Volker writes:

Dear Vincent, dear TWIVos,

I’m writing from Bern, Switzerland, on a sunny but chilly day with blue sky and -1°C (30°F). 

As you know, the XVIth International Nidovirus Symposium is taking place this year from May 14th to 18th with the stunning backdrop of Lake Geneva at the Montreux, Music and Convention Centre (2m2c), Switzerland, and it would be good if you could announce this meeting in your TWIV podcast.

Over the past 40 years, the Nidovirus Symposium has evolved into a triennial event covering all aspects of nidoviruses and nidovirology.  This eclectic group of viruses are found in humans and animals and include pathogens such as SARS-CoV-2, zoonotic SARS- and MERS-coronaviruses, common cold viruses, and many other animal and highly relevant livestock viruses. The NIDO2023 meeting is co-organized by Isabella Eckerle (University of Geneva), Ronald Dijkman (University of Bern) and myself and we are happy that, with the help of our scientific advisory board, we could put together a very interesting scientific program (see: https://www.nido2023.com/schedule/scientific-program and attached pdf). Keynote lectures will be given by Dr. Mike Ryan (Executive Director, WHO Health Emergencies Programme), Prof. Christian Drosten (Charité, Berlin), Prof. Ralph Baric (University of North Carolina, USA), and Prof. Kanta Subbarao (University of Melbourne, Australia). 

You will notice that many of our keynote and invited speakers have been your guests in previous TWIV episodes, and we are excited that Vincent will join us to broadcast TWIV on-site. 

The deadline to submit abstracts and to secure the early bird registration fees is February 19th, but at the time when you announce the NIDO2023 symposium in TWIV, we may have already communicated an extension to February 28th. You can find more information and updates at https://www.nido2023.com 

We „nidovirologists“ are big fans of TWIV and we look forward to welcome you in Montreux!

Best regards,


Multidisciplinary Center for Infectious Diseases (MCID)

University of Bern

Alan writes:

Of course I know the Sverdlovsk incident involved B. anthracis, not variola, and I’m mortified I made such a howling blunder while discussing it. The point I was trying to make was that it’s another red herring often tossed out in the GOF debate. Proponents of increased restrictions cite it as an example of the dangers of infectious disease research, when in fact it involved not only insufficient safeguards, but also a category of research (bioweapon development) that was explicitly banned by international treaty even at that time.

In any case, I’m sorry for bungling my facts.


Bill writes:

In a recent episode of Kevin Folta’s Talking Biotech podcast, he interviewed Kevin Esvelt. 

Esvelt is a MIT professor, and at 4:45 in claims that “in fact” we’ve eradicated wild-type polio from the world, and that the only concern of ours now is the vaccine revertant strains. I think this is great news, not only has the disease been eradicated, but presumably the virus as well. Time to destroy those remaining type-1 stocks – or am I misunderstanding this?

After all, Esvelt is an expert on viruses, and CRISPR, and gene-drive, especially CRISPR gene-drive (which may be the first self-propagating biotechnology, dontcha know?). 

In fact, he seems to have coined the phrase to “boot up” a virus. Unfortunately, seems like he was scooped by the only paper to use this term in pubmed:


What other novel terms do people use for this technical process? Start-up? `chroot` ? Clutch start? Alan, is it safe to “hand prop” a virus?

But I think there’s really something here. Esvelt is the type who “simply runs the numbers” by plucking out estimates and weaves these with the simple eloquence of confidence into a quantitative argument whose only conclusion is that the de novo synthesis of a novel virus genome is how the world will end. I’m no expert, and I won’t even go re-download that one Daszak serology study for the numbers, but if you did: what frequency would you estimate that spillovers occur at, and what frequency do pandemics occur at? If you were simply to run the numbers, what kind of deathtoll (and other impacts) would you estimate would result? Just hypothetically, say across the last two decades?

And would that cost justify a research program to survey, catalog, and report the viruses found in human-adjacent zoonotic reservoirs?

Esvelt thinks it’s not worth the risk


Lainie writes:


I am a regular TWIV listener and wanted to chime in about your conversations regarding abacavir use and cellular senescence. I am a physician assistant, specializing in primary care and HIV care. I use abacavir in conjunction with other antiretrovirals (ARVs) to treat HIV in a handful of my patients. More commonly, other NRTI agents are the backbone of a complete ARV regimen.

First, to update you on the proper terminology, it is preferential to use the term “stage III HIV ” instead of AIDS due to the stigma associated with the word AIDS, and the mistakenly common notion that AIDS is a death sentence. Stage I HIV is an absolute CD4 > 500, stage II is CD4 count 200-500, and stage III is a CD4 count <200. 

Using the phrasing ‘stage III HIV’ more accurately reflects the idea that someone with a low CD4 count has the potential to recover their CD4 cells and immune function with proper ARV therapy. 

That being said, we can use abacavir in all stages of HIV treatment.  We always check an HLA-B5701 allelle (a blood test) prior to starting abacavir based ARV regimens since patients who carry this allele are at a higher risk of a hypersensitivity reaction to abacavir. I also counsel my patients on a potential for increased cardiovascular adverse effects (ie heart attack) with abacavir. There is conflicting evidence on this matter, but some (but not all) observational studies have shown increased cardiovascular disease and cardiovascular events. So in patients at high risk of cardiovascular disease, such as patients with diabetes, uncontrolled blood pressure, hyperlipidemia, or certain ethnic backgrounds, I review the possible link to increased cardiovascular risk and have a discussion with the patient whether they want to continue their current ARVs, or switch to a regimen without abacavir. 

Also, we routinely get bone density tests for patients living with HIV, starting at age 50. We do this because both HIV and some of the medications we use to treat HIV can cause decreased bone density. I agree, it would be very interesting to pull some data to compare the bone densities and/or charted diagnosis of osteoarthritis in patients living with HIV, comparing the ARV regimens to see whether abacavir is beneficial or not. Perhaps I will try to get approval to do that one day. 

Anyway, I hope the above information was useful. I can’t thank you enough for your podcasts. I really enjoy your honest and inquisitive dialogue. 


Lainie Heine PA-C

Albuquerque, NM

University of New Mexico Truman Health Services

John writes:


I listened with great interest to TWIV 958, especially about your comments on the density and movement of white-tail deer in the US and across the Canadian border. As a biogeographer who has been working to model and somehow get a handle on the data regarding deer density in the US, I thought you might like to look at a map my lab has created, using a whole host of data sources, including the US Forest Service and the USDA.


The map of sequences hCoV-19 for DEER for New York State—the data is from GISAID.


If you click on the interactive legend the map will highlight the density ranges. This data is another one of those “you would think we would know it” pieces of information—we really have no idea at the scales that would be of real interest and no real data on group interactions.

One of things my lab is most interested in, is the correlation between animal movement and the spread of disease, both animal and zoonotic. We currently know very little about animal movement ecology, especially in disturbed environments, and this leads me to my listener pick. There is a new book called, The Theory of the Spread of Epidemics and Movement Ecology of Animals (Cambridge University Press, 2021) which nicely summarizes some of what we know and the difficulties of modeling and getting the empirical data. It is a really complex problem and the field data on animal movement is sparse and nor systematically collected.

I love your podcast! Stay well.


John Hessler, FRGS

Lecturer, Johns Hopkins University

Director, Lambda Lab for Computational Biogeography &

Bioinformatics Research

Jessica writes:

I hope you like this.

Thanks for your wonderful podcasts.

Classic cases revisited: Oscar the cat and predicting death