Clay writes:

Dear Vincent and TWIV team,

Keep up the amazing work.  What a terrific asset to have such smart people focusing energies on understanding and communicating the latest science (with all of its imperfections and uncertainties).

I’m a practicing internist in Washington, DC and have a patient whose disease course scares me – as the implications are potentially massive.  It would be great if you could pose this question to Daniel Griffin tomorrow on your show.

I have a 54yo male patient who had mild COVID (cough and sore throat) with positive PCR test on April 4th.  He recovered quickly, had two negative PCRs in the subsequent weeks.  He never got an antibody test.

He presumed he was immune, however, and when his son contracted COVID-19 in mid-June, they did not distance themselves.  On June 22nd, my patient developed fever and cough and the following week he got tested for COVID-19 and tested positive.  His symptoms have become increasingly severe (including O2 sat of 88) and fever of 103.  He is on his way to the hospital now as I type this email. 

Here is my question and concern: if we believe the story (and I have no reason to believe the PCR test in April was a false positive), this appears to be a perhaps Dengue-like worsening clinical syndrome upon reinfection.  Are you seeing any cases like this in NY, and, if so, do you believe that these are rare one-offs, or could they have greater implications for the safety of vaccines or even the ability to develop natural herd immunity?

Thanks again and all the best,


Tim writes:

Dear TWIV Crew,

I always enjoy your podcast and each episode is an engaging learning experience for me.  It’s a balmy Sunday night here in Madison Wisconsin at 76F or 24C depending on your preference.

I’m a school administrator and not an expert by any measure. With SARS-CoV2 being so new, we lack clear signposts about how to plan for the upcoming school year.  We were closed for all but remote learning this spring after mid-March and this emergency remote learning had many shortcomings academically, as well as negatively affecting the social and emotional well being of  many students. It also placed hardships on parents and guardians who were essential workers or working from home. My apologies if you have already delved into this topic already and I have missed it, but I am hoping you can explore the state of our current understanding of SARS-CoV2 transmission in children and adolescents.

The American Academy of Pediatrics in its Return to School Considerations takes a strong position in favor of children learning in person on campus. “The AAP strongly advocates that all policy considerations for the coming school year should start with a goal of having students physically present in school…Although children and adolescents play a major role in amplifying influenza outbreaks, to date, this does not appear to be the case with SARS-CoV-2. Although many questions remain, the preponderance of evidence indicates that children and adolescents are less likely to be symptomatic and less likely to have severe disease resulting from SARS-CoV-2 infection. In addition, children may be less likely to become infected and to spread infection.

I have a strong respect for the AAP and over my career have found their guidance helpful, grounded in evidence, and child-centered. I share the strong desire to have children in school if the risks can be safely managed, but the strength of their characterization of the evidence on transmission surprised me as I have felt up to now that there is much we do not know and the reality that schools have been mostly closed during the epidemic likely has inhibited traditional epidemiological studies to date. The recent STAT article on the puzzle we find ourselves matches my sentiments better, but I am not a scientist nor a health care professional. I also likely put more weight in pre-prints and preliminary research letters like the recent Korean study on mildly symptomatic and asymptomatic children than I should. When you are looking for evidence to guide decision making, it’s tempting to be quick rather than patient.

In the end we’ll follow the direction of our local public health department (no statewide COVID policy architecture anymore due to our state’s Supreme Court, but that’s a separate matter), yet in our coordinating calls I can tell they too are navigating with incomplete evidence when it comes to children and transmission. I know there are probably no clear answers, but your discussion of where our understanding sits right now would be very interesting to me.

Thank you again for your truly outstanding and informative podcast.

And a final observation as I’ve caught up on episodes and know now that you have fielded some related letters, is that I’ve noticed some work on social networks among different age cohorts of children and adolescents and how that might contribution to mixing and transmission of influenza.  Specifically, Glass and Glass seem to suggest not only that high school age students have wider networks and so greater assortative mixing compared to younger children, but perhaps may have a higher potential for super spreaders (Figure 5 e).

This may help explain why younger children in particular may be lower risks for spreading SARS-Co2 despite evidence that they can shed adequate viable virus for transmission.

Best regards,


Josh writes:

Hello TWiVers,

I’m “only” an Engineer and have been listening to your podcast since March, 2020.

I’m listening to 634 and the discussion around the G4 influenza strain found in pig surveillance.

My first question is: Is it possible to tailor a vaccine or a vaccination strategy in pigs to direct the genetic drift away from efficient reproduction in humans or efficient between humans?

Seems like stopping the next zoonotic origin pandemic in the original host before crossing over to humans would be optimal. I assume that implementing this would be much easier to do in farmed pigs rather than bats.

Are influenza strains that are optimized for transmission in pigs necessarily less optimized for infecting humans? I would guess not, but I wonder if it is possible to “outcompete” a swine influenza with a less deadly but more transmissible strain that results in an immunity to the strains that can jump to humans.

The temperature here in Rochester, NY this morning is 76°F with 63% humidity and an effective reproductive rate of 1.00 according to

Many thanks for all you do,


Mike writes:

Hi TWIV’ers.  It’s 551 degrees Rankine here in South Florida.  Your reporting was a bit out of date. Airline rules vary by the airline, but mask wearing enforcement has stepped up across most airlines.   Here are the rules at my airline as I understand them:

All customers must wear masks at all times on the aircraft unless eating/drinking.  My airline will warn you once if you take your mask off. If you continue to not wear a mask we will put you on a list of people who are not allowed to fly.  You are correct, it’s impossible to enforce the rule on a particular flight (an escalation to a physical altercation on the flight is probably less safe than someone willfully disobeying the mask requirement), but we will not let a person who will not comply with mask requirements fly again on the airline.

Only SOME airlines are selling full airplanes (currently United and American).  Other airlines such as Delta and Jetblue are still leaving open seats to help with physical distancing.  All airlines are continuing to evaluate this and it might change in the future.

Airplanes have some of the best air circulation you might encounter.  Generally the airflow is from your head towards your feet.  Most of the air is fresh air from outside the plane (this air is heated up to around 200 celsius due to compression before being cooled and introduced to the cabin.  The recirculated air is passed through HEPA filtration (99.97% of .3 micron particles) before coming back into the cabin.  According to the EPA, the .3 micron particle size is the WORST CASE scenario.  Larger and smaller particles are filtered even more efficiently.  Reference:


(I’m a Captain on the A320 aircraft at Jetblue.  I am speaking for myself and not on behalf of my employer)

Jenelle writes:

Hi all, 

Love the show, only found it this year – my background is in maths and physical science. For some reason I’ve discovered a need to catch up on microbiology this year and have been an avid listener over the last few months. 

I finally have something I can be pedantic about.  In TWIV 631, someone (Rich I think) said that Canada follows the Queen of England. They don’t, the head of state of Canada is the Queen of Canada, just like the head of state of my country is the Queen of Australia. It’s just that these roles happen to be held by someone who also happens to be the Queen of Great Britain. Each country has its own copy of the Act of Succession, but at the moment they are identical, so each crown follows to the same person. 

I currently work for the Australian Parliament and it’s something people can get picky about at my workplace. We aren’t led by the Queen of England and Canada isn’t either. 


Bradon writes:

Dear TWiV Team,

I’m a new listener, thanks to Ginger from Brain Science recommending you in response to the pandemic.

In your episode 629, I caught a reference to a Zimbabwean population, and your surprise over the median age of people in the data set. I’m Zimbabwean, and still resident here. 

Firstly, it’s exceptionally hard to get accurate statistics, because of several factors including a lack of canvassing/census data, technology, and integrity among politicians and civil servants. (For example, I’m trying to collect a data set to do chaos analysis on, and even funeral homes and life insurance companies aren’t responding to my queries for longitudinal death rate data.) 

Secondly, yes, we do have a very low life expectancy here. At the ripe, old age of 36, I’ve long exceeded average life expectancy. Factors include HIV/AIDS infection and lack of treatment, political violence, and high rates of traffic accidents.

Thank you for keeping me informed with the latest on SARS-CoV2!



Michael writes:

Dear Professor Racaniello

Politics in virology.

There may never have been a better example in human history than the role a country’s politics and its political economic ideologies play in the spread of an epidemic and a pandemic than what is going on in The United States right now. 

A country’s political system should be an integral part of the modelling data used to project the spread of infectious disease.

It’s a sad and dangerous precedent being set by the Republicans and Capitalists that assumes science and politics do not affect each other. While there is no scientific data to support my assertion I think it obvious a study would bear out my hypothesis.



Alex writes:

Hello Vincent et al.

The following study points to a relatively tiny benefit to fairly large scale testing for Sars Cov 2, when compared to other public health interventions.



 in Enterprise Ontario, at 30 Celcius

Vr: well duh, they are only testing 5% of the population each week. Of course that won’t work! You have to test everyone weekly!! Not possible? What the hell did you do during the lockdown? 

Robert writes:

A retired country doctor’s perspective

Dear Dr. Racaniello and TWIV crew:

I’m a retired Family Medicine physician, within a few months of the same age as Dr. Racaniello.  I “discovered” your podcasts a couple of months ago at the beginning of the current pandemic, when it became a patriotic act to stay home, which I have been doing.

In early February I told a group of friends that this would be a Big Deal, and they all thought I was nuts.  Several have apologized to me since then for my predictions of doom.  My family listened, however, and prepared for problems, as did I.  I recently donated blood and was tested for antibodies for which I was negative.

Please allow me to opine on several comments from the most recent posting, TWIV 632 and other things.

1.  Of course I have all the time in the world.  I listen to your podcasts daily, TWIV, TWIM, TWEVO, TWIP.  I walk my dog several times a day, farther than she and I need to do her business, which is good for us and allows me time to listen to your podcasts. They are most entertaining.  I love the banter among friends.  I love the puns.  Please keep it up.  I have to admit I’m somewhat afraid to go the the gym where nobody but me and the staff wear masks.  I’m certain I’m the only one who breathes hard …

2. I agree politicians should not opine on science, especially those who claim to lead this country, who don’t listen to their advisors.

3. I have often told folks that I am not a scientist, I’m a technician with scientific training.  I have tried to keep up over the years, especially evidence based medicine, which I will agree with Dr. Griffin was often opposed by the old guys when I was in training in the 70s.

4. Your correspondents mentioned death rates in several countries, like Iceland, where the death rate was low allegedly due to the low carb diet.  This is an imprecise use of the term “death rate”.  The death rate overall is 1.  With the exception of a few believers in specific religions, nobody gets out of this world alive.  If you don’t die from heart disease you will eventually die from something else.  It was pointed out to me that although a third of people who smoke die from tobacco related illness, the other two thirds die from something else.  This is not cynical, this is fact.  When one cites death statistics one should, if claiming to be “scientific”, be specific about what one means. Do you mean excess deaths, and compared to what and at what ages? If you want to be pedantic, which I have been all of my life, you have to be specific.

Thank you for your tremendous podcasts.

Robert B. McCown, M.D

Bill writes:

Dear Vincent and all,

This is a different, perhaps easier to read version of a previous email I sent.  

It is 21 degrees C, clear and sunny here in Vancouver this afternoon.

In British Columbia, we have done well to control the spread. We have had 148 deaths in a population of about 5 million.
Here are a few of the things we have done. The border with the U.S. is closed. We have enough tests that anyone who wants one can get one. We have locked things down quite a bit. We have a well-running comprehensive program to isolate all who test positive and to trace the contacts of all positive cases.  
We are averaging about 20 newly diagnosed cases a day — and this is declining.  Today we have 8 newly diagnosed cases in the province. Our ICUs never reached even 50% capacity.  
Here is a link to some interactive graphs and charts re the course of the disease in Canada: … -1.5510000.
The single key thing the provincial government did well was put the Medical Health Officer in charge of the pandemic response. The government then energetically followed her lead.Here is a link to an article about this: … 609802a49/
The other key thing we mostly all did as citizens were to take seriously our responsibility to protect ourselves and our fellow citizens.
Thanks for your great work on this!  I hope you continue to have content re outbreak management — like your series of letters re Sweden and Taiwan.
Ks: A Canadian friend sent me this; similar content

Debbie writes:

a wonderful professor passed along your podcast —

thank you for what you do!

here is a covid-19/antibody/contagion question.

a loved one fell ill for two weeks. severe headaches, fatigue, loss of taste/smell. teleconference doc said yes to covid-19 as diagnosis. about 2 weeks in, got the swab, but that proved negative (faulty test?). this week, antibody test showed two antibodies — short & long term were indeed detected. 

question: at this juncture, would this individual still be susceptible to catching covid-19? could this individual carry the virus, & pass it on? 

or — is there any evidence to suggest that because of the presence of antibodies, this individual has some immunity & therefore cannot pass the virus along to others? 

hope this makes some sense!

– Debbie

Marc writes:


Can you set the record straight that there is almost zero chance of being infected by a fleeting biker or runner or even walker passing by outside on the street or in a park?  It is just awful watching people scurry to a side or angrily glare out at you out of mass hysteria induced by politicians and the media. You’re not contracting coronavirus outdoors in low density settings. Buses, subways, crowds, sure that’s a different story, but a beach on a sunny, humid day? It’s zero.  Let’s restore at least a modicum of sanity.





Marc Garrett

Chief Operating Officer

Quality King Distributors, Inc

Todd writes:

Hi team!

Is the “Multisystem Inflammatory Syndrome in Children” mentioned in the article ( a cytokine storm or is it something related or is it something new/rare?


John writes:

Love the show….this is a fascinating narrative of flying back to China with lots of pictures and details.



Alina writes:

Hi — I love TWIV and listen to every episode now, no matter how long and no matter whether it’s about SARS-COV2 and covid-19 or anything else.  Thanks for all the amazing info.  I work in public policy for a Canadian province’s ministry of health. For years, we (like other health planners) have been obsessed with the impact of an aging population on our health care systems. Lately, I’ve been wondering what the probability is that this pandemic could radically reshape the population age profiles of western countries. What do you guys think?

Thanks, and keep making nerd-dom great again,


Michelle writes:

Hi all,

 All I want to say is that I absolutely love your podcasts….all of them. I love the science, the humanity…I feel you are all my best friends despite never meeting you.

You are the silver lining in all of this…knowing that there are honest, intelligent, unassuming folks like you in the world is tremendously reassuring.


(Physician and musician in NYC)

Felicia writes:

What if…

What if the whole world agreed to stop everything for just two weeks?
We could beat this virus down to zero.
What if we all agreed on August 1st – 14th as a two-week period of complete household isolation ahead of time so we could plan for it?
We could beat this virus down to zero.
What if we all stocked up on food for two weeks and shut down even grocery stores?
We could beat this virus down to zero.
What if we could provide food and isolation housing in hotels and dorms to truly essential healthcare workers, emergency medical technicians, water purification and sanitization workers, electricity workers, firefighters, and homeless people for this two-weeks?
We could beat this virus down to zero.
People would stop dying of covid-19.
The economy could swing back fully, instead of a weak pendulum of reopening and reclosing.
We’d save billions of taxpayer dollars.
Grandparents could hug their grandchildren again safely.
People could date again safely.
We could go back to work.
We could go back to school.
We could go back to sports and concerts.
We could make this madness go away.

Best regards,


Professor of Chemistry

Virginia Tech

Jesse writes:

Good morning,

Listening to TWIV this morning I heard several comments relating to the surge of cases in the 20-40 age group. While a lot of this may be due to people in this age group patronizing bars as they re-open, it is important to remember that these cases may be the result of choices these individuals make on their own. 

It is important to remember that this age cohort is vastly overrepresented within the front line of many service industries. As restaurant and bar closure restrictions fall away in the rush to “restart the economy” these workers are then ineligible for continuing unemployment benefits. These people have no choice but to return to work and expose themselves to unmasked populations (can’t wear a mask while you are eating in a restaurant). Of course the clientele opting for dine-in service may be within the same age cohort, but it seems likely that the customers are predominantly older and of a more comfortable socioeconomic position.

I really enjoy listening to TWIV but please don’t shame an entire population based on anecdotal reports and encourage your listeners to support local restaurants with takeout (and still leave a tip!) whenever they can.

Take care,

Jesse L.

PS not a server but have been in the past

Barry writes:


I will TRY to make this short though please know that my admiration for your information and efforts is deserving of many pages of praise that I leave to others with a more poetic bent than I.

I know that what I am about to posit is nothing less than heresy but here goes…could the virus be mutating, BUT only in limited, special, highly constrained situations?

In Victoria, Australia, we are the last state to have SARS COV2 in community transmission and we are having outbreaks now.  We had the hardest and longest lock downs compared to the other states but yet we still have transmission and outbreaks seemingly from asymptomatic carriers.  Virtually no-one in Australia wears a mask, anywhere, except health care workers at hospitals.  We seem to rely heavily on our TETRIS to do the heavy lifting in keeping us safe from outbreaks.  Most people get tested when symptomatic.  In Victoria we also genome sequence the virus from 75% of positive test results which helps track where spread and outbreaks have come from, even when geographically distant and seemingly unconnected.  There will be a documentary about this one day I’m sure…

Under these conditions where the virus is not barred from transmission by it’s host wearing a mask, and only virus that presents as symptomatic disease is quickly nipped in the bud through TETRIS, do you agree there may be some small selection pressure on the virus to present with less severe symptoms?  If you agree then the question is one of time – how long is long enough to see the virus become milder?

Perhaps, with the genome sequences in hand, which they are, one could correlate different strains of the virus with different severity of disease.  I expect I will not like how little difference it makes but maybe not.



Tim writes:

Hi TWiVers:

I just read the Washington Post article:

Coronavirus autopsies: A story of 38 brains, 87 lungs and 42 hearts

It was incredibly intriguing to relate the Dengue Fever discussions and discoveries from #633 to the comments in the Post article.

To the point where I wondered if TWiV has been ordering the sequence of some of these shows to help us understand where some solutions may ultimately be coming from.

Or just the fortuitous effects of knowledgeable experts.

Anyway, I am beginning to believe a whole lot of the broader journalist pools need to make you regular listening.

I would also be interested in your observations on the effects of the changes in communications channels and processes as a result of the pandemic.  You all seem very comfortable with the plethora of unanswered questions you face daily.  I think we all need to develop better acceptance of those uncertainties and risks.

Saul writes:

It’s no big deal for me to wear my mask properly. And I often nudge other people to wear their masks over their nose. But I am wondering if I might leave them alone. Especially in situations where they might be sitting more than 2m away or outside. What’s your learned approach?



PS I am a recent listener… While much goes over my head, I benefit immensely from the rest. Thank you! (May the virus go over our head as well.)

Fred writes:


I have a couple of thoughts around masks. 

I see quite a lot of people that don’t seem to know how to properly wear a mask. They push it under their chin, or let it hang on one of their ears or just take it on and off whenever they need to eat/drink/talk(!)…

How does this affect the protection against the virus? I guess the risk is mainly that you will risk to infect yourself, rather than other, so is it a case of “you only have yourself to blame?”

And how much does it differ between homemade and “real” masks? 

And what about us that have a hard time wearing a mask? Is it enough that a majority wear it? Or should we have to stay away from people until the vaccine is here? 

One friend suggested that I could wear a hat like the beekeepers have, would that be enough to protect others?

And if you have antibodies, would you still need a mask? 

Bing writes:

My lament today is only indirectly about virology.  So let me get my virology lament out of the way first.  When the “War on Cancer” began, I was a much younger mathematical analyst in the FDA.  Even from that sideline, I could see that the disastrous insistence on massive searches for chemotherapies was suppressing resources needed for more basic science.  Viruses routinely rewrite our DNA. Too many years late, we discover that viruses cause cervical cancer, and we develop a vaccine.  Of course, virology and immunology hold the real keys to controlling cancer.  But those bids for increased support fell on deaf ears.  Okay, here’s today’s lament.  The inconsistent bases on which Covid-19 testing is occurring makes it almost impossible to interpret the large-scale data.  There is no plan to use even 5% of the capacity in a statistically meaningful way.  That would be more than enough to get an accurate handle of the real prevalence, spread, and consequences of Covid-19.  But the current behavior of seeking and getting testing is almost impossible to model.  The brilliant work of Seattle/King County health department, Mass General Hospital, and a few others I don’t know about  will be our only hope to learn what we need to learn from population studies.

Bing Garthright (pub’d as Wallace E. Garthright, Ph.D.), retired Biostatistician from FDA/CFSAN

Dimitar writes:

Dear Prof. Racaniello et al.,

Thank you for the effort and goodwill to publicize your invaluable expertise and most of all demonstrate how scientific thinking works through exciting discussions captured on a variety of high-quality podcasts.

Yesterday I stumbled upon an announcement by a UK government official which I find quite peculiar even for politicians who have made a profession out of the habit to overpromise.

Here’s a transcript of what Alok Sharma, the UK Business Secretary, said during the Sunday COVID-19 UK Government briefing, as quoted by SkyNews and accompanied by the video footage of him saying it to verify the validity of the source (

“This new money [£84m] will help mass-produce the Oxford vaccine so that if current trials are successful we have dosages to start vaccinating the UK population straight away.” 

“This means that if the vaccine is successful AstraZeneca will work to make 30 million doses available by September for the UK as part of an agreement for over 100 million doses in total.” 

Could you please evaluate this statement as scientists who have insight into vaccine development? How realistic is it to develop from scratch a working vaccine in such a short time and to plan to vaccinate 30 million people with it? What could go wrong?

Thank you for your time and consideration.

Keep up the great work!

Kind regards,