Rich writes:

Re John’s (ee cummings) letter:

John writes of fear of science and implies mistrust of science and scientists on the part of some laypeople.  He points out that critical thinking does not necessarily require a science education.  He writes of our ivory tower.  Conflating these and other comments I am reminded that at various times on TWiV we have made offhand comments to the effect that so-and-so is not qualified to evaluate or understand this or that because she/he is not a scientist.  This sort of statement sets scientists apart and isolated from non-scientists, which is exactly the opposite of what we are trying to accomplish with TWiV.  We want to be inclusive and have everyone join in the fun and insight that science brings.  John is dead right that one does not have to have a specific training to be a critical thinker, or even to understand in significant detail complex scientific concepts.  We see this all the time in the correspondence we receive.  So thanks, John, for the reminder that we are all just humans and that our mission should be to help each other through this life with whatever gifts we have been given.

Robin writes:

Aerosol vs. droplet:

When a fixed wing aircraft on its rollout reaches rotation speed, it transitions from wheelborne to wingborne. Once it is fully wingborne, it is airborne.

The interaction with air is at the surface of the object. The surface decreases by the square root while the volume and mass decrease by the cube root as objects get smaller. Beyond a certain point, even without wings, the surface area is adequate for the gentlest of air currents acting on it to produce enough force to keep the object airborne long beyond the ballistic trajectories produced by forces acting on projectiles.

The “sol” suffix in aero”sol” refers to particles in suspension – borne by – the medium. The gentlest of currents in the medium delay the settling out of the particles.

The particles in a spray are initially all “ball”istic – like a “ball” that is thrown. If they are small enough, or can become small enough soon enough through evaporation of contained liquid, then they can transition from ballistic to airborne, much as an aircraft catapulted off an aircraft carrier transitions from ballistic to wingborne/airborne.

In the case of the particle, the air currents exert enough force on its surface area to support its mass. In the case of the aircraft, the thrust of its engines increases its airspeed, and thus the force exerted by the air on its wings.

Sorry if this seems like preaching to imbeciles: some folks, like some bullfrogs, may still not get the difference between a (ballistic) droplet spray and an airborne aerosol.

Cameron writes:

Hi Guys,

Great show, I listen to you guys every week and love what you do.

I especially like that you counter all the misinformation in the media currently, that Ebola could just so easily mutate and become airborne.  I am tired of hearing of how since the Reston strain of Ebola can transfer from pigs to primates, that it demonstrates that Ebola can become airborne. Especially when it doesn’t then spread between the infected primates! Not to mention the fact that the Reston strain isn’t lethal to humans. It is also relevant that the Russians tried to weaponise lethal strains of Ebola into an airborne pathogen and FAILED!   I blame movies like “Outbreak” for the fear in the general population that viruses just decide to change their mode of transmission, even when it has not been observed in the real world before!

Anyway the questions that I do have about this particular epidemic;

It is my understanding that Ebola as a zoonotic virus may infect other mammals such as dogs, without them necessarily becoming symptomatic of the infection.   Since the current situation in countries like Liberia where carcasses of the deceased are being left lying around and assuming that they may be being eaten by dogs, birds and other carrion feeding animals.  What would be your view as to the possibility of the developing new reservoirs of the virus?  In a similar fashion to the crows becoming a reservoir to the West Nile virus in the US.  Is it your opinion that in the long term this outbreak could be more difficult to control than the current estimates would assume?  Or do you think that the possibility of new reservoirs of infection is insignificant?  It would seem to me that this current outbreak is a little different from past outbreaks, since the number of cases have overwhelmed the medical response and have affected the ability of authorities to even collect the dead from some regions.

BTW, I agree that mosquitoes are of virtually zero risk in spreading Ebola.

Cheers from Down Under (Australia)


Dawn writes: 

Greetings –

I am very happy to have learned of your podcast.

However, I was really concerned while listening to your recent podcast on Ebola.

Specifically, I was incredulous that your three hosts did not even know the incubation period of Ebola.  (I’m glad you looked it up!)  I was dismayed how you seemed to disregard/downgrade transmission via semen.  Incubation to infection to transmission can vary from a few days to several weeks.  One of your hosts seemed to suggest that any man exposed to the virus would immediately not be inclined towards having sex – at any time – before he gets sick, or during the long convalescence – even though he’s potentially infectious for up to 2 months. Come on!!!

I was dismayed by this discussion.  Sex and prostitution are rampant all over the world …. and prevalent in Africa.  As a public health nurse, I almost could not believe what I was hearing.  You almost seemed to disregard sexual transmission of Ebola — which is near criminal, in my opinion.

I was also kinda non-plussed by your flippant, chatty treatment of this disease that is killing hundreds.  Although I can understand it.  Health professionals have a whole new level of black humor.

I realize you’re doing important research. I do love your podcast.  I know you’re not interested to epidemiology — or the broader social issues.

So, I won’t talk about the weather here in NC, nor will I ask you to be more PC or more careful where Ebola is concerned.

Except – DAMN – for the hosts to have to look up vital info on the CDC site – simple facts that YOU DON’T EVEN KNOW …. maybe stick with things you understand more (i.e. NOT Ebola.)

Or pick other topics.


Thilo writes:

Hi Vincent,

first of all thank you so much for your podcasts they keep me sane and educated in the traffic jams on my way to work.

I have a strange question but do you happen to know how it might be possible to get involved into the efforts in the ebola outbreak.  Currently I am unfortunately not in any institution that is even remotely involved in any aid work.

As I am UK-based, asking you from the other side of the lake maybe does not suggest itself,  but so far I had no response from the charities (Red Cross, MSF etc.).

Anyway a bit about myself:

Currently I am a PhD student (Biophysics for some reason) but have previously gotten a Bsc (Hons) in infectious diseases from the University of Edinburgh. Further I have been on a one year course in forensic science and medicine.

Before joining university I have been working as a ambulance technician for the German Red Cross. Currently during the summer months I am a beach lifeguard for the Royal National Lifesaving Institution (RNLI) in Scotland.

Already during my time at school I have been in Lambarene (Gabon) as a volunteer for the University of Tübingen (Germany) to collect blood samples for a research project about malaria.

It would be great if you could let me know if you had any idea how I could go about that or if you know anyone who might have any use for myself.

Thanks again for your podcasts and keep up the work am always looking forward to them.

Thanks a lot


Ps.: as you might suspect here in Scotland it is windy, wet and cold.

Scott writes:


The other day I listened to your interview on NPR in which you seemed quite confident that the risk of spread of the Ebola virus by aerosols is currently nonexistent and that status is extremely unlikely to change via mutation.

I would like to direct your attention to the following article, which suggests that indeed there is evidence, however weak and as yet unconfirmed, that Ebola may be weakly transmissible via aerosols:

Perhaps you should review this and correct yourself at least via TWIV, if not via NPR.



Cartago, Costa Rica.

Kevin writes:

Greetings Doctors TWiV!

On the most recent TWiV (#303 – Borna this way), while discussing the quirks of bats in relationship to viral infections (~00:25:30), Vincent brought up the duplications of genes involved in oxidative stress due to the higher metabolism, which got me thinking about a paper my graduate lab recently published about the relationship between mitochondria, peroxisomes, and anti-viral signaling (link).

The lab had previously shown that the cytosolic RNA sensors (RIG-I like receptors) can engage their signaling pathway from two locations: mitochondria or peroxisomes. The take home-from this new paper is that the signaling pathways engaged are different – signaling from mitochondria induces type-I interferons, while signaling from peroxisomes induces production of type-III interferons.

Not much is known about the difference between type-I and type-III interferons since until now, everyone had observed them as co-regulated (and the dominant type-III isn’t expressed in mice), but one interesting thing this paper showed is that as cells get more peroxisomes relative to mitochondria, they increase type-III interferon production, and if you eliminate mitochondria from cells entirely, you get a dramatic increase.

Back to the bats: their altered metabolism almost certainly affects their mitochondria/peroxisome ratio, and this could lead to dramatic differences in their antiviral responses. This could also explain why they’re more tolerant to a lot of viral infections that we’re not – does anyone know if this is more often the case with RNA than with DNA viruses?



PS – Audiommunity (tagline: “A podcast about our bodies’ never-ending fight with the outside world”) recently hit double-digits – we’re almost to Vincent’s magic number! (he once said that when you hit episode 12 with podcasts, it suggests that you’re here to stay, since people who aren’t serious will quit well before then).

Steve writes:

Hi Vincent & team,

I don’t know about your American varieties and fridge temperatures, but here in England, if one tries to grow tomatoes outdoors there is always a bit of a gamble how long to leave them outside, because the first cold night has them all on the ground, and if you bring them indoors, even though they may, initially look fine, they rapidly rot, instead of ripening.  If, on the other hand, you bring the whole vine indoors and hang it up, before the cold gets to the fruit, it will be fine for months.  I’ve sometimes kept tomatoes in a bowl from one season until the next.  The last, small, ones of the year, that ripen slowly in the cool, like this, always taste much better than the ones picked in the height of Summer.

A similar situation is in the transport of soft fruit, like peaches.  I used to deliver organic fruit and veg, and had to pick up from the wholesalers.  It became clear to me that the fragile fruit like peaches and nectarines were pulled off the trees none too carefully and then rapidly chilled before the bruises could develop.  Thus we would deliver fruit that looked great, but was, in fact, dead, and bruised: as soon as it warmed up, it rotted, and, unless you ate it straight away, you ended up throwing it away. This meant that, if the fruit had been picked not quite ripe, and customers unknowingly waited for it to ripen, they just had to watch their expensive organic produce go to waste.  I used to get quite outraged by this dreadful waste, when organic and sustainable were supposed to go together, yet this stuff had travelled around the world just to be thrown away, thanks to negligence or just, plain, don’t care.

I’ve not read the chef’s piece you refer to, but I would be surprised if he was able to keep any tomato once it had been in the fridge.  I’m quite sure that my own fridge would kill most of the tomatoes I’ve seen.  (Incidentally, while on the subject: don’t buy shiny tomatoes or peppers: they are not ripe and are still swelling.  When they are ripe, they become duller and maybe a little wrinkly.  For peppers especially, they tend to get sold off cheap when they are wrinkly and dull: they may even be thrown away: but this is when they actually taste the best!  I would never buy shiny fruit, and have picked up many a tasty bargain, as a result.)  And I never put fruit in the fridge unless I’m actually freezing it!

All the best,




Justin writes:

Brazil releases ‘good’ mosquitoes

21C clear and beautiful almost Fall day here in NY.


Analytical Chemist

Long Island Analytical Laboratories, Inc

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