Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
NOVA Home Find out what's coming up on air Listing of previous NOVA Web sites NOVA's history Subscribe to the NOVA bulletin Lesson plans and more for teachers NOVA RSS feeds Tell us what you think Program transcripts Buy NOVA videos or DVDs Watch NOVA programs online Answers to frequently asked questions
Killer Disease on Campus

Killer in the Bloodstream

 

Even people familiar with meningococcal disease are astonished at the rapidity with which this rare though deadly illness can ravage the body. Within hours, patients can go from perfectly healthy to mortally ill. What makes these microbes so lethal? In this animated feature, follow the progression of meningococcal bacteria as they race through the bloodstream, wreaking havoc on a scale few diseases can match with such lightning speed.—Peter Tyson


Assaulting the body

Step 1

watch video in a new window via:
QuickTime
RealVideo dialup
RealVideo broadband



 

Meningococcal bacteria can cause two life-threatening conditions: meningitis and sepsis.

In meningitis, the bacteria attack the lining around the brain called the meninges. They breach the meninges to infect the fluid running into the spinal cord. One clear, early symptom is a stiff, sore neck. The meninges and brain start to swell, putting pressure on essential nerves. Fewer than one in 50 victims of meningococcal meningitis will die, but survivors are often left deaf or with permanent brain damage.

The other type of infection is much more deadly, killing roughly 20 percent of its victims. It's a severe blood poisoning called meningococcal sepsis that affects the entire body. The bacterial toxins rupture blood vessels and can rapidly shut down vital organs.




Entering the throat

Step 2

watch video in a new window via:
QuickTime
RealVideo dialup
RealVideo broadband



 

Meningococcal bacteria commonly live in the human throat without causing harm. But sometimes they break through the throat's lining and enter the bloodstream. The reasons why and how are only now being unraveled. Damage to the throat from flu and other infections could be one factor.




Hurtling through the bloodstream

Step 3

watch video in a new window via:
QuickTime
RealVideo dialup
RealVideo broadband



 

Every meningococcal bacterium is surrounded by a slimy outer coat that contains a poisonous chemical called an endotoxin. While many bacteria produce endotoxin, the levels produced by meningococcal bacteria are 100 to 1,000 times greater than normal.

As the bacteria multiply and move through the bloodstream, they shed bubbles that contain concentrated amounts of toxin. These bubbles also act as decoys, confusing the body's immune system. The endotoxin targets the heart, affecting its ability to pump and also causes blood vessels throughout the body to leak. As every vessel starts to hemorrhage, major organs like the lungs and kidneys are damaged and eventually destroyed.

Two things can stop this runaway infection before the patient dies: antibiotics like penicillin, and the patient's own immune system.




Attacked by antibiotics

Step 4

watch video in a new window via:
QuickTime
RealVideo dialup
RealVideo broadband



 

As soon as doctors suspect meningococcal disease, patients are given a large dose of antibiotic, usually penicillin. Penicillin flowing through the bloodstream rapidly kills the bacteria. But it cannot penetrate the bubbles that contain the endotoxin. In fact, as the bacteria are killed, they release even more toxin. It takes up to two days for the poison to be cleared from the body and the siege to end.




Killing tissue

Step 5

watch video in a new window via:
QuickTime
RealVideo dialup
RealVideo broadband



 

As soon as the bacteria entered the bloodstream, unleashing the poisonous endotoxin, the body began responding on its own. White blood cells, the hunter-killers of the immune system, locked onto the bacteria, engulfing them and coming into contact with the endotoxin.

The poison causes the white cells to release chemicals that make the blood vessel walls sticky. The white cells then become trapped on the walls, leaving a trail of damage. Gradually the lining of the blood vessels is stripped away. And as the damage increases, the vessel walls break up and pieces fall off. The blood's repair cells, called platelets, rush to plug up the damaged areas.

Dangerous clots begin to form. The proteins that normally prevent clotting have all been destroyed. Within minutes the small blood vessels of the body are completely blocked. The damaged blood vessels disintegrate, and blood and other fluids hemorrhage into the surrounding tissue. It is this cascade of events that causes the distinctive rash that appears beneath the skin and kills tissue throughout the body.





Killer Disease homepage


Other Life Cycles

See HIV in Action See HIV in Action
Follow the virus that causes AIDS as it invades cells.

The Dope on Nicotine
Trace the route of nicotine through the brain.




Companion Web Site Content
Amy's Story

Amy's Story
Meet a 17-year-old survivor of meningococcal disease.

Behind the Scenes

Behind
the Scenes

What it was like to film life-or-death situations.

Amy's Story

Killer in the
Bloodstream

Animations of meningococcal bacteria at work.

Making Vaccines

Making Vaccines
Create six vaccines in our virtual laboratory.



Send feedback Image credits
   
NOVA Home Find out what's coming up on air Listing of previous NOVA Web sites NOVA's history Subscribe to the NOVA bulletin Lesson plans and more for teachers NOVA RSS feeds Tell us what you think Program transcripts Buy NOVA videos or DVDs Watch NOVA programs online Answers to frequently asked questions

Support provided by

For new content
visit the redesigned
NOVA site