Wednesday, January 28, 2015

Disneyland Measles Outbreak is Due to Measles

The current measles outbreak primarily emanating from Disneyland in California is up to 100 cases but not all are epidemiologically-linked to the Disneyland outbreak.  As is usual with measles outbreaks, most were completely unvaccinated, some were too young to be vaccinated.  There are numerous articles highlighting this well-known fact and that has anti-vaxxers on the defensive.  In fact, this screed by Laura Hayes appeared on the anti-vaxx, autism-hating blog Age of Autism:
1.  Has there been any laboratory confirmation of even one case of the supposed measles related to Disneyland?  If yes, was the confirmed case tested to determine whether it was wild-type measles or vaccine-strain measles?  If not, why not?  These are important questions to ask. Is it measles or not? If yes, what kind, because if it's vaccine-strain measles, then that means it is the vaccinated who are contagious and spreading measles resulting in what the media likes to label "outbreaks" to create panic (strange how they've completely missed the Autism outbreak going on for the past 25 years). It would be what one might call vaccine fallout.  People who receive live-virus vaccines, such as the MMR, can then shed that live virus, for up to many weeks...and can infect others.  Multiply that in your head by all of the people who receive not only the MMR live-virus vaccine, but many others. Other live-virus vaccines include the nasal flu vaccine, shingles vaccine rotavirus vaccine, chicken pox vaccine, and yellow fever vaccine.
That's right, apparently Laura Hayes is really good at asking the really dumb questions but not too adept at finding the answer before postulating what measles strain is circulating amongst those infected.  Hint: it isn't the vaccine strain.  This wasn't hard to find and is very specific about the genotypes:
Measles genotype information was available from 9 measles cases; all were genotype B3 and all sequences linked to this outbreak are identical. The sequences are also identical to the genotype B3 virus that caused a large outbreak in the Philippines in 2014. During the last 6 months, identical genotype B3 viruses were also detected in at least 14 countries and at least 6 U.S. states, not including those linked to the current outbreak.
And even more information regarding the differences in wild-type strains and vaccine-strains can be found here:

Genetic Characterization and Sequencing

Wild-type measles viruses have been divided into distinct genetic groups, referred to as genotypes, based on the nucleotide sequences of their hemagglutinin (H) and nucleoprotein (N) genes, which are the most variable genes on the viral genome.
The 450 nucleotides encoding the carboxy-terminal 150 amino acids of the nucleoprotein has up to 12% nucleotide variation between genotypes. The 450 nucleotides that encode the carboxy-terminal region of the nucleoprotein (N–450) are required for determination of the genotype. The measles genotyping protocol is available from CDC.
For each genotype, a reference strain is designated for use in genetic analysis (phylogenetic analysis), usually the earliest known virus isolation of that group. The means of referring to the genotypes has been standardized using alphabetical designations for the main groupings (clades). Within the main clades, numerals are added to identify the individual genotypes.
The following 19 genotypes have been detected since 1990:
A*, B2, B3, C1, C2, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, G2, G3, H1, H2
*Vaccine strains Moraten, Edmonston, Zagreb are all genotype A.
 There were 2 putative wild-type cases of measles identified as genotype A in 2008.
During 2011, 8 genotypes were identified by global surveillance:
B2, B3, D4, D8, D9, D11, G3, H1
Gosh that was simple.  Laura Hayes asks a lot more dumb questions and fills in the answers with her own fact-free assertions but there is too much stupid and not enough time to take them apart.  The important point here is that measles outbreaks are caused by measles viruses (not vaccine-strain) and a critical mass of anti-vaxxers clustering and causing large gaps in herd immunity.