United States Measles Case Fatality Rate

Key Points:

• Case Fatality Rate for Measles in the USA is 1-3 deaths per 1,000 cases
• This rate is based on USA measles figures, not global figures

There's an article on VaxTruth, 'Measles at Disneyland!' about the measles cases traced back to Disneyland the 2012 Indiana outbreak. It's a behemoth post so I can completely understand the author not wanting to "reinvent the wheel" by writing something new for the Disneyland cases. Personally I'm not a fan of such massive articles, preferring smaller more specific posts instead as I think they tend to be a bit more constructive. So that's exactly what I'm going to do, I'm going to look into the alleged problems with the case fatality rate (CFR) provided by the CDC.

From the VaxTruth article:

The statement that 1 out of 1,000 “children” who get measles will die from it is misleading. That’s because those numbers are based on the global measles problem; not measles in the United States.

When I wrote the article on the Indiana “outbreak” in 2012, there was a CDC MMWR publication I used and linked to, to show how inflated the 1/1000 number was. That publication has either been moved or taken down. I will try to find it and include it here, but for now I have to leave this information without the citation (due to limited time). In the CDC’s MMWR report on measles, it stated there are approximately 20 Million cases of measles each year worldwide and of those cases, there are approximately 197,000 deaths. This appears to be where they are getting their figure of 1 or 2 deaths per 1,000 cases.  The MMWR report also stated that about 1/2 of the deaths from measles occur in India.  So if half of the roughly 200,000 deaths from measles occurs in India, then the rest of the world splits the remaining 100,000 deaths per year. That still sounds like a lot. And SOME of them were children – not all. So the 1 in 1,000 deaths among children statement just doesn’t make sense, unless you are talking about children in third-world countries.

Before I get into the case fatality rate I'll just clear up the "missing MMWR report". Looking at the original article from 2012, the figures don't come from an MMWR but from the CDC's old overview page for measles. I'm not sure why there's any confusion about it considering she still has the link in the original article.

There's a couple of changes from the 2012 version to the present form of the article. Most noticeable of all, the author is now more definite about where the figures comes from: "...those numbers are based on the global measles problem...".

There doesn't appear to be any reason for such confidence.

The author didn't seem to have bothered trying to find the source of the case fatality rate provided by the CDC, instead they made an assumption based on a mathematical error.

(197,000 deaths ÷ 20,000,000 cases) × 1,000 = 9.85 deaths per 1,000 cases

Unless a person thinks that 200,000 divided by 20 million is 1/1,000 there is no reason to think the case fatality rate used by the CDC is based on the global figures listed in the overview.

The overview page is intended as a bit of light reading so it doesn't delve into its sources. For a more complete look at vaccine-preventable diseases on the CDC site, a good place to start is the pink book. Looking at the complications section in the measles chapter, the case fatality rate is given as approximately 2 deaths per 1,000 cases and this is based on "the cases in the United States from 1985 through 1992."

Alternatively, by searching pubmed for the measles case fatality rate in the USA, one of the earliest results found is this paper which gives a case fatality rate of 3 deaths per 1,000 cases based on measles cases in the USA from 1987 to 2000.

It didn't require much effort to confirm that the case fatality rate provided by the CDC was indeed based on measles in the USA and not on global information. It's unfortunate that the author at VaxTruth didn't appear to put in any effort to confirm it herself.

UPDATE: Added key points to the top of the post. (Mar 5th, 2015)

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