TWiV regularly receives listener email with corrections, comments, suggestions for show topics, requests for clarification, and additional information. All are archived on this page.

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Letters read on earlier episodes of TWiV can be found on this page.

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247 comments on “Letters

  1. I am a neuroscientist but have a side interest in germs. I really enjoy your podcasts. Rodney has a lot of opinions that I have been subjected to over the years. I think he would make an interesting guest.

  2. I just finished listening to episode 51 and have a follow up for you on Virogenetics. They were taken over by Sanofi. The technology on which the vaccine was developed goes back to 1995 for the ALVAC-HIV patent. There are 3 people on this patent. Paoletti, who Rich mentioned, Jim Tartaglia who now works for Sanofi and Bill Cox. Bill was the immunologist and he quit science to fly packages between Albany and Newark.

    My understanding, through Bill, is that since the vaccine was designed to work against 2 strains the lack of higher efficacy may be due to other strains. This is quite possible in a place that is known to be a destination for sex tourists. It will be interesting to know which strains the infected people in the vaccinated group were infected with. They must have collected these data and it is not that difficult serotype or genotype, is it? Is the problem that the patients are infected with multiple strains? I feel like the scientists involved in this trial are holding something back. Perhaps they are waiting for a big meeting to have a press release but that is more of a big pharma maneuver.

  3. gtolle Oct 7, 2009

    TWIV 47

    Still catching up! Not rushing through. Savoring each episode. Sorry if this has already been addressed.

    Dick, congrats on your op ed on vertical farming. Keep in mind that the most overall efficient system would be a permaculture (simplified eco-) system so there would really need to be lots of wee beasties running around to balance the resource cycling.

    As for the magic no-virus switch:

    1) Human illness would almost certainly increase almost immediately upon throwing the switch. I can't imagine that bacteriophages are not an essential component of human health. It will be interesting, however, to find out if the human immune system coordinates with some bacteriophages.

    2) Viruses would come back fairly quickly (at least some of them) unless the switch also eliminates retroviruses hidden away in various genomes around the world.

    3) I believe that viruses would probably re-evolve eventually as I believe that they are related to microbial gene transfer systems. I suspect that the reason that we haven't seen novel viruses evolve lately may be related to A) there are a limited number of core viral types (the equivalent to the theoretical minimal genome for microbial life) and B) the niches that they could fill are already occupied. Hence, a novel virus might resemble a pre-existing virus sufficiently to confuse its origin and there is little pressure for one to evolve from current gene transfer systems.

    Keep up the good work.

  4. Daniel Oct 17, 2009

    Hello. I listen regularily to your Podcast, and I've come across a video about FluMist and a conspiracy theory in general. Would you mind watching and commenting it from a scientific point of view (leaving all that conspiracy stuff out).

    Kind regards,

  5. Daniel Oct 17, 2009

    Hello. I listen regularily to your Podcast, and I've come across a video about FluMist and a conspiracy theory in general. Would you mind watching and commenting it from a scientific point of view (leaving all that conspiracy stuff out).

    Kind regards,

  6. euthanasiaforgeezers Feb 9, 2010

    I was just listening to your podcast on plaque and you mentioned how much fun it would be to make time lapse movies.

    You can make your own movies.

    I too wanted to make time-lapse movies and ran across an electronic shutter control that works on regular digital cameras. Reading from their list, their product is compatible with canon, nikon, pentax, samsung, olympus, panasonic, sigma, leica, minolta, sony, fujifilm and kodak.

    With one of these timer/shutter controls all you need to do is scrounge an adapter for your camera lens to fit on the microscope and you're in business. What's really great about it is that it's extremely easy. Even a virologist can do it.

    After you've taken several thousand photos (in JPG format) over a period of several days (you program the interval between shots) you use a shareware program (JPGAvi) to convert them into an AVI format movie. The website for the timer is… and the website for the JPG to AVI converter software I use is

    For about $60 (including shipping) you can make your very own time-lapse movies. If you have any problems you must know some 12 year old kid who can help you get up and running. Maybe Dick can do it.

    If you have a decent camera and can take acceptable quality pictures with it you'll be able to produce a professional quality time-lapse movie on your very first try. I'll say it again – it's easy.

    I enjoy your show.



    • We just had a case of a cheating brain-scientist, who now has been
      convicted of using research money for clothes and stuff, trying to blame
      this on one of her students and faking mouse-experiments results. It
      was quite clear that the system isn’t really geared towards handling
      these cases.

  7. Dear Twiv Guys/virology gurus,

    I really need your help. Let me preface this by saying that I have a slightly exaggerated fear of germs which is probably why virology fascinates me so much. I need your collective brainpower to explain something to me. My question has to do with AAV vectors. I’m specifically wondering about the ones people use in the lab but this also applies to gene therapy vectors. Supposedly these vectors are replication defective. The replication factors are supplied in trans to make the virions, right? In neuroscience this is frequently HSV so I call it AAV in a herpes suitcase. If HSV and AAV can supply factors in trans, why can other related viruses that might be lurking in the mouse or person? I’m sure mutations and recombination figure into this as well but how safe are these vectors? Given the number of viruses in the world and the constant evolution can you really guarantee that a virus is replication defective? I would like someone who knows something to explain the science because I don’t see how you can. Sure, it is a remote chance of replication but it isn’t completely out of the question, right?

    Thanks for the education. I love the podcasts and have even listened to the lectures. It is great to be able to listen to lectures from courses I wish I had the time to take. Hopefully this will catch on and people more people will realize that science education isn’t just facts and lectures. I’ll take TWIV and TWIP over network TV any day.


  8. Wonderingalice1984 Aug 8, 2011

    I just wanted to say thanks! I love TWIV! I’m just interested in virology. (My degrees in K-6 education) I’ve learned so much and spent many an enjoyable hour with you guys! Keep up the good work! – Jocelyn Johnson

  9. Assaf Lowenthal Aug 10, 2013

    Hello TWIV team,

    I am a microbiologist from the Hebrew University in Jerusalem Israel, currently spending my time making wine and beer (not drinking, at least not that much…). Naturally, I started listening to the TWIM podcast, but very quickly ran out of episodes and started listening to TWIV. I was waiting for a good reason to write and unfortunately there’s a good one now. You might have heard that during the last several weeks Polio was detected in Israel. It was first detected in the south, in a town small town where the population is not very strict about getting vaccinated. This week our ministry of health began a campain for vaccinating (OPV) kids in the south and in the center of the country . I’m sure you explained it previous podcasts, but could you please explain why a kid who got the dead vaccine (that would be the vast majority of the population) should get the attenuated one? The ministry of health says that the purpose of this vaccine is to reduce the number of carriers in the population, and that there is absolutly no danger in vaccinating. But, what about vaccine-derived polio? More personally- I’ve got a 11 month baby- her third and last vaccine (dead virus) is schedulaed for next month, my gut feeling tells me not to give her the OPV, would you share your thoughs on the subject? Also, as a microbiologist many of my friends ask my opinion on the subject, I’ll feel much more comfortable answering them after hearing your advice.

    Thank you for many hours of fun and eduction

    Assaf Lowenthal

  10. Ken Kahn Dec 17, 2013

    Just read this Technology Review article about Angela Belcher who is designing viruses to make better batteries, solar cells, cancer diagnostic tools, and more.

    Might be a fun topic for a future episode.

  11. Nicola Cataldo Mar 23, 2014

    Dear Doctors,
    I am among those who wish I had studied virology instead of the direction I did take and I want to thank you for the podcasts that seem to be offering me a second chance, here in my retired years. I started with TWIV Podcast #125 because it was the earliest I could find (why is that, anyway?) and I’m up to Podcast #260 already.

    Given how much viruses effect the daily lives of all of us, it seems like everyone would want to know something about them and the thing that sent me on this quest was the lack of information available to laymen on the subject. In your podcasts you often tsk-tsk the amount of Woo Medicine that circulates and I think I can point you to a very reasonable reason for this: the (clinical) medical community is doing a pretty terrible job of providing consistent information. I think if you review the information websites of even the most progressive major hospitals in the country, you will see a spate of contradiction and outright error.

    Some time ago, I asked a doctor friend of mine whether a person can contract the same virus more than once. Her answer was, “Sure, why not?”

    I pointed out that if that’s true, it is hard to understand why she recommends getting flu vaccinations. And having learned a few things in listening to your podcasts, I know understand now that, depending on the specific virus, correct answers could include Yes, No, Sometimes, and We don’t know. But her glib answer served no purpose at all.

    So this is in defense of the layman who might be suffering from Chronic Fatigue Syndrome or whose children seem to get one virus after another despite the annual vaccines, and who can’t get anything from his doctor but double-talk. You can hardly blame this patient from latching on to something. And if the medical community wants more trust from the patient community and less quack medicine, they need to start taking seriously their obligation to provide intelligent answers. Maybe you have some opportunity to survey the informational sites of legitimate hospitals and review the quality of the information therein.

  12. WanderingGnoma Sep 11, 2014

    Dear TWIV-team,

    Here are a couple notes from a clinician.

    If one considers the entire human organism, there are simple answers to the question in TWIV #295 about the viability of cells missing either the X or Y chromosome.

    The Y chromosome is clearly not required, given that no cell in a woman has a Y chromosome.

    By contrast, the X chromosome clearly *is* required, given the existence of lethal X-linked recessive disorders. For example, ornithine transcarbamylase deficiency is classically lethal in males, but not in heterozygous females. Normal males have one copy of the gene coding for the Ornithine carbamoyltransferase enzyme on their one X chromosome, and this is sufficient for good health. Having zero functional copies, however, results in death neonatally or in utero. The enzyme is essential in the cellular urea cycle.

    Also, in TWIV #298, SPECT (single photon emission tomography) is not the same as CT (computed tomography).

    A CT scanner shoots X-rays through the patient (or sample), which are then collected and processed into an image. In SPECT, however, radioactive elements inside the patient (or sample) emit photons that are collected and analyzed. PET is similar to SPECT, except that PET collects emitted positrons.

    Keep up the great work!

  13. Richard Ocepek Feb 3, 2015

    Greeting men and women of TWIV.

    I listened to your Jan 30 podcast and was a bit surprised you did not discuss the current measles outbreak in the US. I am 70 years old and recall having mumps and chicken pox as a child but do not recall having measles. This has concerned me somewhat over the years but I was not overly worried because the disease was essentially eliminated in the US for a long time. I was a pilot in the USAF and visited a bunch of places in the world that I would never pay to visit. I also lived in the Middle East for 6 years and have visited about 30 countries.

    I have often wondered if I did in fact contract measles as a child and the symptoms were minor and overlooked; or I have a natural immunity to the disease; or I am at risk to contract the disease in my later years? What are your comments on my situation? What are the pros and cons of getting a measles shot at this point in my life.

    P.S. Thanks for the straight info on the Ebola outbreak. Turns out you guys actually knew what you talking about which was quite different from the talking heads on TV.

    It is currently drizzling rain in Houston at 6:20 PM with a temp of 45 degrees.

  14. Katie Jan 15, 2016

    Greetings TWIV,
    I am an Immunology graduate student from Iowa State University that studies coronaviruses in pigs. I have loved listening and reading along with you since I started my graduate career 3 years ago! My friend shared this link with me and I thought other TWIV/TWIM listeners may find this interesting as well! I’ve always wondered what microbes make up my microbiome! There is a special for 5 site microbiome testing. They have a discount special running through 17-Jan-16. See the information below. Thank you providing this wonderful podcast as well as other great resources! I am continuing to explore this wonderful world of infectious diseases.

    5-for-1 Sale!

    Do you track how well your new year’s resolutions are working? Why not get a snapshot of your microbiome today, and see how it changes as you do. Here’s to the very best of health for you in 2016.

    Starting right now, a 5-site microbiome testing kit is just $89 instead of the usual $399.

    You can meet all the bacteria currently living in your gut, and also learn about your mouth, nose, skin, and genital microbiomes at the same time.

    Offer valid until Sunday, 1/17 at midnight, or while supplies last.

    Use discount code 5FOR1JAN when you checkout at

    P.S. The weather is currently -7 degrees Celsius and light snow flurries; a mild winter day for Iowa!


    Apparently drinking moderately boosts monkey immunity and enhances vaccine effectiveness. Any commentary from the TWIV Team?

  16. Michael Lane Oct 25, 2016

    I love TWIB, TWIM and TWIV – I grew up in a medical family – it skipped a generation, cuz I turned down Harvard or Yale for a music education. My mom was a nurse, my son is turn. ONE OF YOU has a Limerick contest – most likely expired, but here’s my entry:

    There once was a virulent virus
    which tried with all might to retire us
    We know it’s a pest
    But hardly the best
    I’m sure that you know Miley Cyrus

  17. Michael Lane Oct 25, 2016

    for the limerick contest going on on TWIM, TWIB or TWIV (all addictive) here is my “I’m sure it’s turned in too late” entry, after a foreward…

    I love TWIB, TWIM and TWIV – I grew up in a medical family – it skipped a generation, cuz I turned down Harvard or Yale for a music education. My mom was a nurse, my son is turn. ONE OF YOU has a Limerick contest – most likely expired, but here’s my entry:

    There once was a virulent virus
    which tried with all might to retire us
    We know it’s a pest
    But hardly the best
    I’m sure that you know Miley Cyrus

  18. Michael Lane Oct 25, 2016

    I love TWIB, TWIM and TWIV – I grew up in a medical family – it skipped a generation, cuz I turned down Harvard or Yale for a music education. My mom was a nurse, my son is turn. ONE OF YOU has a Limerick contest – most likely expired, but here’s my entry:

    There once was a virulent virus
    which tried with all might to retire us
    We know it’s a pest
    But hardly the best
    I’m sure that you know Miley Cyrus

  19. STeven Severance Nov 6, 2017

    COuld you have Nigel Goldenfeld on TWIV? His recent work on phages developing the genomes of bacteria seems facinating.

  20. Hello Dr Racaniello! I am a tenured investigator in the field of viral pathogenesis based in India and recently (through a colleague) heard about Twiv. I’ve decided to listen to every podcast from the first (West Nile) which by the way was broadcast during my post-doctoral stint at NCI-Frederick in Fort Detrick. Congratulations on creating a fun, educative and yet erudite discussion/forum. I was particularly intrigued by your 2nd show, on polio and would’ve loved to hear more about the SV40 contamination issue. Also, India is now polio free and we use the Sabin vaccine. Looking forward to carrying on listening!

  21. Scott Mar 7, 2020

    Greetings TWIB – Thanks for your ducational podcast. What is the driving the high rate of covid-19 cases in Iran and Italy? Higher rate of travel to China? Are most other countries just under-reporting?

  22. Joe Kuper Mar 19, 2020

    REF: CORONA VIRUS comes here by cargo ship
    all the sailors had it. They are not sick.
    If they were sick in their previous port, they were left there.
    What would happen if this was the year 1960.
    The virus would leave the ship and spread
    out all over.
    Of course ” it would play out”
    and we did nothing special about it.
    WE Did not talk about it, except to complain.
    We Did not even know that something dangerous
    was going on.

  23. MONIQUE DAGENAIS Mar 24, 2020

    I am a science teacher in Alberta, Canada. (grade 7-9), teaching from home. So many questions from my students.
    Is there a risk of contamination from food products ( not people) when ordering or picking our food in groceries store ?
    I wash all my containers but Is rinsing our produce enough since not using soap.

  24. Emily Mar 27, 2020

    I am a structural biologist who studies various soluble and membrane proteins using X-ray crystallography and cryoEM. So I understand only the very basics of serology, that an ELISA can be used to detect the presence of antibodies by detecting the presence of binding of antibody to a particular antigen that’s secured onto the ELISA plate; in the case of SARS-CoV-2, that would be the glycosylated spike protein.

    I understand, too, that the glycosylated spike protein on the surface of some viruses, like SARS-CoV-2, must necessarily, and so do undergo many structural changes dependent upon binding to their receptor and probably to antibodies and dependent on the stage of viral infection after the infected cell engulfs it.

    I know too that it’s difficult to produce the viral spike protein for use in ELISAs (and other experiments) in the lab without cutting off the part of the spike protein that would be embedded in the viral membrane. So making a soluble version of the spike protein is one approximation to the real thing, and another is the level of glycosylation on the spike protein. SARS-CoV-2 has something like 22 predicted glycosylation sites, which is difficult to get ‘right’, I assume, depending on which expression system one uses in the lab to make enough of the protein to put into ELISA-based serology tests.

    So my question is this: how do we know which protein to make for serology tests to best approximate what’s on the surface of the virus, and so what the immune system has seen or would see (for vaccinations)? Making the wrong approximation may cause serology tests to miss antibodies or to misrepresent which antibodies bind the actual spike protein.

  25. Benjamin Alexander Mar 31, 2020

    Dear TWiV,

    The Covid-19 mitigation effort undertaken in Wuhan seems always to be described as a successful intervention. My question is this: how can I convince myself that the infection was controlled through Chinese policies, as opposed to slowing due to herd immunity? I keep getting stuck on two pieces of evidence:
    1) the government isolated people who showed fever or other symptoms, but we believe that there may be large numbers of people who are asymptomatic spreaders. If the asymptomatic spreaders were quarantined then the new symptomatic cases would keep showing up.
    2) relaxation of the travel restrictions does not seem to be leading to a resurgence in cases.
    More generally, is there some other evidence that allows us to differentiate between a model of Covid-19 disease where most people who become infected with SARS-CoV-2 get really sick, versus a model where infection in the population is more common but with only some people becoming terribly ill, while others may have only mild symptoms or be asymptomatic?

  26. Wonderful podcast.
    I’ve encouraged all my friends and neighbors to listen and to contribute.
    Your voices sound like the voice of truth; I’ve stopped watching “briefings.”
    You take enough time to allow truth to gel.
    Locally, someone has even tried to translate your episodes in a blog, but there must be something lost in translation.
    Do you worry about the way your information gets passed on with deletions, transcription errors and mutations along the way?

  27. Dr Andrew Mellon Apr 13, 2020

    Listening to episode 600 there was a comment abut infecting viral load and what was known about this. My initial thought as a paediatrician was that VZV might provide an answer to this based on the clinical observation that siblings of primary cases often seem to have more severe disease. I am very conscious of ascertainment bias and couldn’t find papers to support that infecting load hypothesis. I did however come across this paper looking at influenza in a mouse model and the relative impact of a lower dose vs higher dose infecting load on many of the parameters that are of major interest to clinicians at the moment . High dose alters the clinical impact on mouse well being, amount of viral amplification, the cytokine responses including IL6, the degree of lung damage seen and the nature of the persisting tissue response. Some interesting observations about persisting immunity and potential for severe reactions to later high dose re-infection in mice infected with low viral load during their primary infection, that might add weight to the importance of those who have had Covid 19 not assuming they are safe. Who knows if this will turn out to be most relevant to those who find they had asymptomatic Covid 19 infection if that turns out to correlate with low viral infecting load .
    Please keep talking science. I will be spreading the word.

    All the best, stay safe
    Dr Andrew Mellon
    Paediatrician Sunderland, UK

  28. James L. Beede, RN Apr 27, 2020

    When I listen to the coverage of covid-19, the thought processes of everyone seem to be very fragmented. Is there a comprehensive list of questions that need to bee answered to get control of the pandemic? Also, is anyone appending citations for the papers coming out to said list of questions? Is there any way us educated laypeople (I am a registered nurse) can help?

  29. Carter Newton May 1, 2020

    I am a cardiologist and wonder why I never hear a reasonable discussion of plaquinil in your podcasts or lectures. I have listened to all your Virology course lectures (bravo, they are fantastic), and given your intricate knowledge of all the pathways of successful viral entry and escape, I wonder why none of the equally well known actions of hydroxychloroquine within and without of the target cell does not invite you and your expert panel to consider its potential value. I even (sadly) wonder this may be an academicians aversion to a republican president overall health policy failings. You are the best of the best to take this on. A vaccine is a distant hope, antivirals will probably only offer hope for the ICU cases, and yet here we are “opening up” and the prophylactic value hydroxychloroquine in nursing homes for example could be enormous. It should be considered by experts like you. Also a helpful fact is that n the 50+ years of plaquinil use for treatment of malaria and prevention and for autoimmune diseases , there has maximally 40 documented fatalities attributed to the drug, and those case with for multiyear use in high doses. Think about that and ask if any other drug or vaccine can make that claim. The QT issues (my speciality) never materialize. Here is the link that reveals that fact. It should be read in detail to appreciate the depth of the analysis.

  30. Al Aburto May 8, 2020

    Greetings to all TWiV’ers. You are all awesome, and what you do is much appreciated! Thank you!

    One question:
    Why the hell are we not testing more? I just can’t understand this! It is unscientific!! Where is the blockade? Is it the CDC? The CDC has smart people, scientists! What the hell is holding them back! What can a lowly citizen do to get the US Government (CDC) off the blocks and running?

    I’m from San Diego and the only way I can get a test is to have a note with permission from my doctor! This is crazy! I want to go in the backyard and scream!!

    Keep up the good work!!

  31. Neil Ravin May 15, 2020

    TWiV has become my main source of information about COVID19 and viruses beyond–apart from the NEJM and the New Yorker–my only source.
    I wanted to offer a quibble which, I’m sure, you’ll hear about from others, and an aphorism to address Dr. Racaniello’s question about knowing vs unknowing ignorance.
    First the quibble: I’m not sure if Rich Condit was joking when he started the TWiV podcast about Jenner and vaccines by saying “lymph” is simply “pus.”
    For listeners who may not have gone to medical school, lymph is actually the milky stuff–the word lymph comes from the Latin “lympha” which means “connected to water”–and it circulates in a network of lymph vessels which collect flow from cells, lymph nodes, (which include the spleen, tonsils) and ultimately connect with the parallel and better know circulatory systems of veins, dumping its “sterile” contents–I know Dr. Racaniello is very careful about words, and if viruses circulate in the blood I’m not sure we can say either lymph or blood is truly “sterile”–but the lymph dumps back into the blood stream at the thoracic duct in the chest and at other smaller stations. You can actually do a “lymphangiogram” to see this lymphatic system of lacy vessels from the foot to the thorax.
    “Pus” on the other hand, is the purulent exudate emanating to the surface from wounds, like the pustules on Jenner’s cow, which is not sterile–far from it–and contains bacteria, detritus of the fight offered by the innate and adaptive immune systems, It is “contaminated” with infective agents, along with the battlefield litter of T and B cells, antibodies etc. (Before Semelweiss and the concept of “sterile surgery” took hold, surgeons used to go about their rounds with “good pus” on their coats. Of course, there was no “good pus,” only “dirty pus,” but doctors and surgeons were ignorant then.)
    A small point, but I’m sure you’ve heard from a lot of clinicians about this, especially surgeons who are very wary of ligating, inadvertently, the thoracic duct when they are operating nearby.
    As for the aphorism: Dr. Racaniello was searching for the phrase to elucidate ignorance. When freshly graduated medical students, new doctors, arrive on the wards to start their internships (now called the PGY1) the are told: “The most dangerous intern on the ward is not the intern who does not know; it is the intern who does not know he does not know.” The message of course is: be humble, ask. Don’t pretend to know what you do not know.

  32. Vincent and team: I work in the healthcare industry (mostly Pharm). I have recently gotten hooked on TWIV and also binge watched your Virology course. You often express the incorrect view that industry only works on things that will make money and therefore it is an improper model for addressing things like novel viruses. The healthcare industry works on many things beyond profit motives. Take a look at the PHC arms of many of the leading Pharm companies and you will see development programs for things like deworming children, new HIV therapies sold at cost to the third world, Ebola vaccines, treatment resistant TB drugs and many others that will not turn a profit. It is true that private companies must generate profits but it is not true that they will only do things that will generate profits. It would be better to think of therapy development as an ecosystem in which many different types of organizations participate including for profit companies, philanthropic organizations such as Gates, the government, and academia. The degree to which they work together, often for non-profitable projects, is something most of the public is unaware of. Other new models Of development may also be desirable but to say the industry won’t look at a disease or condition if it is not profitable is not correct. It also feeds into the atmosphere of distrust that contributes to things like antivax sentiments and the like. Anyway, let me just end by thanking you all for your contributions to understanding (even if I think you are wrong on this point).

  33. Oops, seems I incorrectly attributed comments about the role of for profit companies in vaccine development to TWIV when the actually came from Virology 2020. I stand by the comments but they clearly should not be directed here. Anyway, love it all and truly appreciate the science outreach.

  34. Richard Taylor May 27, 2020

    Richard from NZ.

    Here, as we shut down in March and used quarantine, social distancing as well as lock-down; and we shut borders except for essential travel, (masks are optional for the public but a lot use them). the Govt. supported people on rents and mortgages etc and provided other funds (but it impacted on the economy): we seem now virtually clear and we are out of lock-down but still under rules of contact tracing etc. In about 4 weeks we should start interaction with Australia and later international travel in and out might be resumed. Overall NZers are supportive of the Govt. and science / medical advised response. [But. Now in Auckland there is a drought. First rain for about 3 months the other day. Cant win them all!]

    But it appears we have succeeded so far. The economy is under pressure but I think it is overall good and there were I think only about 30 deaths. All tragic but not large, although our population is low (5 million).*
    I am 72 and just continued exercising, walking, reading etc. I watched the Virology lectures, or some of. Have studied bio, chem etc years ago and could follow a lot of it. I read widely and had been reading — before all this all happened re the Pandemic — a journal of reported issues and things of interest in maths. A woman was talking about the probability or not of the segments (8) in a type of influenza virus either ‘reshuffling’ in some kind of logical order. rather than randomly.
    I cant recall what type of virus, apart from it being a coronavirus, the Covid-19 virus (or SARS etc) is. Is it similar to influenza in type, and does it have segmentation?
    Also is it known how the 1918 flu virus mutated? Did it have segmentation?

    Your lectures on viruses are fascinating. I can watch all but even those I have watched I have learnt knew things. Thanks. And I find the lecturer’s voice and enthusiasm kind of comforting. Strange, not sure why. But thanks.

    *I don’ think we can just divide say 300 by 5 and say our figure would be only 60x as large (about 1800), I think the math (maths here!) would involve and exponential formula. Still , being an Island, keeping to a good system, etc, seems to have worked well. Touch wood.

  35. Paul Offit, MD May 30, 2020

    I just finished listening to the latest episode of TWIV (episode 620) featuring an old lab mate, Dr. Jon Yewdell. Jon and I trained together in Walter Gerhard’s lab at the Wistar Institute in Philadelphia. I wanted to tell you how much I enjoyed the conversation. Jon was, as always, brilliant. There was one statement that was made, however, with which I disagree. Specifically, that no vaccine has ever performed better than natural infection. In fact, several have. For example, natural infection with tetanus does not confer protection against reinfection because the quantity of tetanospasmin necessary to induce symptoms is sub-immunogenic. Also, children less than 2 years of age don’t make good polysaccharide-specific immune responses. By conjugating Hib and pneumococcus to proteins, making for better T-cell dependent B-cell responses, vaccination with conjugated Hib and pneumococcal vaccines in children less than 2 years of age is better than natural infection. Indeed, children infected naturally with Hib are still recommended to receive Hib vaccine. Finally, the virus-like particle HPV vaccine also induces better, higher-titered immunity than natural infection. Keep up the great work. I can’t begin to tell you how much I enjoy listening to this program.

  36. Felicia Berke May 30, 2020

    I went to a socially distanced birthday party where the birthday girl threw a blanket over her head and hugged her loved one. I’m not sure if that’s foolhardy or genius. Is it safe to hug if you don’t directly breathe on each other?


  37. Inevitably on CNN’s website, when they announce a new outbreak of Covid-19 in a foreign country, it is accompanied by pictures of workers in white Tyvek suits spraying disinfectant on the streets. Does that actually do anything?

  38. TWIV 625
    I am sure you two have good reasons for not wearing masks while visiting an octagenarian. Please let us know what those reasons are! Otherwise you just appear to know better than everyone else and feel free to break virology spreading rules.

  39. Dear TWiV,
    Thank you for a wonderful podcast that I have spent hours listening to while mostly stuck at home. 🙂

    I saw this article and it went mostly zip right over my head. Do you think Yuri Deigin’s post is worth considering further? He speaks of “chimeras” and it made me wonder about viruses invading other viruses and exchanging genes. Does that happen? Is there “lateral gene transfer” going on between viruses? If so then wouldn’t that make virus genetic trees generally useless (can’t think of a better word)?

    Here is the link to the article:

    Keep up your awesome work!
    Best Wishes!

  40. Steve Griffin Jun 18, 2020

    Hi Guys
    Hot news on the BBC on 17th June . Dexamethasone is being hailed as a great British treatment breakthrough. As a big fan of your pod casts i have listened to your comments of time critical steroid intervention treatment of cytokine storms since April. Our NHS is well placed to do clinical trials i respect that but could you put this story into context please.
    A big hi to cousin Daniel keep up the good work
    Best Regards

  41. Elayne Jun 18, 2020

    Regarding your comment about Jewish funerals, yes, burial within 24 hours of death is the gold standard. This was more achievable when people moved less often and less far away from family. These days, burial is often delayed for several days while family travel from other states and other countries. In addition, bodies must often be transferred to other states for burial in family plots.

  42. My oldest dog, I Hero, would like to know whether or not squirrels are a possible repository for Sarris Covie too. She would be happy to help collect them for study if necessary.

  43. Richard D Fearnow Jun 28, 2020

    I am not aware of this being done but I would like to see an educational program set up by the health dept. A designated person & could be a volunteer to learn of patients diagnosed with Covid-19 and interview them if they are well enough to talk. Questions could be asked as to where the patient was & what he was doing 8-14 days before to determine how he might have acquired the virus. Stories can be reported in the newspaper & TV so the public will learn of specific patients behavior which lead to their infection.

  44. Dear TWIV,

    I second all of the gratitude expressed in the letters you read. After hearing the excellent curated information on this show, I’ve been following up by pulling the papers and discussing selected ones (in addition to other stuff I come across) with friends and family on weekly “coronavirus open house” Zoom sessions, advertised on Facebook. So far, I’ve not managed to attract any of my nonchalant friends/relatives on the other side of the political spectrum to join, but hearing the pertinent statistics on this show allows me to respond quickly and with good information to posts like the following two articles. I find it so very ironic that the only data they discuss in the first link is an image of the U.S. coronavirus cases timeline on 1poin3acres. They say, “Defining risk is an exercise in power,” and link to an article which purports to suggest that epidemiological outcomes in Italy, Sweden, Israel, and the U.S. have been “the same,” regardless of different control measures implemented by governments. The “data” that’s supposed to show this links to a pdf file in an Israeli math professor’s personal Google drive, written in Hebrew… Nobody cares about careful review of facts over there! …This “Why Facts Don’t Matter” article, SO VERY IRONICALLY, goes on to explain why they (libertarians) will never get through to us (people taking COVID-19 seriously) with (their) facts, because of (our) confirmation bias… They go on to eloquently define confirmation bias with good citations for it.

    I am *just* a chemistry professor, enjoying all the fabulous interdisciplinary science that is being poured into this global problem. Thanks for all you do.

  45. Cookieboy Jul 11, 2020

    I don’t know what the mortality figures at this period of the year are usually for all causes before Wuhan virus compared to with Wuhan?
    My question is, have deaths for other ailments dropped, and taking into consideration the 1.2% increase due to an aging population, are the figures that unusual?

    PS: What’s bigger, Mr Bigger or Mr Biggers’ baby?
    Mr Biggers’ baby is a little Bigger!

  46. Jamie Ferguson Jul 15, 2020

    Dear TWIV,

    I don’t recall you touching on the question of how having pre-existing viruses (as pre-existing conditions) adjusts your odds ratios with COVID-19. HIV and Herpes are obvious chronic conditions that spring to mind, as well as tick-borne viral illnesses, or auto-immune mysteries like alpha-gal. It made me wonder if Viromics was going to be studied in the Global Virome Project in the context of a host having its own Virome–like, we have the gut and skin microbiomes, but just singling out the viruses. Is there any (genetic or epi-genetic) evidence of positive or negative selection pressures of viruses on each other, between viruses that commonly cross paths in hosts, but aren’t close enough to “mate” (recombine)?

    Just another chemistry professor, busy throwing it all online this month,

    Love y’all,


    • Jamie Ferguson Jul 15, 2020

      …well, I guess there’s no such thing as virus epigenetics.

  47. Hello Dr Racaniello,

    Thank you & Thanks to Dr. Rich. for all the work and podcasts you do.
    I continue to listen to your podcasts every week. Please bring up your 2013 podcast to top of the lists, so we can listen to Dr. Fauci from then/2013 to now.
    Great questions to Dr. Fauci in your #641 show.
    One follow up Q may be is — whenever Dr.Fauci says – ‘we don’t know’ as a response we may have to ask back – what tests can be done by NIAID to find answers. And, how NIAID is planning to find the unknown. A lot of companies wasting their time & $$s by cleaning door knobs and surfaces, using disinfects, if the risk of transmission is mere less than 0.01%.

    Please keep up the good work!


  48. james m koren Jul 29, 2020

    I have a question. One of the purposes of Phase 3 trials is to find the rare negative side-effects. At some point the rate of rare events will be shown to be smaller than the benefit of the vaccine. At this point will the vaccine be made available to the public? Also, the Russians are effectively doing a Phase 3 trial on their whole population. Can we use this to speed up our trials?

  49. Diana Bahena Jul 29, 2020

    I heard on an episode that you were gonna draft a letter for congress regarding the poitns Michael Mina brought up? Where can I find them?
    Btw – I am a NP and was introduced to your podcast via EMRAP. It has been the best thing I have found this year. You all are doing a wonderful service to the community!

  50. Dear TWIV,
    I am an HIV doc who recently retired as a Professor at UCSF just in time to get sucked back in to work on SARS CoV-2. I am naturally a big fan of TWIV. Since my own research has focused on virus diagnostics I was delighted to hear Dr. Mina’s incisive commentary. I found little to disagree with in what he said during his segment. However, I want to encourage TWIVers to think twice before piling all their apples into the rapid testing cart.

    Point of care rapid tests are ideal for decentralized, low throughput testing and need trained operators on-site. Lateral flow devices are simple and cheap. Antigen detection can be challenging using this format. Even if tests perform well in pre-market evaluations, they often lose specificity in field conditions when problems arise with oral fluid sampling and/or with visual interpretation. Clinicians learn to account for this when interpreting office tests and only use them to manage symptomatic patients. In many risk based or general screening situations (*see below), most positive results could be false positives. If this occurs in testing of schoolchildren, the potential for blowback could be extreme.

    Please don’t get me wrong—I believe deploying candidate devices is an urgent priority, and I am sure rapid tests could be used effectively in ambulatory and primary care diagnostic testing, or in hospital triage. But its not at all clear whether rapid tests can be used to screen asymptomatic schoolchildren. If rapid tests are needed in this situation, all of these problems can be handled: one can decide not to report or act on preliminary positive results; one can use automated readers; and one could use rapid RNA testing devices like the Xpert for same-day confirmatory testing (something that might be practical at a county level). Another solution would be to rely on pooled PCR, which can be incredibly efficient when sample positivity is low. It is worth noting that Labcorp, Quest and other blood bank labs already have the liquid handling and testing machines they would need for pooled testing, many of which are being used right now to handle a crush of individual sample testing.

    All of this to say that on TWIV as in life, there is probably no silver bullet or free lunch—but luckily we live to do the work. Thanks for being the real deal.

    Chris Pilcher, MD

    Prof of Medicine, emeritus
    UCSF and SF General HIV Division

    *PS. Here are some numbers: assume weekly testing of schoolchildren using a test that has sensitivity during an average 7 day detection window, and an optimistic specificity of 99.00% (e.g., in a small field evaluation of 3 candidate oral fluid rapid tests for anti-HCV Ab, all from large manufacturers, specificities were reported of 80%, 93% and 100%.). So:
    If we expect fewer than 1 percent of children to be infected per month, we expect less than 1 in 1000 true positives. With 99.00% specificity, the positive predictive value would be 10 percent.
    In a hotspot with 1 percent of children infected weekly and 1 percent true positives, similar specificity would give results with positive predictive value at the coin-flip level of 50 percent.

    **PPS. I am attaching my own recent JID paper on SARS CoV-2 pooling for interest, which is also relevant. Our estimates agree substantially with Dr. Mina’s.

  51. Bill Kerr Aug 2, 2020

    Recent listener. Love TWIV. Gimme that information dump. Love hearing info not filtered to appeal to the least common denominator in a society that slept through high school science classes.

    I’ve seen a paper passing around by a Oxford zoologist (yes, really) José Lourenço talking about heard immunity for COVID-19 in the human heard, and making some extraordinary claims. While I have not crunched his numbers he makes broad claims that contradict what I have heard and read elsewhere. Would you care to throw some darts at this paper for me?

    Link to paper (unpublished): José Lourenço
    Link to his twitter:

  52. John Wilkinson Aug 2, 2020

    Dear TWiV,
    Michael Mina gave the impression that a lateral flow sars-covid2 antigen test was available today. I found reports on tests under development, but not a fully developed one. Is there a lateral flow or other self-read antigen test that has FDA’s emergency approval?

    Thanks for everything you do. I enjoy the science, and the banter!

  53. Christin Aug 4, 2020

    We’re trying to figure out a safe way to see our grandkids; we’re in Oregon, they’re in Idaho. We can drive in a day and do everything with them outside only. But, where to stay? Is it safe in a hotel with their ventilation system? Do we have our kids ‘wall off’ the upstairs bonus room, but their AC system still comes into that room? Do we rent a free-standing RV and park it in the driveway? Is there a safe way to do this?

  54. Paula K. Barnes Aug 5, 2020

    A colleague recommended I listen to your recent Podcast Episode 647, due in part because you mention CDC’s Emerging Infectious Diseases Journal and it’s art covers. I thoroughly enjoy the art selections and am proud to say that my father’s art appears on the cover of the October 2019 edition. What a clever approach to entice people to pick up the journal to read. I listened to all of the Podcast and while not a virologist I found it very informative. I am now an official fan.

    Thank you very much.

    Paula K. Barnes

  55. Peter Williamson Aug 6, 2020

    Great conversation guys.
    I’m interested in the bio-ethics of vaccination and challenge studies and your complete rejection of the latter. I want to put an ethical conundrum to you and I’d like to know why the risk of that is different to the risk of challenge studies.

    We know roughly 75% of people who get infected with CoV2 are asymptotic or have little more than cold-like symptoms. For those people you might describe this virus as benign.
    We also know that vaccination comes with a small risk of enhanced disease, it does with certain RSV trial vaccines.
    I don’t know if we’ll be able to detect disease enhancement in trials, we might if it affects a large portion of the vaccinated population but maybe not for a subset (say people with a certain genetic predisposition). Would Ph3 studies be powered to detect all potential manifestations of disease enhancement?
    It strikes me that vaccinating the whole population you might actually take a bunch of people who previously might have had a benign infection into the category of more serious enhanced infection.
    How would the risk of causing that sort of harm be different from any potential harm from a challenge study?
    Of course you can do your best to measure the risk of disease enhancement. You can also do your best to measure the potential harm of doing challenge studies on 25-year old healthy volunteers. It seems like both vaccination and challenge studies could fall into the Fauci category of “perfect being the enemy of good”. Why outright dismiss one?
    Keep it up
    Pete, Ottawa, Canada

    • profvrr Aug 7, 2020

      One answer: COVID-19 kills. Who will take responsibility for those who die, or are permanently disabled? 20% of infections are serious, not a small number. And a challenge is not needed – there are plenty of cases at the moment. That’s why we dismiss this one categorically.