But what started out as a celebration led to a health crisis:

just a few days after the pilgrimage, more than 2,000 cases of meningitis

broke out spreading across Saudi Arabia and the rest of the world.

The outbreak was so fierce that it was believed to have sparked a wave of deadly meningitis

epidemics that ultimately infected tens of thousands of people worldwide.

Meningitis is the inflammation of the meninges, three tissue layers responsible

for protecting the brain and spinal cord. What makes meningitis so dangerous compared

to other diseases is the sheer speed with which it invades a person's body.

In the worst cases, it causes death within a day. Fortunately, that's rare

for patients who receive early medical treatment.

The disease primarily comes in three forms:

fungal, viral, and bacterial-- the last being the most deadly by far,

and what we'll focus on.

People usually contract bacterial meningitis by breathing in tiny particles

of mucus and saliva that spray into the air when an infected person sneezes or coughs.

It can also be transmitted through kissing, or sharing

cigarettes, toothbrushes or utensils. Some people can be infected and carry the

disease without showing symptoms or getting sick, which helps the disease

spread quickly to others.

Once the bacteria enter the nose, mouth, and

throat, they cross the surrounding membranes and enter the bloodstream.

From there, bacteria have rapid access to the body's tissues--including a membrane

called the blood-brain barrier. This is made of a tight mesh of cells which

separate blood vessels from the brain, and block everything except for a specific

set of particles, including water molecules and some gasses. But in ways

that scientists are still trying to understand, meningitis bacteria can trick

the barrier into letting them through.

Inside the brain, the bacteria swiftly infect the meninges.

This triggers inflammation as the body's immune response

kicks into overdrive, bringing on fever and intense headaches. As swelling in the

meninges worsens, the neck begins to stiffen. Swelling in the brain disrupts its

normal function--causing symptoms like hearing loss and extreme

light sensitivity. As pressure increases in the cranium, it may also make the

person confused--one of the hallmarks of the disease.

A few hours in, the rapidly multiplying bacteria start to release toxins,

leading to septicemia,

also known as blood poisoning. This breaks down blood vessels,

letting blood seep out and form what starts out looking like a rash, and

evolves into big discoloured blots beneath the skin. At the same time, those toxins

burn through oxygen in the blood, reducing the amount that gets to major organs like

the lungs and kidneys. That increases the chance of organ shut down--and alongside

spreading septicemia, threatens death.

That all sounds scary, but doctors are so

good at treating meningitis that a visit to the hospital can drastically reduce an

adult's risk of dying from it. The longer it's left untreated, though, the more

likely it will lead to lasting damage. If declining oxygen levels cause cell

death in extreme parts of the body--like fingers, toes, arms and legs--the risk

of amputation goes up. And if bacterial toxins accumulate in the brain and trigger

cell death, meningitis could also cause long-term brain damage and memory loss.

So fast treatment, or better yet, prevention, is critical.

That's why most countries have vaccines that defend

against the disease in its deadliest forms.

Those are usually given to the people who are most at risk--like young children,

people with weak immune systems, or people who gather in large groups where an

outbreak of meningitis could potentially happen.

In addition to those gatherings,

meningitis is most common in a region called the meningitis belt that stretches

across Africa, though cases do happen all over the world. If you're concerned that

you or someone you know may have meningitis, get to the doctor as soon as

possible; quick action could save your life.