Mathilde writes:

Dear Vincent and colleagues,

I often listen to TWIV and always appreciate the discussions. I was very happy to see that one of our papers was discussed in TWIV 753! I am the first author on the study on flu transmission from the nose of ferrets. I just wanted to add a few comments about certain points of your discussion.

One comment about why we used silent substitutions to tag the viruses. We indeed took this approach, as Alan and Brianne mentioned, because of the constraints of the flu genome for reporter integration and the need to have viruses with the identical biological properties. A few studies have described influenza viruses carrying reported genes, but these are still attenuated or depending on the size of the reporter, genetically unstable. Other viruses that have less constraints on the size of their genome (i.e. CDV) can better accommodate reporter genes.

One comment about the last part of your discussion on measles. Colleagues of ours actually performed a study on CDV in ferrets as a model for measles ( They inoculated donor ferrets with three viruses harboring three different fluorescent reporters via different inoculation route (intra-ocular, intra-nasal, intra-tracheal), and placed recipient ferrets two days after inoculation in the same transmission set-up. In contrast with flu, transmission of  CDV occurs in the late phase of the infection and the three viruses that were inoculated in different sites were not compartmentalized anymore at the time of transmission. As a result, the dominant virus was the one that transmitted, independent of the site of inoculation. In contrast, we observed a strong compartmentalization of influenza viruses upon co-inoculation in the nose and in the trachea when we performed similar studies to study reassortment (

Regarding the discussion of aerosols originating from the LRT and droplets from the URT. I think that this needs to be taken with a grain of salt and should be very carefully extrapolated to the transmission of other viruses, like measles for instance. We also discussed in the paper other aspects like the possibility for droplets to become smaller to a certain extent via desiccation and the stability and viability of viruses in droplets of different sizes.

Finally, to answer the comment of Brianne about the impact of the inoculation route on the pathogenesis of the virus. This has been done on many occasions with human and avian influenza viruses. Here just one example with H5N1, where intranasal inoculation resulted in dissemination of the virus to the brain, whereas intratracheal inoculation resulted in severe bronchointerstitial pneumonia (

Thanks again for discussing our work, this was an honor!

All the best

Mathilde Richard | Assistant Professor | Department of Viroscience | Erasmus MC

Stephen writes:

“Fifteen Ways to Stay Free of Covid”

“The problem is all inside your head” She said to me
“The answer is easy if you
Take it logically
I’d like to help you in your struggle To be free
There must be fifteen ways
To stay free of Covid”

She said “It’s really not my habit to intrude
Furthermore, I hope my meaning
Won’t be lost or misconstrued
But I’ll repeat myself
At the risk of being rude
There must be fifteen ways
To stay free of Covid

Yes, fifteen ways to stay free of Covid
Just one little prick, Mick
To make you immune, June 
This ain’t gonna hurt, Burt 
And then you’ll be free
Don’t make such a fuss, Gus 
There’s no need to cuss, Russ 
So easy to see, Bea
How to keep yourself free

Just two shots to take, Jake 
Get it while you can, Ann 
Don’t want to beg, Craig 
Just listen to me
You won’t feel any pain, Jane 
It’s part of the plan, Jan
So easy to see, Lee
Two shots and you’re free

She said, “It grieves me so
To see the virus cause such pain
I wish there was something I could do
To make folks smile again
I said “I appreciate that
And would you please explain
About the fifteen ways?”

She said, “Why don’t we both
Just sleep on it tonight
Just understand the virus
And you’ll begin to see the light
Then she jabbed me with her needle
And I knew that she was right
About the fifteen ways
To stay free of Covid
Yes, fifteen ways to stay free of Covid

Just open that vial, Lyle
To get the vaccine, Gene
Just pull up your sleeve, Steve To stay Covid free
There’s no need to snarl, Carl
To whine or to moan, Joan
Don’t be a jerk, Dirk
As easy as can be, Dee
To stay Covid free

Two shots and you’re set, Chet 
It’s part of the plan, Stan
This vaccine’s not a scam, Sam 
Just listen to me
A tiny little stick, Dick 
We’ll do it right quick, Nick 
For you and for me, Bree 
Let’s stay Covid free

Carol writes:

Dear Vincent and friends, you were talking about Annie Lennox recently – so i thought you might like to see this.  Thank you all for educating us, the public at large.  Keep up the excellent work.

Best wishes


(just a communicator)

Dear friends,

A few weeks ago, I was fortunate enough to have been fully vaccinated against Covid-19.

I believe that everyone in the world should have the right to be protected from this potentially deadly virus.

That’s why I’m joining forces with the People’s Vaccine campaign, asking President Biden to join developing nations in calling on pharmaceutical companies to suspend the patents on Covid-19 vaccines. So that this life-protecting vaccine can become available to everyone around the world. We need to boost production in all parts of the world as soon as possible.

Please join me — take a moment to send an urgent message to President Biden using the buttons below, and ask your friends if they can do, too.

Annie Lennox

Chelsea writes:

Good morning, 

It’s currently a sunny 64 degrees Fahrenheit with an anticipated high of 90 here in Lincoln, NE. Hello first summer of the season!

My brother-in-law turned me onto TWIV a few months ago & I have added you to my podcast shuffle. Working in the lab, I listen to *a lot* of podcasts. 

This morning, I caught TWIV 745. As I got my degree with the pipe dream of working in a zoo & interning my college summers at the Henry Doorly Zoo & Aquarium in Omaha, NE, it was a fascinating listen. And imagine my surprise as I sit in front of my bench & hear guest Nadine Lamberski identify my employer – Zoetis – while explaining some of the gorilla treatments. It was a trip!

Just a small note though, it is pronounced “Zo-eh-tis” rather than “Zoy-tis.” No worries – my husband always pronounced it “Zoy-tis” too & when I interviewed with the company, I had to trick the interviewer into pronouncing it for me so I would know.

Have a great day!


Richard writes:

Please know my cattle enjoy TWIV, for your voices from my pocket signal fresh grass and hay.  My Dept Chair implored me to listen to TWIV.  And my graduate adviser stressed saying “Yes” to academic superiors whenever possible!

So my herd and I listen to TWIV together.  

I’m perplexed at cattle farmers who vaccinate regularly to build and maintain their own herd immunity for protection against various ‘wee beasties’.  Neighbors who know firsthand that unvaccinated cattle suffer and die.  Yet display reluctance toward vaccine efficacy and safety during this current, human pandemic.

Do you have a sister podcast:  “This week in Psychology?”

Can you recommend any links on engaging with vaccine reluctance?  

I secure my cattle in a head gate before jabbing each of them.  Such is not ethical in humans.

Adjunct Faculty 
King University
Bristol, TN

Eating heifer burger for lunch as I type, as she did not fit the herd phenotype we select for…

Iradis writes:

Hello TWiV-professors! Sharing a pick with you all again, since I’m on this space arc and can’t seem to crawl out of the rabbit hole. 

Incredible. Incredíble. 


Blue Pilgrim writes:

I just ordered a scythe (looking at them for years for mowing the lawn, learning and trying to find one I could afford) from these people, and looking further into the company I found  and thought of you guys, maybe Dixon especially, or the gardening fans. Please pass the information on to them. They are in Shelby Falls, Massachusetts.

Sometimes you gotta think about things other than viruses and biology — although there is a lot of biology involved in Howland Tools too, it seems. 

Love your shows and the TWiVers, etc. You are living treasures.