3 ms·

Not true I'm afraid. Of course, if a virus killed you before you had a chance to pass it on then yes - but most viruses (including SARS-CoV-2) kill you slowly

Not true I'm afraid. Of course, if a virus killed you before you had a chance to pass it on then yes - but most viruses (including SARS-CoV-2) kill you slowly enough to have plenty of opportunity to propagate, there is no selection pressure to be less deadly. To my knowledge, we have no evidence that any human virus has evolved to become less virulent (please furnish examples if I'm wrong!). Unfortunately this common myth, that contagiousness is inversely correlated with lethality, has been used by those who would wish to downplay this public health disaster for whatever reason.

semerda 5y ago
Replication-incompetent adenoviral vectors? Lex Fridman had a virologist on his podcast talking about the mutations done to the adenovirus to make it safe for the delivery of the s-protein (used in viral vector J&J + AstraZ vax). Maybe I misunderstood that?
- somewhereoutth 5y ago
  Engineered vs evolved. For sure you can take a virus and knock out the bad bits - but I believe we have no evidence this has occurred in the wild due to selection pressure.
  - semerda 5y ago
    I’m not talking about inactivation with formaldehyde. If they did that in the viral vector it would disable the delivery mechanism (adenovirus).
janmo 5y ago
I guess the Spanish flue probably did
danenania 5y ago
“To my knowledge, we have no evidence that any human virus has evolved to become less virulent (please furnish examples if I'm wrong!).” Isn’t this what happened with the influenza strain that caused the Spanish Flu pandemic?
- somewhereoutth 5y ago
  My understanding is that in fact we don't know. A likely explanation for its disappearance is that it ran out of susceptible hosts. Specifically, we have no evidence of a successor virus that was both less lethal, and induced immunity to the original.
adolph 5y ago
I looked up Ebola to see if it has changed over time [0] and it looks like nada, since outbreaks are generally zoonotic, which means that the viral mutation-selection happens outside humans. Of note is Ebola's relation to Marburg, which was imported to Europe with Uganda-sourced lab monkeys. Two large outbreaks that occurred simultaneously in Marburg and Frankfurt in Germany, and in Belgrade, Serbia, in 1967, led to the initial recognition of the disease. The outbreak was associated with laboratory work using African green monkeys (Cercopithecus aethiops) imported from Uganda. Subsequently, outbreaks and sporadic cases have been reported in Angola, the Democratic Republic of the Congo, Kenya, South Africa (in a person with recent travel history to Zimbabwe) and Uganda. In 2008, two independent cases were reported in travellers who had visited a cave inhabited by Rousettus bat colonies in Uganda. [1] 0. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4642951/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4642951/ 1. https://www.who.int/news-room/fact-sheets/detail/marburg-virus-disease https://www.who.int/news-room/fact-sheets/detail/marburg-vir...

semerda 5y ago

Replication-incompetent adenoviral vectors? Lex Fridman had a virologist on his podcast talking about the mutations done to the adenovirus to make it safe for the delivery of the s-protein (used in viral vector J&J + AstraZ vax). Maybe I misunderstood that?

somewhereoutth 5y ago
Engineered vs evolved. For sure you can take a virus and knock out the bad bits - but I believe we have no evidence this has occurred in the wild due to selection pressure.
- semerda 5y ago
  I’m not talking about inactivation with formaldehyde. If they did that in the viral vector it would disable the delivery mechanism (adenovirus).

janmo 5y ago

I guess the Spanish flue probably did

danenania 5y ago

“To my knowledge, we have no evidence that any human virus has evolved to become less virulent (please furnish examples if I'm wrong!).” Isn’t this what happened with the influenza strain that caused the Spanish Flu pandemic?

somewhereoutth 5y ago
My understanding is that in fact we don't know. A likely explanation for its disappearance is that it ran out of susceptible hosts. Specifically, we have no evidence of a successor virus that was both less lethal, and induced immunity to the original.

adolph 5y ago

I looked up Ebola to see if it has changed over time [0] and it looks like nada, since outbreaks are generally zoonotic, which means that the viral mutation-selection happens outside humans. Of note is Ebola's relation to Marburg, which was imported to Europe with Uganda-sourced lab monkeys. Two large outbreaks that occurred simultaneously in Marburg and Frankfurt in Germany, and in Belgrade, Serbia, in 1967, led to the initial recognition of the disease. The outbreak was associated with laboratory work using African green monkeys (Cercopithecus aethiops) imported from Uganda. Subsequently, outbreaks and sporadic cases have been reported in Angola, the Democratic Republic of the Congo, Kenya, South Africa (in a person with recent travel history to Zimbabwe) and Uganda. In 2008, two independent cases were reported in travellers who had visited a cave inhabited by Rousettus bat colonies in Uganda. [1] 0. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4642951/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4642951/ 1. https://www.who.int/news-room/fact-sheets/detail/marburg-virus-disease https://www.who.int/news-room/fact-sheets/detail/marburg-vir...