How Does Stress Affect Susceptibility and the Expression of Disease?

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Del curso dictado por The Pennsylvania State University

Epidemics - the Dynamics of Infectious Diseases

568 calificaciones

The Pennsylvania State University

Epidemics - the Dynamics of Infectious Diseases

568 calificaciones

Not so long ago, it was almost guaranteed that you would die of an infectious disease. In fact, had you been born just 150 years ago, your chances of dying of an infectious disease before you've reached the tender age of 5 would have been extremely high. Since then, science has come a long way in understanding infectious diseases - what they are, how they spread, and how they can be prevented. But diseases like HIV/AIDS, Malaria, Tuberculosis, or the flu are still major killers worldwide, and novel emerging diseases are a constant threat to public health. In addition, the bugs are evolving. Antibiotics, our most potent weapon against bacterial infections, are losing their power because the bacteria are becoming resistant. In this course, we'll explore the major themes of infectious diseases dynamics. After we’ve covered the basics, we'll be looking at the dynamics of the flu, and why we're worried about flu pandemics. We'll be looking at the dynamics of childhood diseases such as measles and whooping cough, which were once considered almost eradicated, but are now making a comeback. We'll explore Malaria, and use it as a case study of the evolution of drug resistance. We'll even be looking at social networks - how diseases can spread from you to your friends to your friends' friends, and so on. And of course we’ll be talking about vaccination too. We’ll also be talking about how mobile phones, social media and crowdsourcing are revolutionizing disease surveillance, giving rise to a new field of digital epidemiology. And yes, we will be talking about Zombies - not human zombies, but zombie ants whose brains are hijacked by an infectious fungus. We're looking forward to having you join us for an exciting course!

De la lección

Ask Us Anything Videos

The videos accessible in this module are responses to questions that have been posed in previous sessions of this course. We invite you to look around here as an additional resource to answer questions you might have yourself or explore topics that pique your interest.

Dr. Moriah Szpara and How/Why do viruses like Varicella and Herpes Re-activate Themselves?7:53

What are the Challenges to the Eradication of Pathogens and Setting Eradication as a Goal?6:57

How Does Stress Affect Susceptibility and the Expression of Disease?6:17

Has there been a Collective Change in Human Behavior in Response to Sexually Transmitted Diseases?9:58

Conoce a los instructores

Dr. Ottar N. Bjornstad
Professor of Entomology and Biology
Department of Biology
Dr. Rachel A. Smith
Associate Professor
Department of Communication Arts & Sciences and Human Development & Family Studies
Dr. Mary L. Poss
Professor of Biology
Department of Biology
Dr. David P. Hughes
Assistant Professor of Entomology and Biology
Department of Biology
Dr. Peter Hudson
Willaman Professor of Biology
Department of Biology
Dr. Matthew Ferrari
Assistant Professor of Biology
Department of Biology
Dr. Andrew Read
Alumni Professor in the Biological Sciences, and Professor of Entomology
Center for Infectious Disease Dynamics
Dr. Marcel Salathé
Assistant Professor of Biology
Department of Biology

All right. So,

we can only hope that this course isn't a major source of stress for any of you.

Sometimes [LAUGH] it's a source of stress for

us but we hear a lot of messaging about stress and

health and the potential interactions between stress and infectious disease.

And a lot of people have been asking questions about this.

This is particularly come up in in a lot of the understanding about herpes

viruses where people have, to tend to see flare-ups of herpes viruses when they're

under acute stress because of things in their life and what-have-you.

Right? So I want to open up

the broader question of how does stress impact both susceptibility?

So you're likely to becoming infected, and the expression of disease symptoms.

So, how severe the infection with the pathogen can be.

So do you want to start with herpes viruses?

I want to start with herpes viruses.

That's a good one. Yes.

So, to start with herpes viruses, herpes simplex virus is

certainly a classic one where we know that symptomatically genes

are frequently induced after an extremely stressful experience.

So, to give examples,

that would be something like a long bout of drinking, [INAUDIBLE] work.

Preparing for an exam.

Even sitting in a hot tub,

which feels relaxing, is actually a physical bodily stress.

So it doesn't have to be something unpleasant, but

something that really changes your body chemistry, or

your body environment and your physiology.

For a herpes virus,

that is the type of thing that can wake it up out of this quiescent latent state.

And it's not that your body in particular releases a molecule that

would directly bind to the viral genome or a protein there.

But more that there's a signaling cascade of steps in between your body's

response to a stressor and the immune system,

which is normally providing surveillance on the one hand.

And also the neurons that this virus in particular goes latent in.

So for the viruses that I study, you think about both of those.

But I think for many of the other pathogens that we even comment on, we're

really mostly talking about suppression of the immune response or transient

depression of the immune response that allows a flare up to take place.

Or an infection to get through a barrier that should of otherwise stopped it.

Can I ask you another herpes related question?

So one thing which I've found really puzzling is, so with the simplex virus,

it seems very clear that the quiescence and reactivation is a,

it's a great strategy because, and they come out of, of dormancy.

I don't know every few months or every half a year I don't know,

I don't know quite how often it happens, but it's clear that it's,

it's very good for transmission, maintaining the general of transmission.

But now I've been always wondering about chicken pox.

Mm-hm.

Since so it's chicken pox is acute and transmits very well, but then.

The crescent face can last for decades.

It does.

And so, do you think is my question is so

to what extent do you think shingles an important epidemic, so

it's clearly medically very important because it's painful and horrible.

But epidemiologically you, how important do you, do you think Shingles is for,

for a virus?

So the, the folks who spend their whole labs and

their lives studying VZV think that the, the theory for

why this happens is that it's actually grandparent to grandchild transmission.

That's the cycle.

Isn't that neat?

When when this was first suggested I thought oh,

that's, what a neat and different strategy, right?

It's unfortunate that this is the case, medically speaking.

But from the virus's perspective, shingles and the reactivation that happens in

that upper level generation, provides a great opportunity to get past

the immunity that most adults of our age have and reach the non-immune children of,

you know, that of course in essence, the grandchildren.

So there's infectiousness going on with shingles?

Yes.

Oh yes. Skin.

Mm-hm.

So the, the painful difficult nature of

shingles is the part that lingers on afterwards.

It's often called neuropathic pain.

But that initial moment where you have this dermatome that comes out

with a visible lesion, people are extremely infectious.

And it can, it doesn't always happen in people of the grandparent's age.

I know plenty of people my own age who can have shingles and outbreaks.

But they'll literally advise you to stay away from your own young children, or

from other people's young children during that stage so you don't infect them.

And once it's in young children, they also transmit horizontally.

So in, in evolution terms, grandparents are a bit of a conundrum.

So, so most organisms die after reproducing, and you don't have this long

period of time after say, menopause in women where you have a very active life.

In terms of evolution biology,

we've come around to understanding with all data from [COUGH] excuse me,

long-term studies of Finnish populations over many hundreds of years

that grandmothers perform a very essential duty, it's called the Grandmother Effect.

They help their daughters raise their own, their granddaughters.

And because of kin selection this is beneficial.

And you can see that the benefit of grandmother when the mother is having male

offspring ,versus twin male offspring,

versus female offspring, because males are more expensive.

The grandmothers allow those offspring to grow up.

So my question is do we know if shingles is more present in females,

grandmothers versus grandfathers?

You know, I don't know the answer to that question.

I'll have to look it up afterwards.

I can certainly say that it's an unusual strategy.

I agree with you.

The grandparents strategy for that as a virus to reactivate there and move on, but

something that's useful to reflect on for herpes virus's.

They're very species specific, so

this human one didn't cross over into humans anytime recently.

It's been millennia, so as long as it took to evolve the Grandmother Effect.

Yeah. That's how long Barre Oster virus had,

to evolve this parasitism of grandmothers to their grandchildren.

That's, I'm not sure it's.

So does that suggest that this is not a,

this is a strategy that we don't see in, in other, in other mammals?

Or, are other examples outside of human systems where this kind of,

you know, multigenerational transmission effect happens?

There wouldn't be any reason to believe that this wouldn't be happening in

the primate alpha herpes viruses, for instance, or

the ones that happen in bovines, but I'm not sure if anyone's looked.

But, but, To find that age of.

Yeah, but the very long latent period that seemed to be quite unusual for.

Yes. For shingles, isn't it?

Because of the decades thing.

Yes. If you were a virus of a.

Mm-hm.

Of a rat or something, then being quiescent for, for

a decade wouldn't give you much bang for the bucks.

[LAUGH].

Yes, I, I agree.

There might be corollary examples in the animal kingdom, but it may be

that the humans are the most exaggerated because our lifespan is among the longest.

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