Stephanie Karst writes:

Hi TWiV Team,

I’m so honored that you discussed my group’s norovirus paper last week. I wanted to touch on a few points that came up and provide a bit more context.

Regarding whether other RNA viruses are known to infect B cells, in addition to influenza virus as Kathy mentioned rotavirus can also infect B cells (e.g.,

Regarding why we would choose to use unfiltered stool as a source of virus knowing that there would be bacteria present that could contaminate our cultures, we already had evidence that commensal bacteria stimulated norovirus infections. We actually performed the antibiotic depletion studies in mice (Fig. 4D) well before we began our human norovirus experiments. Based on the bacterial enhancement of murine norovirus infection in vivo, we decided to compare filtered and unfiltered stool as a source of human norovirus in our cultivation studies. So this is one of those situations where the story flowed better when told out of the order in which the experiments were actually performed.

As speculated during your discussion, we always use antibiotics in our media. When we performed the E. cloacae studies to rescue infectivity of the filtered stool, the bacteria were actually heat-killed prior to incubating with the virus. Interestingly, heat-killed bacteria do not appear to stimulate infection of the filtered virus in the co-culture system suggesting that live bacteria are needed for the transcytosis process but not for stimulating infection of B cells.

Another question that was raised was how infection of immune cells residing underneath the intestinal epithelium could result in gastroenteritis. We don’t yet have an answer but can throw out some ideas we think about:

(1) Infection of immune cells could trigger the release of pathologic levels of proinflammatory cytokines that increase the permeability of the epithelial barrier. We think this possibility is rather unlikely though because norovirus infections are associated with only modest inflammation.

(2) As discussed in the podcast, the virus could encode an enterotoxin similar to rotavirus; if this were secreted from the infected immune cells it could act on the enterocytes basally. One correction – no one has yet proven that noroviruses encode an enterotoxin. [vr: I didn’t think so!] But many features of norovirus infections are consistent with this pathologic mechanism.
(3) Really hand-waving now, is it possible that noroviruses bind “nonpathogenic” commensal bacteria in the gut lumen and drive their transcytosis across the epithelial barrier? Some bacteria are nonpathogenic simply because they are unable to breach the epithelial barrier but they could potentially be pathologic if assisted in this process.

Best, Stephanie

Stephanie Karst
Associate Professor
University of Florida College of Medicine
Department of Molecular Genetics & Microbiology
Gainesville, FL

Randy writes:

Hello TWIV hosts,

The current conditions in Phoenix…. miserably hot. 100F, 8% humidity, 4 mph winds. Next week… highs of 108.

In TWIV 280 you read my email (/twiv/twiv-280-letters/) regarding canine distemper virus. In episode 289 you read an email from Alice, who had been through a similar ordeal. She asked if the distemper vaccine might have made her dogs illness worse. There is a case where it’s thought it could do so.

Consider the following…
“Concomitant with immunologic recovery during the further course of the disease, inflammation occurs in the demyelinating lesions with progression of the lesions in some animals. A series of experiments in vitro suggested that chronic demyelination is due to a bystander mechanism associated with the virus-induced immune response in which antibody dependent cell-mediated reactions play an important role.”

“The mechanism of inflammatory demyelination in canine distemper encephalitis (CDE) is uncertain but macrophages are thought to play an important effector role in this lesion. Serum and cerebrospinal fluid (CSF), containing anti-canine distemper virus and anti-myelin antibodies from dogs with CDE were tested for their ability to generate reactive oxygen species (ROS) in macrophages in primary dog brain cell cultures using a chemiluminescence (CL) assay. The majority of serum samples and several CSF samples from animals with inflammatory demyelination elicited a CL signal in infected dog brain cell cultures. In contrast, none of these samples induced a positive response in uninfected cultures which contained large numbers of myelin antigen-presenting cells, although defined anti-myelin antibodies lead to a marked secretion of ROS in this system. It was concluded that antiviral antibody-induced secretion of ROS, known to be highly toxic for brain tissue, may play an important role in white matter damage in inflammatory lesions supporting a previous hypothesis of bystander demyelination in CDE.”

This isn’t well understood but it’s conceivable to me, and a few virologists I’ve spoken with in the past that the increase in anti-cdv antibodies produced in response to the vaccine adds “fuel” if you will, to this bystander demyelination and could lead to worsening neurologic symptoms similar to what Alice described. Additionally, anecdotal as it may be, there appears to be a belief in a surprising number of veterinarians that giving a CDV vaccine to an animal that has been naturally infected can cause “complications”. There was little or no elaboration on “complications”.

All that said, my non-virologist brain tends to think this does not apply to Alice’s dog since, based on her description, he was probably acutely infected. This is a biphasic demyelinating disease. I suspect his worsening condition was the result of primary demyelination and inflammation caused by viral replication in the CNS rather than the secondary aforementioned cause.

Thoughts? Do I get an amateur virologist merit badge?

Thanks again for the great show. I anxiously await every new episode and have even begun listening from episode 1.


Patty Pesavento replies:

The short answer is that with regard to both “old dog encephalitis” (ODE) and post vaccine distemper, only individual animals have been examined, and no one knows what is going on, or has gone on, with the actual viruses themselves in these cases. There is an unpredictable, and sometimes prolonged period of persistence that can precede systemic infection, and this (understandably) creates healthy skepticism about whether or not “post vaccine distemper” or ODE is actually a slow response or a recent exposure. We are blissfully unencumbered by any solid data, so the conversation is potentially endless.

Quick paper summary: Fairley’s paper from New Zealand describes 2 cases, vaccinated litter-mates that were persuasively “ post-vaccination” because 1) while NZ still has a CDV vaccination program, CDV is simply not seen by NZ veterinarians 2) The tissue distribution, b/c in both dogs non-nervous tissues were spared, which is atypical for the natural course of “acute” infection and 3) While these dogs were litter mates, they were adults when they developed encephalitis, grew up geographically isolated, and developed disease in single dog households. The presumption in these cases, and for other ODE and post-vaccine CDV, is that there is an alteration or deficiency in host response (immune suppression, aging, or a second pathogen) that permits viral attack (by pre-existing, “persistent” virus) on the nervous system. What we’ve missed in the paper was sequence data proving that the virus was a vaccination “ strain”. Also, there is no way post facto to analyze any deficiency, if one existed, in the immune response. I have heard many state that this is an autoimmune response, but I can’t buy that, first of all because it is a “back-in” theory and secondly because there is plenty of virus in the lesion (glia, primarily). So the exciting question really is where in the heaven the RNA virus, vaccine strain or not, can persist, and what triggers the cytolytic infection in these cases. There are some similarities between CDV/CNS localized disease in dogs and measles/subacute sclerosing panencephalitis in humans.

Other CDV thoughts: There have been primate outbreaks of CDV (Sakai, JVI, 2013), and so an important question that comes right to the fore is what you touched on in TWIV#286: Would having a large group of non-vaccinated people provide a niche for CDV? If so, I’m moving to New Zealand. My laboratory has explored the issue of cross species transmission by analyzing full-length sequences of CDV isolates obtained from a cohort of susceptible mesopredators (dog, grey fox, striped skunk, raccoon) from northern California in one season (temporal snapshot) and from a single county (geographic snapshot). For raccoons, we also sequenced isolates at the same time period but from multiple locations. We’re still considering what we have found, probably need Duprex’s help, but there is a clear species rather than geographic grouping of viruses.

I consider the raccoon a virus star here. Whether RacPyV or CDV… a star. And since Europe is now declaring war on raccoons (, we can no longer say it is the quintessentially North American mammal, but they are, everywhere they’re found, at the absolute closest interface between wild animals and humans. It would help me tremendously with research funding if raccoons were included in the Affordable Care Act.

As an aside, and as one of the few veterinarian pathologist-pseudovirologists in your herd of listeners… I would add that the study of the natural history of viral infections, including the study of viral pathogenesis in true cellular and animal targets of disease, is interesting, and perhaps undervalued (I’m Italian, and FYI my hands are flying around in print here). As Duprex stated we cannot make decisions about how to protect a population without reading its true tissue travel diary (sic).

Take care, your energy is remarkable.

It’s rainy and cold in Ames, Iowa. Back to sunny albeit dry CA tomorrow.

Patty P.

Robin writes:

C & F conversion

[he sent:]

Pritesh writes:

Hello Dr. Racaniello,

Here is some viral news from University of Florida I would like to share. I am sure Dr.Condit will like this since it’s about POXVIRUS


PhD student
IDP Biomedical Sciences Program
University of Florida

Phillip writes:

Kathy et al.,
In this week’s broadcast, the group talked about the number of PhDs in biomedical research programs, and the possibility of encouraging them to teach high school (HS) students. The debate seems to be whether PhDs from an exclusively biomedical field would improve science education in high school. My wife (who you sing with) is a grade school music teacher, so I have additional knowledge from her about being a teacher in Michigan.

Here are my 2 thoughts:
1) There are multiple programs in MIchigan that offer a PhD in science education (see links and quote below). These programs combine research with advanced training on teaching science, and students in such a program generally already have teaching experience. While the typical individual with a research-intensive PhD may have excellent research and critical thinking skills, he or she isn’t, however, likely to have experience teaching adolescents and dealing with all of the non-science aspects of K-12 education.
From the College of Education at Michigan State University website:
“The Ph.D. emphasis in science education is a component of the internationally renowned Curriculum, Instruction, and Teacher Education (CITE) program at the College of Education at Michigan State University. The mission of science education is to blend science theory, research, and practical application to explore current issues in science teaching and learning. The science education faculty brings a range of theoretical and methodological perspectives to their work, including cognition, sociocultural, and feminist/critical perspectives using both qualitative and quantitative methods.”

2) I have come across several grad students and postdocs that think they can “just go get a job” as a HS teacher if all else fails. The fact is you can’t just walk in there and teach. You have to become certified, which in Michigan, means meeting a variety of coursework requirements, an internship experience, and passing particular tests. At UM, the College of Education website appears to offer options that can be completed within a year if separate from another degree. This certificate, once earned, must be periodically renewed, pending further professional development. Michigan does offer an “Alternate Route” program for individuals who qualify to complete certification coursework while holding a teaching position. In either case, it has been my observation that various school administrators seem to have different priorities in hiring. Some prefer to hire a candidate with the most relevant classroom experience, with or without a graduate degree. In other districts, the cheapest qualified candidate is selected due to budgetary constraints. In either situation, a person with research intensive PhD without prior K-12 teaching experience may be viewed as a less than ideal candidate for that district.

If the quality of HS science teachers is in question, another way to address it might be offering current educators different professional development (PD) opportunities that address some the issues discussed by the group. Most science education PD focuses on improving effective education techniques. Perhaps a university might offer a non-degree PD program for science teachers to participate in a research lab during the summer in some form.

Phill Delekta

Phillip C. Delekta, Ph.D.
Research Fellow
Department of Internal Medicine-Division of Infectious Diseases
University of Michigan Medical School

David writes:

Dear Vincent and friends,

Your session with Janet Butel and Rick Lloyd was fascinating. Especially enlightening were Janet’s thoughtful comments about the proposed association of SV40 and human cancers.

I have a connection to Janet, as Fred Rapp, her thesis adviser, was the founding chair of our department at Penn State’s College of Medicine and he was here for my first decade or so as a member. Fred built a unit, currently called the Department of Microbiology and Immunology, that still consists primarily of virologists. Among the current faculty are ten virologists and two others who do viral pathogenesis. Fred helped establish an outstanding training program here and our trainees have gone on to successful careers in academia and elsewhere. Although we no longer have a separate departmental graduate program, training in virology is still provided though an option in our umbrella Biomedical Sciences (BMS) graduate program.

Janet is rightly proud of the virology program at Baylor, which incidentally not only gave us Fred Rapp, but also Dick Courtney, who chaired our department from 1990-2012. That being said about Baylor virology, we think we measure up very well here at Penn State Hershey. We encourage your listeners who are interested in post-graduate or post-doctoral training in almost any aspect of virology to consider us. We eagerly anticipate the “twiv bump.”

With respect to another virology program you discussed, Maurice Green founded the Institute for Virology at St. Louis University in 1964 and many fine virologists established their careers there. I had the opportunity to interact with Maurice, who was the postdoctoral mentor of Heschel Raskas, my postdoctoral mentor at Washington Univ (St. Louis). Among Maurice’s contributions, and they were many, was an exhaustive analysis of tumors for adenovirus DNA, following the discovery that adenoviruses produce tumors in rodents. The upshot was that there was no evidence linking adenoviruses to cancer in humans.

It’s 27°C and overcast in Hershey. Visibility is 10 mi and the ceiling is 33,500 ft.

Many thanks for twiv. Although you wouldn’t think it was possible, it keeps getting better.


David J. Spector, Ph. D
Professor of Microbiology and Immunology
Department of Microbiology H107
College of Medicine
Penn State Hershey

Jing writes:

Hi Vincent,

Recently after bragging about studying poliovirus replication for my Ph.D research, I was questioned by an anti-vaccine guy about how the polio vaccine keeps up with the high mutation rate of the viruses. I played cool and mumbled something about the vaccine recognizes the most conserved features etc, however immediately I started to wonder about the same thing in the back of my head.

As an RNA virus, polio is known to have a high mutation rate near the edge of error catastrophe, then why so far we only identified three serotypes of polio and all of which are targeted perfectly well by the vaccines unchanged since Salk developed them in 1950s? What a failure for poor polio if from all its potential “adaptive” quasi species pool, not a single virus can bypass the vaccine induced immune response? Is there genetic conflict ever been observed between polio capsid and the polio receptor?

Love your podcast and keep up with the great work!

Shane writes:

Hi TWIV gang,

I have written a few times to your show as a layperson with an interest in science. Well now, after some encouragement from a scientist friend and my enjoyment for science kindled by TWIV, I am finally making a start on a science degree at UQ (University of Queensland). I start my first class in less than a month entitled “Genes, Cells & Evolution”, and am planning on Majoring in “Biomedical Science” and “Microbiology”, I am especially looking forward to Virology, Parasitology and Immunology.

Without the constant companionship / mentorship of the TWIV, TWIM and TWIP crew I would have never thought of venturing outside my current field of experience. I would also especially like to thank Vincent for his Virology courses on Coursera that I have been a rabid consumer of.

Keep up the great work, hoping the TWIX media empire will continue to be a big part of my science education.


Shane from Australia.
It’s a clear day 19°C , clear sky with WNW winds of 13KPH, dew point is -2°, Pressure: 1011 mb

Steve writes:


Hi Vincent,

I know you and the team at TwiV hate all the hype from the anti-vaccination lobby, as much as I do, but, you may have noticed that, recently, they have been engaging in something of a feeding frenzy over an ex CDC scientist, who has supposedly admitted to altering data so as to hide an association between the vaccine and MMR.

I have not been following this ‘debate’, as I got tired of it years ago, but, I expect that, whatever these particular ‘revelations’ are, they do not really make any significant difference in the whole body of data. I would, however, be interested in your team’s take on all this, particularly as you are scientists who, are more likely to be heeded than most!

Apologies for bringing this one up again, but I think it does need nipping in the bud.

Many thanks,


Neil writes:

Hi Vincent

I couldn’t resist sending this in so that you and Alan could see it if you haven’t already. Not news, but more awareness is never bad.


David writes:

Dear esteemed scientists of TWIV,

Writing from Marina del Rey California. Its 65 F (Not surprisingly, our range is 60-75 all year). The Humidity is 55%. wind WNW at 1 mph. More importantly, the surf forecast shows a small mix of NW swell and SSW swell. Surf is mainly in the 1-2’+ zone, and local standouts surf spots are seeing waist high sets with the right tide.

You keep telling listeners that ebola has a 21 day incubation period. Data from the current EVD epidemic in West Africa is probably your source for this statement. For instance, many people cite the New England Journal of Medicine’s publication from the WHO Ebola Response Team BUT, as stated in that article “Approximately 95% of the case patients had symptom onset within 21 days after exposure”. Indeed, Figure 3A in that article shows many cases (or rather, 5%) occurring outside the 21 day period. You see where I’m going with this question?

Does our public assurances that 21 days is THE incubation period worry you at all? I say “our” assurances because I advise our public health department and am participating in our city’s ebola preparedness. (When I was asked to join the ebola team the first thing I did was learn about viruses and ebola from TWIV. A god send! ) Please, look at Figure 3A in the NEJM article and tell me why you are never expressing your uncertainty about this 21 day policy. As you rightly point out, scientists are loathe to express certainty. And 5% of cases beyond the 21 day period is not a trivial amount ofy cases.

Our public health department, like many in the US, is currently monitoring several people in home quarantine for EVD. They will follow them for 21 days just as recommended by the CDC. If a single one of those quarantined persons subsequently develops EVD after quarantine is over, that is after 21 days since exposure, this whole 21 day thing will be blown apart. Our credibility (yours, mine and ours) will be damaged.

If you were advising the mayor of Gotham would you tell him 21 days or would you tell him longer—and how much longer? Recognizing that, in this case, trust in public health and its scientists ,maybe as important as best use of resources and trump the extra week of lost freedom that quarantined individuals might face if the period were longer. (Don’t cop out and say that you are not advising, you are just virologists….)

I greatly enjoy your show. I was invited on to a UCLA panel on ebola held for the community last week, and I told the assembled audience to listen to TWIV if they wanted to learn about ebola. If I were still a medical student I would be completely drawn into virology (and infectious diseases at Mt Sinai) by your show (I trained at Albert Einstein College of Medicine and NYU). Great work!

David Eisenman, MD MSHS
Associate Professor of Medicine
David Geffen School of Medicine at UCLA
Associate Professor of Public Health
UCLA Fielding School of Public Health

Simon writes:

Dear TWiV team,

What a fantastic episode with Tom Solomon!!!! While the ebola episodes have been very interesting, it was great to take a break with something little different!

I have recently been listening to Relatively Prime, a set of kickstarter-funded podcasts about mathematics ( In episode 4 the discussion is about how working on one problem can sometimes lead to very unexpected results or applications in another field and there was a fascinating discussion about a novel approach to predicting influenza (and other) outbreaks.

In brief, there is a phenomenon called the Friendship Paradox which roughly says that most people have fewer friends than their friends have, on average, which was first introduced in the excellently named paper “Why your friends have more friends than you do”. Intuitively this is because people with a lot of friends are more likely to be your friend, and has been consistently observed in physical and online social networks.

Nicholas Christakis from Yale University has since then used this phenomenon as an approach for forecasting contagious outbreaks within populations. The idea is that rather attempting to explicitly map a social network to identify the most highly connected individuals who will act as hubs for the spread of a disease, one can more simply use the friends of randomly selected individuals. By the Friendship Paradox, these individuals will be more highly connected. In a study from Harvard in 2009, they were able to predict a flu outbreak in the overall population by about 2 weeks.

I don’t know if any further work has been done on this or if it has ever gained popularity within the epidemiologist’s tool-kit (do you?), but I thought it was a really nice example of the way research in one area can sometimes lead to interesting applications in another.

Please see links below for reference.

Thanks and keep up the great work on Ebola and all things virology in general.


Segment from Podcast:

Why Your Friends Have More Friends Than You Do

TED Talk:

PLOS One Paper:

Nicholas Christakis
Mark writes:

Hello There TWiV-osphere,

Its raining here in San Jose California, while you on the East Coast are being belted with cold weather, and worse. Does yesterday’s punishing 5+ feet snow fall in Buffalo NY make co-host Condit glad he now lives in Florida?

The year 2014 is coming to an end. For this listener it has been a super year for TWiV, and related shows TWiM and TWiP. It was great to have to diversity of field trip visits to conferences and other researchers labs. TWiV is a nice community. This year we revisited old friends like Flu, Polio, and Rabies, while making new friends visiting with Ebola for several months.

As the Holidays approach many think about gifts to give. Finding a unique gift is a challenge. Here is something new. My nomination for listener pick of the week is the site — they make “doll” like replicas of viral and bacterial pathogens. These are great gifts to challenge a child’s imagination and, hopefully, catalyze an interest in microbiology, OR to give to a scientist or physician. Products are inexpensive, in the $10 to $15 dollar range. Attached are screen grabs of their replicas of Giardia, or viruses Rabies, Polio, Malaria, and 2014’s surprise hit the Ebola Virus.

All the best.


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