Paul writes:

Hi Dr. Racaniello,

We lost a great Canadian microbiologist today. Dr. Don Low played a major role in the SARS outbreak and many other infectious diseases including Necrotizing fasciitis.

Keep up the great podcasts.


Toronto, Canada

TWIV follower since TWIV #1

Allan writes:

Dear TWiV crew,

Thank you for the very entertaining and informative podcast, I have been a fan for three years now. I completed a PhD in molecular virology in 2010 studying species-specificity of influenza viruses, and since then I have taken a global public health and epidemiology trajectory, applying my scientific background for public health surveillance and public health research. It has been a good direction for me, but I miss the basic research somewhat, and it is great to be able to stay abreast of molecular virology through your podcast. I am now living in Zambia, doing laboratory and epidemiologic work on HPV and cervical cancer as an NIH Fogarty post-doctoral fellow at the Centre for Infectious Disease Research in Zambia. Due to limited bandwidth in Zambia, I spent a year in Lusaka without any new TWiV podcasts. When I was back in the U.S. on vacation I made sure to download the entire past year, and I am now working my way through the past 11 months. My bicycling commute in Lusaka is more enjoyable now that I can listen to you guys again! Keep up the good work.



Steve writes:

Here is a short podcast segment that may be of interest:

CSIRO sends bird flu test kits to Asia

On the last podcast, TWiV 237 [1:02:30], Dr. Emerman mentioned the burst-like or episodic nature of retrovirus integration in the genetic record. Any idea what drives these bursts?

Dr. Emerman also voiced a thought from the literature on the origin of RNA viruses from the RNA milieu [1:03:56]. In a future episode it would be cool to hear TWiV question someone familiar with that literature.

TWiV does some standout interviews with some very interesting people about some very interesting stuff. I vote TWiV consider doing a longer interview (2-4 hour) now-and-then to cover the career of a prominent elder virologist or a topic in-depth just because its so fascinating.

Last, please consider adding TWiV 237: Paleovirology with Michael Emerman and TWiV 25: Viral Evolution to the Virology 101 series.

Neva writes:

Hi TWIV Folks,

Here is an article with a cartoon depiction of a flu virus suggesting the dangers of ill food service workers.

Bon appetite,


Buda TX

Suzanne writes:

I just finished listening to last week’s TWIV and had one question. Making sure there’s a paper trail for the distribution of this virus makes perfect sense. But I was wondering what reasons they’d have for not letting other people work on a diagnostic test. Is that just a money related thing or is there a more scientific related reason?


Jim writes:

The last ten minutes of Triangulation 109 talks mentions a dismal grant application approval rate of 8% from the National Sci Foundation for the last two years. Is there a place that shows the annual approval rate for the last ten or twenty years so one can see how 8% compares. That same segment lists petridish, scistarter, and microryza as crowd sourcing sites.


Smithfield, VA

David writes:

Have you ever done a podcast about Chicken Pox and Shingles? If not, do you think you could put one together at some point? I’m just fascinated by this virus overall. I’m really curious to know how Chicken Pox becomes Shingles, why Shingles is so much worse than Chicken Pox, how and why it lies dormant in our bodies after our childhood introduction, and what’s it doing in our bodies for 30 years while it waits to strike? How does it stay alive? So many questions…



BioTechnology Technician in Training 🙂

PS: The next time you’re in the northern California area, you have to visit our community citizen science lab

Curt writes:

Dear TWiV team,

My name is Curtis, I’m a paramedic in California, where it’s presently raining heat strokes by the bucketful- or as the locals call it, ‘sunny’. I listen to you guys every week, and Vincent’s Virology lectures have certainly livened up my five hour (round-trip) commute. I’m writing in to ask if RNA secondary structures have any effect on the mutagenesis or pathogenesis of a virus- or if there are currently any interesting new developments in viral RNA secondary structures.

On a related note, I wanted to bring a science crowdsourcing project to your attention: eteRNA, a joint venture between Stanford, Carnegie-Mellon University, and the Internet to build the world’s first library of RNA secondary structures, as well as to improve on RNA secondary structure prediction models. It can be found at I’d also suggest Rhiju as a guest for the show.

PS, I thought I heard Vincent mention something about a zombie plague on a recent TWi-, and that got me thinking. What does the TWiV team think would be the most likely class of pathogen to cause something like a zombie plague?

Thanks for your time, love the show, keep up the great work.

Kevin writes:

Hi there TWiV folks,

I’m in the middle of a paper push, so I’ve fallen a bit behind on TWiV and TWiM, but I did a marathon this weekend while cleaning the apartment and I wanted to comment on a couple of episodes.

During the discussion on viral resistance in the placenta in TWiV 241, a common question came up: why not leave the anti-viral state on at all times? I’m an immunologist, and when this question inevitably arises in introductory immunology classes, the answer is always that it’s too energy intensive or that things like inflammation are damaging to the host – indeed those were the answers you guys came up with as well. Because of the context though, I thought of a potential alternative explanation that I wanted to get your feedback on.

Is it possible that some antiviral mechanisms are held back to prevent viral evasion? If we used anti-viral miR-containing exosomes to deal with all viral infections, viruses would likely quickly learn to evade it. If a lot of viruses could evade it, using it to protect the fetus would be less effective. If instead, we’ve evolved to only use this strategy in the context of pregnancy, there would be less selective pressure for viruses to learn to evade it, and that might be positively selected for from the human side.

Of course, this presumes a lot of forward thinking to evolution, and I’m not sure selection can work so far removed from an individual’s survival. What do you guys think?


I also wanted to comment on another listener’s question in TWiV 242 about infections in long-lived species like redwood trees. The explanations offered on the show, that the speed of the hosts’ metabolism would slow the speed of the virus’ metabolism, or that these trees have superb anti-viral defenses didn’t sit well with me. Surely, if it was advantageous for the virus to use a much faster metabolism, they would be able to evolve to do so, and if viruses can evade something as complex as our adaptive immune system, it seems implausible that they would be unable to get around sap or anti-viral compounds.

Implied in the listener’s question, (and it seemed in your discussion of it), is the assumption that a pathogen’s goal is to kill the host, and the only reason that it doesn’t is because of the hosts’ defenses or some intrinsic limitation of metabolism. However, a pathogen’s true goal is to replicate and spread to new hosts, and will generally only kill the host by accident or if it’s advantageous to do so. Pathogens that replicate and kill their hosts rapidly will rapidly die themselves (think: ebola), unless they have an incredibly efficient mode of transmission. Since trees don’t tend to move around much (we’ll leave discussion of Ents from Lord of the Rings aside for now), transmission opportunities are likely to be limited. Viruses that infect long-lived tress and kill them quickly might pop up occasionally, but they aren’t likely to be very successful.

This idea, that the virulence of a pathogen is dependent on the pathogen’s mode of transmission rather than on the host’s ability to defend itself was first introduced to me as an undergraduate at UCSD by Stephen Hedrick, and it’s one of the things that catalyzed my interest and host-pathogen interactions. If I had learned it in the context of a microbiology class, I might be in a different field right now, but Dr. Hedrick taught immunology, and he’s the reason I’m working on my PhD in immunology now.

Thanks for the great shows! I don’t read as many papers as I should, and when I do they’re about the nitty-gritty of biochemical signaling in the innate immune system, it’s great to have an entertaining way to get some broader perspective in order to remind me of why we care about all this stuff anyway.


5th year (almost 6th year) PhD candidate in the Harvard Immunology Program

P.S. Regarding another listener’s comment about a desire for a public-health/epidemiology focused podcast, I’ve had similar thoughts regarding an immunology- focused podcast. I’m interested in starting one myself once I get this paper submitted, modeled on TWiV, TWiM and TWiP – if that gets off the ground, would you be willing to offer advice (and maybe a TWiV bump when the time comes)? Thanks again!

John writes:

Dear TWIVvers,

This article is a really cool story: the guy who was the last recorded smallpox case in Somalia ended up devoting his life to trying to eradicate polio.

Peter writes:

Dear TWiV team

Just writing to bring to your attention this two part BBC World Service documentary about the SARS outbreak of 2003.

(Part one is only available for download until September 10 2013)

The story of SARS: Kevin Fong explores the personal and medical impact of SARS ten years on:

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