Christiane Wobus writes:

My take on this question is that bacteria promote but are not absolutely required for virus infection. GF mice have M cells and our data in vitro shows that MNV can be transcytosed by M cells without
bacteria. Plus, MNV can infect its target cells without bacterial help. So as long as the virus gets across the barrier infection can start.

Bacteria just make the process more efficient, somehow.


Robin writes:

Norovirus & mice

Viruses: the kind that keep you well!

With the shift in perspectives to microbiomes comes a paradigm shift. Koch’s postulates will remain valid within their box, but now we have to deal with the whole world outside the box.

“Ecosystems are not only more complex than we think, but more complex than we can think.” This quote from ecologist Frank Egler was probably based on a 1927 statement by evolutionary biologist J.B.S. Haldane, who said “[m]y suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose.”

Let us now try to revamp our understanding, so that a person who is full of it may be a well-adjusted individual in possession of a valuable resource.

And with reference to one of the TWIx podcasts (I don’t remember which), a mouse with symptoms would be a most unusual mouse: it would be a talking mouse!

Hayley writes:
Dear Twiv Professors,

Your discussion about the human virome and finding potentially beneficial viruses got me thinking. For bacteria, scientists can take advantage of so-called “universal” primers to amplify DNA from all sorts of species that may be present in a sample, giving them a sort of ecological snapshot of what may be there, even if they can’t culture it. Is there any method that we have now to take a general survey of what viruses might be present in a sample, even though they may not be causing any noticeable effects? I guess viruses are too varied to have universal primers — but couldn’t you start by priming for virus families that have consensus sequences in some area of their genomes, like where they code for their polymerase? At least then you could take a human herpes snapshot, or a norovirus snapshot, and thus piece together a partial view of the virome that way.

Thanks so much for your podcasts!

Peter writes:

Dear Doctores TWiVae,

I have a question in response to your discussion of Peter’s email, read in TWiV 305.

I don’t doubt that Norovirus can be transmitted via vomit. I am just wondering whether replication in the stomach is required. I would find it remarkable, if Norovirus is able to replicate at stomach pH. I assume that only the stomach content (and not the one of the small intestine) is ejected even during violent vomiting of a typical Norovirus infection.

I love all TWiX podcasts and listen to them mostly within one or two days of their release. Being 13 hours ahead in time of the US East coast, TWiV makes me looking forward to Mondays.

I am a biopharmaceutical process engineer and at my job viruses are something to inactivate / remove from the product, typically by low pH treatment and 20-nm filtration. Chromatography steps help too, even it’s not their primary purpose.

This is just my second email to TWiV. The first one was years ago for the discussion of the Vesivirus contamination of Genzyme’s manufacturing plant in Allston, Ma.

It’s 9.00 am in Incheon and currently 15°C and clear blue sky with a perfect Korean fall day (high: 21°C) ahead of us.

Regards from Incheon,


Kim Green writes:

Interesting question! There are some who believe that noroviruses might indeed replicate in the stomach.

I consulted with the gastroenterologist in my group. She said that normally, vomiting generally expels the stomach contents. However, with the heaving of vomiting, the duodenum can contract and upper intestinal contents can be regurgitated. When vomit is yellow, it is often the bile from the upper intestinal tract.

Robin writes:

Killing gut bacteria killed the patient.

I had a patient who was on coumadin (Vitamin K antagonist). Vitamin K is needed by the liver in the synthesis of a number of proteins including several factors in the blood coagulation cascade. Antagonising Vitamin K slows blood clotting and helps in conditions where excessive blood clotting is a problem.

The two sources of Vitamin K are green (leafy) vegetables and gut bacteria. Antibiotics, by disrupting gut bacteria, decrease available Vitamin K and enhance the effect of coumadin. Particularly egregious in this regard are the quinolones such as Cipro.

Well, this patient had been started on Cipro a few days before he showed up in the Emergency Department by ambulance one night with a new hemiplegia and a hemispheric bleed on CT. The INR (a measure of clotting, normal 1, therapeutic range usual 1.5 – 2.5, intensive 2.5 – 3.5) was 9. He deteriorated in the Emergency Department and died in hospital before the next sunset.

Just because it stinks, it doesn’t mean it’s all bad.

Martin writes:

I am a 69 year old in fairly frail health. The VA clinic gave me the high dose vaccination last month. If I start feeling flu onset, I plan to go to the ER and get an antiviral course.

I seem to recall you talking down the effectiveness of tamiflu against flu.

Should I be worried?

Joshua writes:

Hello Twiv-crew,

As fun as the recent Ebolavirus binge has been, I hope you find the time to talk about sea star wasting disease. A new paper in PNAS has associated the disease (which is rather vicious in its complete destruction of the organism) with high loads of Densovirus. As a lay person, I can’t find much information on this virus and hope you can inform. You are fantastic teachers and your listeners, dedicated learners.


Josh from San Antonio, Texas

Heather writes: 

Doctors TWiV,
Please please please consider the attached paper about sea star wasting disease for a future episode. I thought Bulldogs Go Viral was great! TWiV 310 was also great; it -almost- made me want to get out my old microbial genetics materials for review. It was nice to hear about the more everyday human dimensions of those involved in the pioneering work I studied during microbial genetics. On another note: I hate to admit it but I have minutely missed This Week in Ebola. Thanks!

Robert writes:


I have followed Professor Racaniello’s Coursera courses (Virology 1 & 2), and am a subscriber to This Week in Virology.

I recently stumbled upon an article regarding chlorovirus atcv-1, but couldn’t find any good scientific reference for it. I was intrigued by two things I read; that 40% of the small human sample tested positive for it, and, secondly, that it adversely affected cognitive ability, memory, and spatial awareness. In other words, a virus that makes people stupid and that nearly half of the population (seemingly) are infected with seemed eye-opening. But all joking aside, as a virology enthusiast, it seemed interesting and worth learning about. So I had some questions I was hoping you could answer.

What type of virus is chlorovirus atcv-1? How is the virus transmitted? What areas of the world/regions of North America is the virus native to? How long does an infection last before immunity is gained, if at all? Should the general public be concerned about it? How does one go about getting tested for it?

If you can answer my curiosities, I would be greatly appreciative.

Thank you sincerely,

– Robert J

Alberto writes:

Dear TWIVologues,

I’d like to suggest a paper for discussion that came out in PNAS:
Chlorovirus ATCV-1 is part of the human oropharyngeal virome and is associated with changes in cognitive functions in humans and mice

What do you think of it?

Best regards from Berlin, Germany!

Peter writes:

Dear Doctores TWiVae,

A headline too “good” not to forward the link to you:

Regards from Incheon (Korea),


John writes:

Dear TWiVers,

I thought I’d write in about something that really piqued my interest but has nothing to do with Ebola OR the weather (which is a balmy 12C here in New York today). Not that I mind hearing about Ebola. Or the weather.

A recent paper in PNAS has noted an association between a virus of green algae (Chlorovirus ACTV-1) and cognitive deficit in humans. They were able to show something of a causative relationship for gene expression and antibody effects from exposure to this virus in mice, as well as statistically significant evidence of cognitive deficits in mice exposed to virus-infected algae but not in mice exposed to naive algae.

Obviously there is a lot of work to be done before the science news headlines that say “virus makes people less intelligent” are validated, but what is really intriguing me more is that IF (big “if”, I know) the effects observed are directly due to infection of the mammalian algal host with the virus, then this constitutes an example of a virus infecting across kingdoms of life going from plants into mammals. If any other examples of such an event exist, I don’t know of them and would imagine that they’re rather rare. It’s still not the example of cross-domain infection that was asked about in a previous TWiV, but I thought you’d find it pretty interesting.

Here’s the paper:



Harold writes:

Long time listener, Temperature in my office cubicle 79.2 Degrees F. Don’t have a view out a window, but all fluorescent overhead lights are functioning. Saw this headline on multiple blogs. Tracked down the article at

Your thoughts? Can we conclude that the presence of this virus impairs the sampled subjects? Could there have been other factors at work? Would ingesting infected algae cause the DNA to be found in the throat swab?

Russ writes:

Vince and friends

I think you missed the point of Alice’s very short post. It is a haiku:

Love them
But they are SO long
I just don’t have time to listen.

Three lines, 15 syllables (17 in classic Japanese Haiku).


Also, read over my letter about airborne vs. droplet transmission. You still get them confused.

airborne = spread by small airborne droplet nuclei (residual of evaporated droplets), <= 5 uM in diameter. They remain suspended in the air for a long time, like dust, and can travel a long way with air flow, like out the door and down the hall. A filtered negative pressure room is ideal and a mask is needed when you enter the room. Examples: TB, measles, and varicella.

droplet = spread by large droplets like when you sneeze. They only travel 3 feet or so because they are heavy and fall out of the air rapidly. Wear a mask when you are close. Examples: adenovirus, influenza, and pertussis.

Love the podcast.


Marianne writes:

Hi TWiV hosts;

I couldn’t help but chuckle to myself when I heard you read Dave’s email regarding the confusion of receiving so many emails from Daves. Reminded me of a great comedy sketch from the classic Canadian comedy troupe, The Kids In the Hall. Its below and called ‘Daves I know’.

Keep up the great work!

Pat writes:

Dear Doctors,

Thank you for your excellent podcasts! TWiP # 76, Herpesvirus worms its way out, was fascinating, and led me to wonder whether pre-existing parasite infections may be one of the many reasons why Ebola has a higher death rate for residents of tropical areas of Africa, where parasite infections are more common, than for residents of the United States or Europe, so far, in these very few cases. In addition to the links you provided, this paper in Science looks at the effect of parasite infection on viruses:

Virus-helminth coinfection reveals a microbiota-independent mechanism of immunomodulation
Interestingly, a sort of editorial paragraph has been added, titled “Parasites make it hard to fight viruses.”

Do you happen to know if this interaction is being specifically studied with regard to Ebola, and whether addressing chronic helminth issues might help people be more resistant to ebola and less likely to die from it? Thanks!

Sam writes:

Dear TWIVome, I saw this on – a paper in PNAS describing vaccine resistance in a polio outbreak from 2010 in the Democratic Republic of Congo.

Bad news for polio eradication but from listening to TWIV on the regular it seems that polio eradication is already pretty complicated.

A few questions: It seems this strain was isolated during an outbreak – is it possible this mutation was wiped out with the outbreak? Could this mutation be overcome with more doses of the existing vaccines, or would a new version of the polio vaccine be needed? What, if any, are the prospects for a new polio vaccine?

Thank you for your perspective. Weather here in Tucson is clear and sunny as usual, with a high of 71, a low of 51 and humidity of 33%. Bit of a cold snap, but we’ll be back in the 80’s later this week :D.

Bill writes:

Thanks for the entertaining and informative program. Last week I thought I understood someone to say you feel obliged to respond to all emails. Well feel free to ignore this one if the question has already been answered.

I read the CDC recommendations for care of Ebola virus disease patients in hospitals including Bellevue, NIH etc. They seem clear for anyone in the facility “potentially exposed” down to developing sick leave policies. My question regards workers who don’t feel they have been potentially exposed. They don’t live at NIH so I assume some come to and from work on public transportation, eat out, go to PTA meetings etc. I can see no reason not to as long as they are asymptomatic. Given the near panic raised by one well nurse in rural Maine, perhaps it is better not to discuss all the Bellevue workers moving anonymously among us anywhere near Governors or media. How is this actually handled?

I am a retired Clinical Psychologist with no background in virology or communicable disease but taught interns in Family Medicine how to interview without falling out of their chairs for a while. I had the privilege to attend 8 years of noon conferences on many issues. There was an Epidemiologist on the faculty who repeatedly urged residents to ask patients if they had traveled recently, what kind of work they did (for potential exposures) and to consider educating themselves about the environmental factors affecting their patient populations. He was generally ignored by most residents but must feel thoroughly vindicated today. By the way, I am not aware of any of our residents practicing emergency medicine in the Dallas area!

Sorry to be so long but I have always admired writers who could communicate scientific ideas to the general population (Asimov, Gould etc). I was wondering if you had any comment on the book that caught my attention a year or two ago and that I recently reread, “Spillover” by David Quammen. If nothing else his narrative accentuated the role of veterinary scientists in field and lab research of emerging diseases.

Thanks again, Bill

Sandra writes:

Is it known if some body fluids have more Ebola virus than others? Particularly wondering if nasal &/or lung secretions have lower levels of virus than blood, vomit, diarrhea. Saliva?

Sandra in Dallas

Trevor writes:

Hello to my favourite virology podcast!

I’m a Canadian university student who’s interested in virology specifically the use of viruses as vectors in RNA interference which silences or ‘knocks down’ genes. I’ve been in correspondence with several professors at my university but unfortunately most of them don’t have the answers to the questions I have on the subject and since this is a somewhat new technology I’m having trouble finding places to research it. Do you know of any individuals who have done extensive work in this area or are at the cutting edge of this field? I have so many questions about why the effects of RNA interference are transient and how they might be used in the future. So if you know of any good texts or papers on it I would be very grateful. As always your work on the podcast is excellent and I think you and your cohorts have gone a long way to educating your listeners not just about virology but how to think critically and creatively about the field of science in general.

By the way, the weather here is about 12 degrees celsius and sunny.

Christophe writes:

Hi Vincent et al.


Just kidding this is not about Ebola virus.

I was having a discussion at home with the family about the flu shot just now.
The whole family got it the other day when we went grocery shopping as the pharmacy was doing free shots. (Huzzah for the Canadian health system)

I was joking about it being so easy I could go and get a flu shot every weekend when we do the shopping.

So, not that i would actually do this but I am curious.

If you don’t have a negative reaction from your first shot of a specific years flu vaccine, would each successive shot of the same vaccine increase the risk of a negative reaction (using up one more of your one in X chance of an adverse reaction) ?

or if you don’t have an adverse reaction to it – will you “never” have one

or is it that each injection is still a one in X chance of adverse effect each time you take it.

Are there other possible ill effects from having multiple doses of a flu vaccine?

Are there any potential benefits from having multiple shots?

thanks for the great podcasts and keep up the good work

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