Why is meningitis so dangerous? - Melvin Sanicas

3,007,306 views ・ 2018-11-19

TED-Ed


Please double-click on the English subtitles below to play the video.

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In 1987, tens of thousands of people
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gathered in Saudi Arabia for the annual Hajj pilgrimage.
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But what started out as a celebration led to a health crisis:
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just a few days after the pilgrimage,
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more than 2,000 cases of meningitis broke out
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spreading across Saudi Arabia and the rest of the world.
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The outbreak was so fierce
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that it was believed to have sparked a wave of deadly meningitis epidemics
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that ultimately infected tens of thousands of people worldwide.
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Meningitis is the inflammation of the meninges,
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three tissue layers responsible for protecting the brain and spinal cord.
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What makes meningitis so dangerous compared to other diseases
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is the sheer speed with which it invades a person’s body.
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In the worst cases, it causes death within a day.
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Fortunately, that’s rare for patients who receive early medical treatment.
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The disease primarily comes in three forms:
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fungal, viral, and bacterial-- the last being the most deadly by far,
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and what we’ll focus on.
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People usually contract bacterial meningitis by breathing in
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tiny particles of mucus and saliva that spray into the air
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when an infected person sneezes or coughs.
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It can also be transmitted through kissing,
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or sharing cigarettes, toothbrushes or utensils.
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Some people can be infected and carry the disease
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without showing symptoms or getting sick,
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which helps the disease spread quickly to others.
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Once the bacteria enter the nose, mouth, and throat,
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they cross the surrounding membranes and enter the bloodstream.
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From there, bacteria have rapid access to the body’s tissues
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--including a membrane called the blood-brain barrier.
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This is made of a tight mesh of cells which separate blood vessels from the brain,
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and block everything except for a specific set of particles,
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including water molecules and some gases.
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But in ways that scientists are still trying to understand,
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meningitis bacteria can trick the barrier into letting them through.
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Inside the brain, the bacteria swiftly infect the meninges.
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This triggers inflammation as the body’s immune response kicks into overdrive,
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bringing on fever and intense headaches.
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As swelling in the meninges worsens, the neck begins to stiffen.
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Swelling in the brain disrupts its normal function--
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causing symptoms like hearing loss and extreme light sensitivity.
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As pressure increases in the cranium, it may also make the person confused--
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one of the hallmarks of the disease.
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A few hours in, the rapidly multiplying bacteria start to release toxins,
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leading to septicemia, also known as blood poisoning.
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This breaks down blood vessels,
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letting blood seep out and form what starts out looking like a rash,
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and evolves into big discoloured blots beneath the skin.
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At the same time, these toxins burn through oxygen in the blood,
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reducing the amount that gets to major organs like the lungs and kidneys.
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That increases the chance of organ shut down
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--and alongside spreading septicemia, threatens death.
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That all sounds scary, but doctors are so good at treating meningitis
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that a visit to the hospital can drastically reduce an adult’s risk of dying from it.
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The longer it’s left untreated, though,
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the more likely it will lead to lasting damage.
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If declining oxygen levels cause cell death in extreme parts of the body
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--like fingers, toes, arms and legs-- the risk of amputation goes up.
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And if bacterial toxins accumulate in the brain and trigger cell death,
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meningitis could also cause long-term brain damage and memory loss.
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So fast treatment, or better yet, prevention, is critical.
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That's why most countries have vaccines that defend against the disease
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in its deadliest forms.
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Those are usually given to the people who are most at risk--like young children,
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people with weak immune systems, or people who gather in large groups
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where an outbreak of meningitis could potentially happen.
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In addition to those gatherings,
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meningitis is most common in a region called the meningitis belt
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that stretches across Africa, though cases do happen all over the world.
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If you’re concerned that you or someone you know may have meningitis,
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get to the doctor as soon as possible;
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quick action could save your life.
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