Katy writes:

Hi TWIV team, 

I’m 6 months pregnant, and while I know that the data so far do not show an increased risk of serious disease in pregnant women, a recent visit to my OB brought up a different concern for me. 

She said that if I were to test positive for SARS-CoV-2 when I am in labor, they would need to take my new baby away for 2 weeks to prevent me from infecting him. This is obviously a horrifying thought for a mom (although part of me thinks, how amazing would those 2 more weeks of solid sleep be?!). 

But in all seriousness, would this practice be justified? Have there still been no deaths in kids under 9 years old? Are infants at great risk for serious (if not deadly) disease? What do the data say so far? 

Of course if this happens to me and there’s a real reason to quarantine my baby away from me, I will go along with it. But if there’s no solid data behind it, I would definitely want to fight this recommendation. 

Thanks as always for providing such reliable information and thought-provoking critical analysis in this time. 

Katy J.

Anonymous writes:

I am currently two months pregnant (bad timing I know). There does not seem to be any definitive guidance on the possible impact of COVID-19 on pregnancy, especially during the first trimester (some limited information on the CDC website). Any insight you can provide based on other coronaviruses?  Right now I am taking all the recommended precautions and letting my partner do the grocery runs and plan to do my pre-natal appointments via telemedicine. 

Follow-up, will there be a baby boom in nine months? Generation name suggestion: coronials. 

Thank you,

Prefer to Remain Anonymous 

Jason writes:

I am a 45 year old relatively healthy male with high blood pressure for which I take an ACE inhibitor. There was much talk early on how these medications could be detrimental if I was infected with Covid-19 from China. My doctor refuses to change my medication. Is there any update on the connection between ACE inhibitors and Covid-19 ? Is this a battle I should fight with my doctor?

Thank you for all you do. 


Iah writes: (pronounced Eye-ah)

Hi TWiV gang! 

Firstly, I am so grateful that you are doing extra episodes, with a variety of specialist guests – it really helps to keep my mind on track whilst working from home! I’m an out-of-action research assistant (mosquito/arboviral genomics) based in Melbourne, but I used to work as a technician on a MERS-CoV transcriptomics/proteomics project at the University of Bristol, UK up until December last year – what a time to switch topic! 

Anyway, my question for you all is regarding a video that has been circulating over the last few days by a clinician claiming that use of ventilators for COVID-19 patients might actually be doing more damage that good: https://nypost.com/2020/04/06/nyc-doctor-says-coronavirus-ventilator-settings-are-too-high/

Forgive me for using NY Post as a source, but it was the only article I could find, and it summarises what he says in the video quite well, to save you the time of watching it.

I wondered if, perhaps when Daniel Griffin is back on the show, if you could explain what the science is behind using ventilators, and whether the other doctor in the video has a point about ventilator use usually being for people who’s muscles are too weak to breathe, rather than viral pneumonia?

I had the video sent to me by family (I am inundated, being the family virologist) and I said I would ask some real experts! 

Thank you all for your incredible service to the cause, stay safe and healthy – we need you!

Best wishes 

I’ah (pronounced Eye-ah)

Suellen writes:

Guys, just listened to TWIV 599, and I was surprised to realize that you all have never watched The Zoo on Animal Planet. It’s a reality show that gives us a behind the scenes view of life at the Bronx Zoo. Best freakin’ show on television! If you did watch, you’d have seen how they handle the big cats. Lots of positive reinforcement training goes on, but of course (like you said on the show) the keepers do maintain a safe distance and there is always a barrier between them and the tigers.

I suspect that they may have been able to use their extensive training of the tigers to get the sample they needed, but if not then, yes, they would have had to sedate the big cat.

Paul Callie appears on the show from time to time. It’s a great show, full of very useful information about the zoo and what it takes to keep it running. 

You can stream it online too: The Zoo | Watch Full Episodes & More! – Animal Planet 

Love the show (but you know that, right?) Maybe you can get yourselves a reality show on the making of the TWIX podcasts — LOL. 

Keep up the great work. An aside, I’m working my way back through Immune episodes for the THIRD time (I learn so much from those podcasts!) and managing to keep up with TWIV and its siblings as well.

Weather here in the ATL — as Rich says, “sunny with a chance of COVID-19”


Sam writes:


Loved the way Rich’s questions (like the Pips) served to highlight Jon’s  talk (he was Gladys Knight). Some bits were a bit too technical for me but I stayed engaged because Jon was so damn enthusiastic.


Jillian writes:

Thank you for your wonderful show.

Re hepa filters

They don’t all contain fibreglass but many do. Those with fibreglass aren’t suitable for making face masks with. You could inhale the particles and although they are less harmful than asbestos they can cause irritation, damage your lungs and may be carcinogenic. Don’t cut them up and don’t breathe through them unless they’re specifically made for that purpose. I’d suggest homemade masks should just be made with cloth instead. Hope this helps!


Regula writes:

Dear TwiV,

thanks so much for the comprehensive information that you guys are putting out there week after week. Like you, I can’t wait to hear future TwiVs about viruses other than Corona again, but for now I am very grateful for the valuable information you are putting out there.

With regards to Rich’s blog post about there being no data whatsoever on the true infection rates, this has changed since today.

A large scale serological and virological study is currently being conducted on the general population of Heinsberg, Germany, which is one of the earliest affected municipalities in the Northrhine Westphalia region of Germany. The only published data is currently in the form of a pdf published by researchers from the university clinic of Bonn, Germany, where they stated preliminary results of an infection rate of around 15% (from ca. 500 samples).

If true, this data would translate into approximately 38’000 infected individuals in the municipality (while targeted PCR testing found 1486 positive cases), which would put the mortality rate in the ballpark of 0.4%.

It is still relatively early in the study and solid results still have yet to be published, but I thought you’d find it interesting nonetheless.

Just to provide a source, I am attaching the pdf of the official statement and a short video from the German WDR television station, even though you probably have not much use for it since it’s all in German :).

Keep up the good work!


Sophie writes:

Dear TWIV,

I am a student in Bi 115 (Virology) at Caltech, and we recently discussed the bat immune system. One thing that I found quite interesting was that bats have to suppress their immune response due to the inflammation caused by their high metabolic activity. Could people with higher metabolism (which I believe is associated with exercise) also have increased inflammation that could lead them to have a suppressed immune system that would allow them to tolerate the virus in a similar manner as to bats? 

Thank you,


Jake writes:

Thanks for your great work and podcast! 

You all recently discussed whether the vaccine industry could pre-manufacture vaccine while doing safety and efficacy studies, and also discussed the problem of scale to produce sufficient quantities of an mRNA vaccine. Here is an interesting news item that touches on both: 


It suggests Pfizer and partners are scaling up “at risk” to produce millions of doses by year end while the approval process is underway. 

Bernhard writes:

I am a microbiologist working for a contract research company in Vienna (Austria) performing non-clinical studies investigating the production processes of pharmaceutical companies for their capacity to remove or inactivate potential viral contaminants. As such, many of my friends ask me about my opinion on the current SARS-CoV-2 pandemic, wherefore I am trying to inform myself as much possible about that topic in order to provide valid information to people having little or no knowledge of viruses. Hence, I am very thankful for your work on TWiV, you are a great source of information (plus an extra thanks to Rich Condit for stating temperatures in Celsius, too).

Looking at the hygiene rules made public by governments around the world, which often focus on coughing and sneezing into one’s elbow (as well as social distancing, hand washing etc., of course), it seems odd to me that talking and breathing are almost always ignored as potential routes for transmission of respiratory diseases. I found two papers by Asadi et al. (Aerosol emission and superemission during human speech increase with voice loudness, 2019; Effect of voicing and articulation manner on aerosol particle emission during human speech, 2020), in which they argue that talking, especially loud and using many vocals, can result in aerosol generation comparable to coughing or sneezing over time, especially since talking is typically performed more frequently than coughing or sneezing. Therefore, I would welcome, if hygiene rules publicized by governments would include not talking into someone’s face from the top of one’s lung or stop singing while passing by somebody, especially in confined spaces. Maybe you can help disseminating this information to the general public. Thanks!

With best regards,

Bernhard Samminger

Gage writes:

Hello TWIV team! 

Long time listener, first-time writer. First I just want to say thank you for all that you guys do, you are my first stop for all things viruses and as a prospective Ph.D. student looking to study viruses/astrobiology this podcast (as well as Vincent’s YouTube lectures on his virology course) is invaluable to me. 

I am sure you all are aware of the website ViralZone.org but I was just on their site and found a very interesting page on how the different SARS-CoV-2 antivirals work to potentially inhibit the virus, in graphic format. https://viralzone.expasy.org/9078 I am a visual learner so this was very eye-opening to see an overview of how these drugs work. 

Here in North Texas, it is a warm 24C and nice and sunny out!

Stay safe and healthy everyone! 


David Spector writes:

Dear Twivniks,

First of all, let me congratulate all of you, and especially Vincent, for a Herculean job as you track the unfolding of the pandemic.  You have now become “must hear” for anyone who really wants to understand what we know and what we don’t know about this virus, the disease it causes, and attempts to manage it.  I promote TWiV every chance I get and was pleased to learn early on that my children are now devoted fans. Neither is a biologist. 

Today I read an opinion piece in the NY Times by Ross Douthat, with whom I usually disagree but mostly find well-reasoned.  Unfortunately, in this case he makes the mistake of writing about a subject he appears to know nothing about, the nature of scientific expertise.  Infrequently I read the comments section in the Times to see how people react to a particular opinion piece. I’m glad I did this time because I came across this entry:.   

If you define “experts” as people with reliable, tested solutions, then COVID19 has no experts.

But if you listen to the virologists on This Week in Virology podcast it will restore your faith in experts, and in humanity.

There are folks who have studied viruses long before and now during COVID19. For them, this virus is just another in a long line of DNA/RNA actors.

They get into depth, and it takes an hour each episode [my note: that’s being kind], which is beyond the attention span of most listeners, certainly of most journalists, but it’s there for those who care to learn.

In particular, their guest, Dr. Daniel Griffin, elucidates how physicians have learned from their mistakes to treat the COVID19 patients more successfully.

As I remarked to a colleague recently, we are all becoming virologists now.  She replied that were we able to still have cocktail parties, those of us who used to stand in the corner of the room would now be the center of attention.

Stay safe and keep on twivvin”.


David J. Spector, Ph. D

Professor Emeritus of Microbiology and Immunology

Penn State Hershey

Cameron writes:

To the whole team: 

This real estate attorney in Phoenix loves the show.  Two questions:

1.       If it’s possible to get herd immunity to a coronavirus, why don’t we have such immunity to the common coronaviruses that cause common colds?  

2.       How much has your audience increased over, say, a year ago?   This is your fifteen minutes of fame—use it wisely! 

[vr: we are not famous: there are still comedy/politics pods that get 1.5 million downs per episode. But we will not change our goal of educating people about viruses]

John writes:

Hi TWIV Hosts,  

I am just an ID MD from Brooklyn.  

Regarding an approach to a SARSCOV2 vaccine, Jon Yewdell sounded optimistic that a nucleic acid vaccine would work.  

I have read that this technology has shown promise with Zika.    

It just seems hard to believe that RNA injected into skeletal muscle would:

1 survive

2 be picked up by tissue macrophages

3 be translated 

4 be carried to a regional lymph node and presented on MHC to CD4 cells

I wonder whether creating virus like particles – ie like with the HPV vaccine – or an old school inactivated/killed viral vaccine would be a better approach.  Or live attenuated ie measles or varicella.  

Can you guys rap about vaccine theory…  

John DeLury MD 

SUNY Downstate

David writes:

so much appreciate TWIV. I have no science background, even from high school, but I am auditing Virology 2020 on You Tube. In lesson 1, Vincent talked about the danger of seeing virus from human terms of intention, etc. 

I am interested in your perspective in all the war terms used to talk about Covid-19?

I have started lesson 2 in Virology 2020, very slow going because I bounce back and forth between the course and the podcast. 

Thank you for all the work you are doing and information you are providing. 


Here is a little poem about my experience with one slide in lesson 2:

Cellular Reception

Out of my comfort zone

lifelong learning meets danger, even death,

I study Vincent Racaniello’s

Virology 2020, Lecture #2

The Infection Cycle.

Vince from NYC’s Columbia

outlines important definitions –

it will be on the exam, he warns.

But auditing the course on YouTube

makes me immune

from the exam ——- not the virus.

Resistant cells have no reception

Susceptible cells are necessary but not sufficient

Permissive cells are necessary but not sufficient

Infection troubles multiply

when susceptible is also permissive

and replication exceeds sufficiency

at human costs beyond my comprehension.

Disney World shut down but that doesn’t


our world from being

a small, small, world.

Elco writes:

Dear TWIV team,

I thank you for your excellent podcasts from a SARS-CoV2 beleaguered Milan.

Please read the document I enclose, which summarizes some thoughts I co-wrote down with a few colleagues.

I believe the scientific community may have been slightly myopic by focusing on viral isolates from patients only.

If attenuated SARS-CoV2 were to be out there, wouldn’t that be important to know?

My question would be if you endorse the concepts that we put forward & if so whether you would be willing to act as co-authors on the piece to underline your endorsement. We feel it should be submitted ASAP!

Regardless of what you may think of our document I wish you all the best with TWIV!

Stay well

with regards,

Eelco van Anken, San Raffaele University, Milan Italy

[vr: he wants to look in asymptomatic people for attenuated viruses. But asymptomatic is probably a host response, not virus differences]

Bert Rima writes:

Hi Vincent and all TWIVers 

In TWIV 598 and in some of the previous podcasts you have questioned whether there are any studies that indicate that a higher virus dose could affect the outcome of a virus disease in humans. This made me think back to the studies that were done on the fatality of measles and especially on the high fatalities in some countries in the 1980s. These studies became relevant when we were asked to evaluate the potential side effects and excess mortality associated with a high titre measles vaccine that WHO wanted to introduce to close the window between the waning of maternal antibodies and the high levels of circulating virus. There were several countries in West Africa and Haiti which had very high levels of measles mortality on the 12-20% range. 

In one of the studies published in the Journal of Infectious Disease [M Garenne and P Aaby: Patterns of exposure and measles mortality in Senegal JID161(6) 1088-94] there was a clear indication that dose may affect outcome. Several of the other studies we evaluated had the same indications i.e. that index cases in a household which probably acquired the infection from the community had a 3 to 6 fold lower mortality associated with them than secondary and tertiary cases in the household. This was interpreted by us as indicative of a dose effect at the time. It is of course not an experiment but an epidemiological observation, which suggests that like in animal experiments dose matters for human infections. I think this question could be of importance in how we look at the Covid-19 epidemic.  It may well be that community circulation and transmission of low doses of virus in these settings would affect the outcome for the infected person as mild or asymptomatic. I think specifically of the data you mentioned that showed that in Hong Kong (and I think the same is observed in Singapore) that most of the cases that have been identified (probably the most severe ones) were acquired in household settings. Anyway, better not to speculate further until such times that we have proper data on the prevalence of antibody responses. But it may be a thought for the modellers.

Keep up all the good work.

Bert Rima 

Chris Upton writes:

Re: Yewdell TWiV

This is my favorite of all time.

I love the way Jon says “I don’t know”, “we don’t know” so many times….  It’s a real reflection of how science is.

The talk touched on so many mysteries and subtle topics of virology and immunology.

The goal of every science student should be to learn enough to understand all the material that he was talking about.



Yvette writes:

a family friend recently sent me video of people claiming the virus does not exist and that the deaths and sickness we are seeing are related to the installation of 5g towers. I thought it was an isolated incident. So I told them what I know to be true .

Recently, I found out this is a more widespread thought and that towers and engineers have been harmed internationally because of these thoughts and sentiments.

Here are two maps:

  1. one that shows were 5G towers currently exist: https://www.digitaltrends.com/mobile/5g-availability-map/
  2. one that shows where COVID19 infection clusters are: https://hgis.uw.edu/virus/

There are clusters close to some of the tower locations but there also exist clusters where there are no towers. please Discuss this.





Graduate Research Assistant 

University of Maryland | Plant Virology Laboratory

Joel writes:

This weekend Stanford (I believe the Health Policy department, PI: Eran Bendavid) conducted a survey of 2500 households (I’m actually unsure of the N, except from the news, my wife and son got a slot and their participant ID was over 6000) to try to determine seroprevalence of SARS-CoV-2 antibodies in Santa Clara County. 

I would estimate that the seroprevalence is going to surprise on the upside (especially given that participant selection is problematic fact that tests have been rationed and a large amount of participants will be like my wife who was presumed positive with mild symptoms based on exposure and signed up simply to figure out if she’s actually immune). 

I hope that leaders and the public interpret the—likely dramatically—revised case fatality rate appropriately (in the context of acute care capacity).


Best Regards,