very real.

And while rare, cases of it do occur all over the world each year.

So let’s confront this villain head-on and flesh it out.

Thank you for coming.

Hi, my name is Isaac Chiu.

I'm an assistant professor at Harvard Medical School in the Department of Immunology.

I'm very interested in understanding how pathogens interact with the immune system and in this

case, in highly invasive infections such as flesh-eating disease.

Flesh-eating bacteria is more commonly known as a necrotizing infection.

This cell death of the body’s soft tissue is called necrotizing fasciitis, and you can

get the types of bacteria that cause it in a few different ways.

So you could get necrotizing fasciitis from a bacteria that came in from an insect bite

or from a wound.

Maybe you had an opening in your skin and you stepped in brackish water.

So there are many ways which bacteria can get in.

And one of the main types of those bacteria that causes this disease is from the same

family as a common infection we all know and have maybe even had—strep.

Six hundred million people a year get strep throat, but that same pathogen can also in rare cases

cause necrotizing fasciitis, but it's the same pathogen.

The leading cause is streptococcus pyogenes, but it can also be caused by both gram-positive

and gram-negative types of bacteria, including staph aureus and vibrio.

And some actually are polymicrobial so there are several bacterias together that form these

necrotizing invasions.

So a big question is how does the bacteria become aggressive and dangerous, causing this

invasive type of soft tissue infection?

When it gets into that person in that situation, that its tissue environment sends

a signal to that bacteria that makes it switch on genes that are making it more virulent?

Is it that individual that's more susceptible to infection and that's why it's become necrotizing

fasciitis?

These are important questions.

And while necrotizing fasciitis is still rare, fewer than about one in 100,000 adults will contract

it, certain people are more susceptible to it.

Some risk factors include diabetes and compromised immune systems.

And with a mortality rate of up to about 30% in the U.S. and higher in developing nations, it's a dangerous

disease no matter where you live. Not to be alarmist, but I think it's definitely

important to watch for symptoms of infection generally to get that treated.

But it's very, very rare.

When it does infect the body, it can spread quite rapidly, invading the deeper tissues.

This happens when blood flow becomes blocked, destroying the soft tissue.

It can occur in our limbs and groin areas, and that’s how it gets its name flesh eating.

One of the major characteristic of flesh-eating disease is pain.

So pain out of porportion with other clinical manifestations

This could be a sign of potential necrotizing fasciitis.

Once this bacteria makes its way down to the deep tissues, you may not see the superficial signs

you’d see with a normal infection, such as redness or swelling.

But you would experience an extreme amount of pain.

This “pain out of proportion” is a red flag for a possible flesh-eating disease.

One of the ways unfortunately to treat this disease

is to surgically remove the tissue or even to amputate the limb to prevent the bacteria

from getting further than it can go, as well as IV antibiotics.

So I think one of the points is that it's hard to treat because it's so aggressive.

Potentially if you treat it earlier on with antibiotics or surgical removal, their survival

rate will be better.

And normally, an infected site would be full of white blood cells like neutrophils, which

help trigger inflammation and send a signal that something is wrong.

Neutrophils are kind of the white blood cell army.

They're mobilized during infection.

They're circulating in our blood and they hone into the tissues as soon as there's infection,

but they're not able to get to the necrotizing fasciitis lesions very efficiently and they're

silenced by the bacteria as well through toxins.

If you look inside a necrotizing fasciitis tissue, you don't see that many immune cells.

That's one of the contributing factors because the bacteria has found a way to evade the

immune system.

But there is hope on the horizon, including treatments that can block the bacteria from

invading as efficiently and even the use of a common cosmetic treatment.

So we have found, for example, by using botulinum toxins or Botox, you can silence the nerves

from releasing these anti-immune molecules called CGRP.

So this is effective because we found that the nerves block neutrophils, the immune cells

that are really important for fighting infections.

So by blocking that with Botox, neutrophils come in to fight the bacteria at that site.

So these are areas we're really excited about pursuing to slow down this bacterial

spread during necrotizing invasion.

While flesh-eating bacteria and infection are rare, it’s important to know the signs

and seek medical attention if you’re concerned.

I think the point is that you just should

see a doctor if you have, like, any infections... period.

So the key is to go early and get it treated.