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In order for this to occur, there needs to be a selection pressure. It doesn't just magically happen. The virus behind Marek's disease in chickens hasn't gotte
by foobiekr 5y ago
In order for this to occur, there needs to be a selection pressure. It doesn't just magically happen.
The virus behind Marek's disease in chickens hasn't gotten less severe over time, it's gotten much, much more severe, as an example. HIV does not seem to have gotten less severe, nor smallpox.
- mariodiana 5y agoThe virus behind Marek's disease in chickens got much more severe because of the leaky vaccine used on chickens. Here's some introductory material: https://www.pbs.org/newshour/science/tthis-chicken-vaccine-makes-virus-dangerous https://www.nationalgeographic.com/science/article/leaky-vaccines-enhance-spread-of-deadlier-chicken-viruses https://www.youtube.com/watch?v=haRMKsI-jKY And here are a couple of papers: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002198 https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002236
- foobiekr 5y agoYes, Marek's is actually a good illustration of how diseases can go in the other direction.