Welcome back to The Deep Dive.
Today we're tackling a really important topic,
emerging and re -emerging infectious diseases.
It kind of forces us to accept we're in this constant race, this arms race, against microbes.
It really is, and it's absolutely vital knowledge for anyone heading into healthcare.
The history here is pretty wild, too.
I mean, for ages, infectious diseases just hammered human lifespans.
Yeah, you think about things like the plague, smallpox.
People knew they spread, even if they didn't know how, scientifically speaking.
Exactly.
Then, you know, science progresses, we get vaccines, antibiotics, and maybe a bit too much confidence.
A bit.
That famous comment from the U .S.
Surgeon General William H.
Stewart back in the late
60s, saying we could basically close the book on infectious disease.
Oh, yeah.
That one hasn't aged well, has it?
Such a classic bit of irony now.
And worse, that kind of thinking actually led some big pharma companies to, well, shift focus away from new antimicrobials.
They figured the fight was won.
Right.
Okay, let's unpack this then.
Our mission today is to figure out why that book absolutely did not close.
We need to get clear on what's emerging versus re -emerging, look at the factors driving all this, and see what the global plan is to handle it.
Sounds good.
So, definitions first.
We usually split these into two main types.
First, emerging infectious diseases, or EIDs.
These are either totally new bugs identified in people, or maybe old ones that have suddenly changed their act.
Changed how?
Like, showing up more often, or they're predicted to spike soon.
And these can be anything, viruses, bacteria, fungi, parasites, you name it.
Okay, so that's the new stuff.
What about the ones we thought we'd beaten?
Right, those are the re -emerging infectious diseases, RIDs.
These are the old foes, diseases we knew about, maybe even had under control for a while, but now they're back.
Think TB, malaria.
And for either type, emerging or re -emerging, it generally happens in two steps.
First, the pathogen gets introduced into a new group of hosts.
Second, it has to establish itself and start spreading.
We sometimes call that second part adoption.
Okay, introduction and adoption.
But microbes are always changing, adapting.
So why does it feel like these introductions and adoptions are happening so much now?
Sounds like, well, like, it's mostly us, human activity.
It absolutely is, yeah.
It's this really tangled web of factors, not just one thing, but a huge one to start with.
Human demographics and behavior.
You mean people moving to cities, urbanization.
Exactly.
This massive rapid shift from rural to urban living.
The scale is incredible.
Back in 1950, maybe 29 % of people lived in cities.
By 2050, the UN thinks it'll be pushing 70%.
Wow.
And when you pack people together like that, transmission just gets way easier.
An infection that might have just sputtered out in a small rural place can suddenly hit a huge population and then, boom, travel globally through transport networks, highways, planes.
And it's not just the big picture city living, is it?
It's the day -to -day stuff, too.
Smallest things we might not even think about.
Oh, definitely.
Think about child care centers.
They become these little hot spots, right?
Diseases spread super fast among kids who then take them home to their families.
Also, we're living longer, which is great, but it means more older people whose immune systems might be a bit weaker,
more susceptible.
It's quite something.
That global connection we love flying anywhere in a day, it basically wipes out geographic barriers for pathogens, too.
Which brings us to international travel and commerce.
Yeah, this is a really big one.
We're basically giving these microbes first -class tickets around the world.
Historically, think yellow fever.
It came to the Americas on slave ships along with its mosquito vector more recently.
1967, the Marburg virus.
It showed up in Germany because of imported African green monkeys, infected the lab workers before they even knew what hit them.
And that risk is still there, especially with diseases carried by vectors like mosquitoes.
The source material highlights yellow fever again if it moves from the African savannas into urban areas there.
Then it's just a plane ride away from, say, the southern US, where the right mosquito vector is already waiting.
It's a real possibility.
Scary.
And this jump from animals to humans seems critical.
You mentioned monkeys, but how often does that happen?
It's incredibly common.
Get this.
Almost 70 % of all emerging infectious disease events in the last 10 years or so have been zoonotic.
70%, wow.
Yeah, meaning they originated in animals.
So when we mess with ecosystems, move animals around for trade, we're basically opening doors for these pathogens to jump species.
That 70 % figure really sticks with you.
Okay, shifting gears a bit.
We also have to talk about the microbes themselves, their ability to change.
Microbial adaptation and change, they evolve so fast, don't they?
Way faster than us because they reproduce so quickly.
Influenza, the flu virus, is kind of the classic example here.
We see two main ways it changes, especially these RNA viruses.
First is antigenic drift.
That's the slow, steady change, right?
Little tweaks to the virus's outer coat proteins over time.
Exactly, just small changes.
It means the antibodies you made from last year's flu or last year's shot might not recognize this year's version perfectly.
That's why you need that annual flu shot.
Okay, so drift is subtle, but then there's antigenic shift.
That sounds more dramatic.
Oh, it is.
Shift is the really big one, the one that can cause pandemics.
How does that work?
It's basically a major genetic remix.
Imagine two different flu viruses, maybe one from a bird and one from a human infecting the same cell.
They can swap large chunks of their genetic material, creating a totally new hybrid virus.
Ah, I see.
And our immune systems have never seen anything like it.
Precisely.
It bypasses any existing immunity in the population because its surface proteins are completely novel.
The 2009 H1N1 pandemic, that virus was a mix of swine, bird, and human flu genes.
And we kind of help this process along, don't we, with antibiotic overuse?
We absolutely do.
Using antimicrobials too much or when they're not needed creates this intense pressure.
It selects for bugs that happen to have resistance leading to these multidrug resistant strains.
It's a huge problem.
A self -inflicted wound, really.
Okay.
And the last big factor you mentioned was when our own systems fail us, breakdown of public health measures.
Yeah, simple things sometimes, like if sanitation systems fail or water treatment isn't adequate, you can see cholera pop back up and sadly dips in vaccination coverage.
We've seen that recently, haven't we?
With measles coming back in places like the U .S., even though it was declared eliminated, all linked to unfounded fears about vaccines.
Exactly.
A real tragedy because it's so preventable.
So, okay, knowing these things can happen, these breakdowns and adaptations,
how do public health folks categorize these threats to, you know, manage the response effectively, like the NIAA?
Right, the National Institute of Allergy and Infectious Diseases.
They have a system that helps coordinate things.
Yeah, they break it down into three main groups, which is pretty useful.
Group one is the really new stuff pathogens only recognized in the last couple of decades.
Think HIV AIDS, Ebola when it first emerged.
Okay.
Group two are the re -emerging ones we talked about, TB, malaria, those old enemies making a comeback.
Got it.
And group three?
Group three is interesting.
It's agents that have bioterrorism potential.
Now that's often covered separately, but NIAA includes it here to make sure preparedness covers all the ways a dangerous pathogen might emerge, whether naturally or deliberately.
It clarifies the response needed.
Makes sense.
So given this constant churn of new and returning threats, what's the actual public health game plan?
If we can't just close the book, how do we defend ourselves, especially here in the U .S.?
Well, the CDC, the Centers for Disease Control and Prevention, is the lead agency for the U .S.
Their approach really boils down to three core actions.
Okay, what's step one?
Surveillance.
This is absolutely key.
It's the constant watching, collecting data on specific nationally notifiable diseases from state and local health departments.
So just tracking numbers.
It's more than that.
Often detection isn't just a number hitting a threshold.
It's sharp epidemiologists noticing a weird cluster of illnesses that don't quite fit, like with hantavirus back in 93, or spotting drug resistance where it wasn't expected.
Okay, so surveillance flags a potential problem.
Then what?
Step two, investigation.
Once something unusual pops up, you have to move fast, identify the pathogen, figure out how it's spreading, find the source.
That sounds like a lot of different skills needed.
It is.
It takes epidemiology, lab work, environmental checks, talking to people.
The CDC has centers specifically designed to support public health labs across the country, making sure they can do this rapid testing and detective work.
And once you know what you're dealing with.
Step three, response.
This is putting the control measures into action.
Could be launching vaccination campaigns, controlling mosquitoes or rodents, recalling contaminated food, or in really serious situations using isolation or quarantine, plus getting good information out to the public.
But you said earlier these bugs travel globally in days.
So a U .S.
only response isn't enough, is it?
Not at all.
U .S.
health is totally tied to global health now.
That's where the international health regulations, the IHR come in.
They were updated significantly back in 2005.
IHR.
That's like the global rulebook for this stuff.
Pretty much.
Yeah.
It's the framework that pushes countries to prevent, detect and report public health emergencies that could cross borders.
It's about transparency and international cooperation.
So everyone's supposed to work together.
That's the goal.
It means one country doesn't have to face a major outbreak alone.
And the CDC plays a big role globally, too, through its International Emerging Infections Program, or IEIP.
They work in several key areas, including building this global network of networks for surveillance.
A global network of networks.
I like that.
So it's not just one country reporting.
It's multiple systems potentially catching a signal early.
Exactly.
A web of monitoring.
Yeah.
And this global presence also creates vital research chances.
Like the source mentioned the 2014 Ebola outbreak when those two infected American health care workers were brought back to Emory University.
That was obviously scary, but it gave researchers an unprecedented chance to study Ebola up close in a top -notch containment facility.
What they learned helped the global fight against the disease.
It turned a crisis into a research opportunity.
Right.
This really highlights how dynamic this all is.
We've gone from tiny changes in flu viruses that drift all the way to huge societal shifts like urbanization and the absolute need for global teamwork with things like the IHR and IEIP.
Yeah.
And I think the big takeaway for you, for anyone listening, especially if you're heading into health care, is that knowledge is really your best weapon here.
These diseases are always emerging, always reemerging.
Remember that 70 percent zoonotic figure.
And it means the job isn't just treating what we already know.
It's about being ready, anticipating, adapting to these new threats that keep evolving because of, well, us and the incredible adaptability of microbes.
A constant challenge for sure.
And one we'll definitely keep an eye on.
Thanks so much for walking us through this today.
My pleasure.
And thanks to all of you for being part of our last minute lecture family.
We'll catch you on the next deep dive.