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  • Measles is one of the most contagious diseases known to man.

  • In fact, if someone with measles coughs in an elevator, 90% of the people who use that

  • elevator after will catch the disease.

  • Unless of course you've been vaccinated.

  • Then you'll be completely fine.

  • This is the measles virus, it's been around for thousands of years and has been responsible

  • for the deaths of millions of people.

  • Now, on the surface, measles symptoms seem fairly innocuous.

  • But the real damage, the damage that can lead to death, happens on a cellular level.

  • Hi I'm Roberto Cattaneo.

  • I'm a Doctor of Philosophy and Professor of Molecular Biology at the Mayo Clinic.

  • I'm studying the measles virus since about 35 years.

  • Measles uses the trachea as a trampoline.

  • It is in the ideal position in the body to get expelled and to get aerosolized dispersed

  • in the air in small particles very efficiently.

  • When someone with measles coughs or sneezes, these droplets contain the measles virus,

  • and because measles is a respiratory disease, all someone needs to do is breathe in that

  • infected air in order to contract measles.

  • Unless, of course, they've been vaccinated.

  • When the measles virus reaches the lungs, it is met by a type of white blood cell called a macrophage.

  • Usually, macrophages seek out and destroy dangerous pathogens like viruses.

  • But the measles virus tricks the macrophage into not seeing it as a danger and instead,

  • safely transports the virus into the body's lymph nodes.

  • It's here that the virus begins to replicate and spread throughout the entire lymphatic system.

  • Yea, I mean the macrophages thinks to have a system in which they basically get rid of the virus

  • And measles can stay there.

  • So not only it is invisible but it begins to make damage to these cells.

  • The task of these cells is also to go out and fight infection,

  • but instead of fighting infection, they go out with the virus and distribute it to the body.

  • Now, as the virus starts to spread, it enters immune cells that express a protein named

  • SLAM.

  • These cells arememoryimmune cells, meaning that they remember other pathogens

  • that previously infected the host.

  • Measles attacks and kills these SLAM-expressing memory cells and once those memories of past

  • infections are erased, the body will be in a much weaker position to fight off future infections

  • This is why measles is so deadly.

  • But even though the virus has tricked your immune system to helping it, that doesn't

  • mean your immune system has given up.

  • Well, at some point the immune system will notice and will secrete cytokines and attract other immune cells.

  • So at some point the enemy will be identified and taken care of.

  • But for the viruses in fact it is only necessary to get out of the host and find a new host.

  • So it's in fact better not to kill the host.

  • That's right, it's in the best interest of the virus not to kill you, that's some other diseases job.

  • The job of the measles virus is to find a new host, which brings us to another protein

  • the virus expresses: nectin4.

  • And we discovered nectin4 as the epithelial receptor or host exit receptor for measles virus.

  • As measles spreads throughout the body, it also enters cells that express the protein nectin4.

  • This protein is expressed very preferentially in the trachea.

  • And the more the virusit replicates in the trachea, the more cells it kills there.

  • This dead cell build up actually causes the human host to cough or sneeze, helping spread

  • it into a new human host, bringing us right back to where we started.

  • Now, the good news is that once you get the measles, your body learns how to defeat it

  • and you probably won't get it again.

  • This is similar to how the vaccine works, but the difference is you're given a weaker

  • dose, so you can become immune without getting sick or damaging your immune cells.

  • So the vaccine causes the host to remain immune to measles we think for life long or almost life long time.

  • And without measles, other diseases, the ones that actually do the killing, have gone down.

  • Basically the number of hospitalization has been reduced considerably sometimes to about

  • half for several different infectious diseases.

  • So, if you haven't been vaccinated...

  • Yea, the vaccine works beautifully.

  • maybe think about it?

  • Measles may be the enemy of the immune system, but researchers, including Dr Cattaneo, are

  • working on ways to alter the measles virus so it kills cancer cells.

  • For me, a reason to continue study measles is to make it into a friend, making an old

  • enemy into a new friend by modifying it genetically.

Measles is one of the most contagious diseases known to man.

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Here's What Makes Measles So Dangerous

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    Jerry Liu   に公開 2019 年 08 月 15 日
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