Tom writes:

Dear TWIV team,

Thank you for all you do in educating the public – scientists and non-scientists alike.   

I came across an interesting paper – “A common allele of HLA is associated with asymptomatic SARS-CoV-2 infection” after it appeared on a preprint server two years ago.  It was just published in Nature today.  

I am not a scientist. But based on what I have learned from TWiV and other post-COVID acquired knowledge, this seemed a significant discovery as it might explain why some people seem to avoid symptomatic COVID.

My question is, why would it take two years for something like this to get peer reviewed and published?  Is that just the way things go sometimes, even if it is an important discovery?   Or am I overestimating its significance?


Pasadena, CA

Suellen writes:

Hello Vincent and Dickson and the rest of the gang!

Just want to thank you guys and gals for having Dan Wilson on again to “debunk the funk” on RFK Jr.

But I also want to write to warn you all NOT to invite RFK Jr on your show to debate him, because it will only end up badly for you and give him more free publicity.

Since the start of the pandemic, I’ve made the mistake (repeatedly) of engaging anti-maskers and anti-vaxxers in debates, and it’s never turned out well for me — and these people were not even lawyers!

Recently, I was at dinner with a group of colleagues, when one guy announced to the group that there was “irrefutable proof” that “Covid is a bioweapon developed by the Chinese. And the vaccine activated it.”

I sat dumbstruck for a moment, then let him know that I was vaccinated, four times in fact, and that scientists like Eddie Holmes, who were on the front line of the disease when it first emerged, did not believe it came from a lab, and had genetic evidence that it was a zoonotic infection that probably arose in the Huanan Seafood Market.

His reply: “The scientists are being paid to say that. The US government doesn’t want us to know the truth, because they helped China develop the virus. It’s all documented online, by reputable people like RFK, Jr. SARS 1 was their first attempt, and this one is the second. It’s being used to control the population, which is why some ethnic groups are less likely to die.”

Not kidding. He said all that, or something like it.

My final reply: “Ok. Whatever.”

Because there is NO WAY to debunk that funk. When people are that caught up in an irrational story like that, you can’t talk them out of it. And they dismiss any attempts at trying to tell them what’s really true by saying that scientists are being paid off or are part of the “Big Pharma” conspiracy, or part of the Deep State.

This is the same guy who, in 2020, told a group of us that Ivermectin cured Covid. So obviously he’s not going to change and become a rational thinker.

By the way, right after I listened to your podcast, I listened to the latest This American Life with Ira Glass, and you might want to listen to that as well. It’s called “The Florida Experiment” (Episode 805), and it’s all about how Florida is turning into the place the vaccine deniers go to receive support from state government. It’s frightening, really, to hear that they are opening “Medical Freedom Clinics” staffed with physicians who will give out Ivermectin and Hydroxychloroquine, as well as dispense information on the dangers of vaccines. All with the support of Ron DeSantis and his merry band of far-right politicians.

As always, love the podcast. Stay well, my friends, and keep feeding me that wonderful science that I crave!

Your correspondent in Roswell, GA –


Jens (aka Bruce Wayne) writes:

Dear All,

Just piling on my last email with more nitpicky thoughts 😊

You said “Virulence in virology is the capacity of viruses to cause disease” (14:10). I don’t think that’s correct. The capacity of viruses to cause disease is called pathogenicity (from Greek pathos [suffering/disease] and genesis [origin of]). Pathogenicity is a yes/no property, i.e., something either can cause disease or not. That is why saying “highly pathogenic” is wrong and “HPAI” gives me vertigo. Instead, the “degree” of pathogenicity is called virulence, i.e., a more virulent virus causes a more severe disease. And of course an avirulent virus is then per definition necessarily apathogenic. But please fight and educate me on this – this is just how I learned it many moons ago…

Humans and their relatives (17:30). Here is how I understand it:

The closest relatives to humans are other apes. Among those, common chimpanzees (Pan troglodytes (Blumenbach, 1775)) and bonobos (Pan paniscus Schwarz, 1929) are the closest relatives, with about 96% (not 99%) sequence identity: Bonobos Join Chimps as Closest Human Relatives | Science | AAAS; Comparison of human and chimpanzee genomes reveals striking similarities and differences | Broad Institute. The 99(.6)% number comes from the sequences that are shared and therefore comparable but ignore the various DNA insertions and deletions and repeats etc.

This means that the next relatives are gorillas and then the orangutans, and then already quite distantly, gibbons.

Macaques are not apes, but monkeys, which is a further major branch down on the tree, i.e., one should not really say these are “close to humans” (only 93ish%; Analysis of Rhesus Monkey Genome Uncovers Differences with Humans, Chimps | Eberly College of Science ( They are closer to humans than bats and rodents of course. Importantly, this “closer” refers to entire genomes – this does not mean that monkeys are automatically better models for certain human diseases than, say, rats because different biochemical/immunological pathways are differentially conserved across taxa. Gorillas may be very closely related to humans, but if you want to study the effects of meat consumption on human health, gorillas would make terrible models because they are predominantly herbivores…

The preferred vernacular for members of Macaca fascicularis (Raffles, 1821) is “crab-eating macaques” per the standard for mammal vernacular names (Wilson & Reeder’s Mammals Species of the World, 3rd edition; Mammal Species of the World (, not “cynomolgus macaques” (even Wikipedia gets this right). Why microbiologists insist on calling these cynomolgus macaques is one of the great riddles I plan on solving one day – in my opinion they shouldn’t. And why most people insert an extra o when pronouncing it (“cynomologous”) is an even bigger mystery to me 😊

“Death as an endpoint” is a phrase I hear a lot on TWiV. Since more and more readers ask for less jargon and more clarity, I think this should be changed to “Euthanasia as an endpoint”. Studies with actual death as an endpoint, i.e., letting the animals suffer until they die, are thankfully very very rarely permitted by animal care and use committees. However, that has ramifications, because euthanasia criteria are typically not standardized across facilities, which makes across-facility comparison of results often challenging. In any case, it is important for the listeners to understand that it is typically a human who makes the decision when the experiment is over, which then however is portrayed as “death” in Kaplan-Meier graphs or as “death as an endpoint”.

“African green monkeys:

– green monkeys (Chlorocebus sabaeus)

– grivets (Chlorocebus aethiops)

– vervet monkeys (Chlorocebus pygerythrus)

These three species (and a couple of more) were once upon a time (many decades ago) one merged species called Cercopithecus aethiops and the collective members of that species were called “African green monkeys”. That term should hence not be used anymore, but instead the terms above should be used *once people actually figure out via mtDNA barcoding which animals they actually work with* (mostly, people still say “African green monkey” and then jump from Cercopithecus aethiops to Chlorocebus aethiops and simply decide that’s what they are working with…). PS: Yes, Vero E6 cells are actually grivet cells.



Vrr: Pathogenicity is the quality or state of being pathogenic, the potential ability to produce disease, whereas virulence is the disease producing power of an organism, the degree of pathogenicity within a group or species.

Pathogenicity is a qualitative term, an “all-or-none” concept, whereas virulence is a term that quantifies pathogenicity.

So when I say ‘virulence is the capacity of a virus to cause disease’ I am implying quantification. 

Jens agrees with this 🙂 

Lisa writes:

Dear TWIV team,

I am guessing that even if this is possible this would be too resource-intensive in many countries that use OPV, but if a recent OPV recipient or a close contact of a recent OPV recipient started to get symptoms that might be early symptoms of polio how possible would it be for a doctor to quickly determine whether the symptoms came from polio and interrupt the infection at an early stage and mitigate the risk that the vaccine would ever cause paralysis?

Also a listener pick that probably I am not the only listener to pick:

(The hepatitis discussion in episode 995 reminded me of it.)

Thanks for everything I learn from TWIV and from other Microbe TV podcasts! And congrats on getting to episode 1000 soon!


Austin, Texas

Stephanie writes:

Thank you so much for your podcast.I have learned so much and it makes me feel more confident in this complicated time.

Question – I have had my vaccines and boosters, went through Covid in January using Paxlovid, I am 72, my husband is 85, Were we to contract Covid a second time do we take Paxlovid again?

That question has never been clarified.

Thank you.

[according to Daniel – yes]

Katie writes:

Good Evening,

Blue Oyster Cult wrote a song entitled Godzilla that has a very pertinent set of lyrics in it:

“History shows again and again

How nature points out the folly of men”

In 2020 these lyrics would even randomly play in my head while listening to Twiv conversations about the fitness of SARS-CoV-2.

Thanks for all you do,