut coconut pieces, then one would certainly expect under-reporting to occur for the use of illegal black market THC vape carts purchased from drug dealers on the street.

I have never before, in any outbreak investigation, heard the CDC withhold a specific warning because not every case reported a common exposure. There is something underneath the surface that is making the CDC reluctant to provide the public with the information and warnings that they need in order to curtail this outbreak.

The rest of the story is that the CDC's communication about the cause of this outbreak has been steadily improving, but we still have a long way to go.

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