Viral fingerprints
How the genotype of measles can help us dispel some false information
Measles has been spreading for a few months now, leading to the largest number of cases since 2000. Along with measles, false information is also flourishing, which is causing a lot of confusion and harm.
Things are hard right now, so I understand why you might have questions about what is causing the measles outbreak (or maybe you know someone who does). So, you should know that the outbreak is due to measles caught from strains circulating in the wild, not from the vaccine version of measles.
I recently came across multiple accounts on social media trying to blame the MMR vaccine for these measles outbreaks. So today, I want to walk you through one of the simplest reasons why we know that isn’t true – measles genotypes.
What’s a Genotype?
Everything that is living has genetic material that gives the directions to make all of the components it needs to exist. Most living things use DNA as their genetic material, but some viruses, like measles, use RNA instead.
It doesn’t matter if it's DNA or RNA, in both cases the directions are made up of four types of building blocks, called nucleotides. It’s the order of these nucleotides that gives the directions and dictates the end product, we call this order the “genotype”.
We can look at the specific order of nucleotides to identify living things. This is one way people can tell one person's DNA from another, and how we can tell viruses apart. It can even tell two different strains of the same virus apart. You can think of it like unique fingerprints.
There are many different genotypes of measles circulating in the wild. By identifying the genotype of a measles virus found in a sick person, scientists can trace where the virus likely started and whether it matches strains circulating locally or in other areas.
What About the Vaccine?
The measles vaccine uses a weakened form of the measles virus. This means the virus is alive, but it’s been adapted so it cannot cause measles in healthy people (more on this here). The vaccine strain belongs to the measles genotype A.
Genotype A has not been found circulating in the wild for years. Furthermore, there has never been documented transmission of the vaccine strain of measles. And remember, we CAN know this for sure by looking at the genotype.
So what genotype is causing the current outbreak?
The measles strain spreading in this outbreak belongs to the wild circulating genotypes. Specifically, the samples tested in Texas (at least 208) have been caused by the D8 genotype. This genotype is distinct from and NOT found in the measles vaccine.
This means the measles outbreak is being caused by imported wild-type measles viruses. When a case is imported to an area with low vaccine coverage it can spread rapidly because of how contagious measles is.
The Take Home
The vaccine version and the outbreak version of measles are not the same genotype. But yes, the vaccine still works for all the wild type strains! The measles outbreak is being caused by imported wild-type measles virus and low vaccine coverage. Vaccination remains our best protection from measles and all of its complications.
If you have more questions about measles, vaccines, or other science topics please hit reply or comment below. I’d love to know what to focus on for future posts!
Thanks for being here!
From the Teacher’s House
I just finished reading The Curious Case of Jane O by Karen Thompson Walker. She is one of my favorite authors and this book had me hooked from the beginning. I highly recommend!
We recently got back from a trip to CT to see my best friend and her family. I still had to do some work while away, but it was a delightful trip that reminded me of all of the reasons it is so important to keep trying to make the world a better place. See our four kids together melted my heart in the best way.
I am so enjoying running outside now that the weather is better. It does wonder for my stress and mood. I am trying to decide what half marathon to sign up for — any New England suggestions for me?
My friend
recently helped me alter my mindset a bit. I’ve been saying “it’s a marathon not a sprint” related to all the work that needs to happen right now. But she reframed it as “a relay” recently and reminded her followers that we can pass the baton to others and take a break when needed. This was really important for me to hear. So this is your reminder — we are in a relay! Pass the baton and take breaks as needed.
My science posts will always be free, but if you find my work valuable and want to support it you can upgrade to a paid subscription! I appreciate everyone for being here regardless. <3
Great post! Love the relay/marathon message too. That's a good thing to remember.