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  • In 2008, something incredible happened: a man was cured of HIV.

  • In over 70 million HIV cases, that was a first and, so far, a last.

  • We don't yet understand exactly how he was cured.

  • We can cure people of various diseases, such as malaria and hepatitis C,

  • so why can't we cure HIV?

  • Well, first let's examine how HIV infects people

  • and progresses into AIDS.

  • HIV spreads through exchanges of bodily fluids.

  • Unprotected sex and contaminated needles are the leading cause of transmission.

  • It, fortunately, cannot spread through air, water, or casual contact.

  • Individuals of any age, sexual orientation, gender and race

  • can contract HIV.

  • Once inside the body, HIV infects cells that are part of the immune system.

  • It particularly targets helper T cells,

  • which help defend the body against bacterial and fungal infections.

  • HIV is a retrovirus,

  • which means it can write its genetic code into the genome of infected cells,

  • co-opting them into making more copies of itself.

  • During the first stage of HIV infection,

  • the virus replicates within helper T cells,

  • destroying many of them in the process.

  • During this stage, patients often experience flu-like symptoms,

  • but are typically not yet in mortal danger.

  • However, for a period ranging from a few months to several years,

  • during which time the patient may look and feel completely healthy,

  • the virus continues to replicate and destroy T cells.

  • When T cell counts drop too low,

  • patients are in serious danger of contracting deadly infections

  • that healthy immune systems can normally handle.

  • This stage of HIV infection is known as AIDS.

  • The good news is there are drugs that are highly effective

  • at managing levels of HIV

  • and preventing T cell counts from getting low enough for the disease to progress to AIDS.

  • With antiretroviral therapy,

  • most HIV-positive people can expect to live long and healthy lives,

  • and are much less likely to infect others.

  • However, there are two major catches.

  • One is that HIV-positive patients must keep taking their drugs for the rest of their lives.

  • Without them, the virus can make a deadly comeback.

  • So, how do these drugs work?

  • The most commonly prescribed ones prevent the viral genome from being copied

  • and incorporated into a host cell's DNA.

  • Other drugs prevent the virus from maturing or assembling,

  • causing HIV to be unable to infect new cells in the body.

  • But HIV hides out somewhere our current drugs cannot reach it:

  • inside the DNA of healthy T cells.

  • Most T cells die shortly after being infected with HIV.

  • But in a tiny percentage,

  • the instructions for building more HIV viruses lie dormant,

  • sometimes for years.

  • So even if we could wipe out every HIV virus from an infected person's body,

  • one of those T cells could activate and start spreading the virus again.

  • The other major catch is that not everyone in the world has access to the therapies that could save their lives.

  • In Sub-Saharan Africa, which accounts for over 70% of HIV patients worldwide,

  • antiretrovirals reached only about one in three HIV-positive patients in 2012.

  • There is no easy answer to this problem.

  • A mix of political, economic and cultural barriers

  • makes effective prevention and treatment difficult.

  • And even in the U.S., HIV still claims more than 10,000 lives per year.

  • However, there is ample cause for hope.

  • Researchers may be closer than ever to developing a true cure.

  • One research approach involves

  • using a drug to activate all cells harboring the HIV genetic information.

  • This would both destroy those cells and flush the virus out into the open,

  • where our current drugs are effective.

  • Another is looking to use genetic tools

  • to cut the HIV DNA out of cells genomes altogether.

  • And while one cure out of 70 million cases may seem like terrible odds,

  • one is immeasurably better than zero.

  • We now know that a cure is possible,

  • and that may give us what we need to beat HIV for good.

In 2008, something incredible happened: a man was cured of HIV.

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B1 US TED-Ed hiv cure hiv positive infected healthy

【TED-Ed】Why it’s so hard to cure HIV/AIDS - Janet Iwasa

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    稲葉白兎 posted on 2015/07/12
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