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Polio epidemiology

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by Ian Mannarino.

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  • starky ultimate style avatar for user antiquark101
    why do vaccines take so long to create? is it because of the time needed to completely analyze the virus, or because of the danger of working with the virus?
    (6 votes)
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    • piceratops ultimate style avatar for user Megan Riley
      Vaccines can be difficult to create for a number of reasons. Sometimes we don't have a good animal model to test the vaccine in. Sometimes we don't know enough about the bug to understand what bits of it to include in the vaccine in order to stimulate good immunity (which parts the immune system reacts to best). In the case of some diseases, such as malaria and HIV, there aren't good natural models of immunity to base the vaccine off of, and so it's much more challenging.
      (3 votes)
  • leafers ultimate style avatar for user Stephanie Light
    "Poor access to children" makes this hard to treat/prevent, or poor access to medicine?
    (1 vote)
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    • leafers tree style avatar for user Calimie
      Keep in mind that Afghanistan has basically been at war for over 20 years, that diplomatic relations with Pakistan are sometimes difficult and that the northern part of Nigeria has been controlled by a terrorist group for quite some time now. You can't simply drop doctors with the vaccine there: it's not only an issue of difficult terrain or talking people into vaccinations. Some areas of those countries are no-go areas. Poverty didn't stop India from eradicating the virus.
      (3 votes)
  • purple pi purple style avatar for user Sal DJ
    what about war zones in the last few years like Syria and Jaman, there is not Polio cases?
    (1 vote)
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Video transcript

- (Voiceover) Polio is a very serious communicable disease that was indemic to the world prior to 1900. The first major outbreak in the United states was recorded in 1916, during which about 6000 people died, and 27000 people were left paralyzed. So, before vaccinations were wide spread and used in the United States, this was a very serious disease and was spread very easily from person to person. Now, infections seem to peak in the summer months, in temperate climates, so in places like the United States, it was noticed that during these summer months there were a larger number of Polio outbreaks. However, in tropical areas, such as South America or India, there was really no seasonal variability. So, it just seems with Polio, outbreaks occur more in hotter climates. Now, this might be due to the fact that the Polio virus was able to replicate in warmer temperatures a little bit more. But also, increased use of water during hot months and decreased sanitation allows the spread of the Polio virus. Now, Polio mainly affects children under the age of five years old, and most commonly affects infants. So, in hot summer months when children are trying to go to swimming pools, the virus can be really easily spread from person to person. And, the virus is spread, most commonly, through the fecal to oral route. So, any children that doesn't have proper sanitation, if they don't clean themselves properly after going to the bathroom, can easily spread it from one person to the next. However, there are some cases of transmission from mouth to mouth, so oral to oral transmission. And, the disease is highly infectious. In fact, children infected by the virus can actually carry it for up to seven to ten days before they even display any symptoms whatsoever, and be infectious for up to six weeks after becoming initially infected. Now, thankfully, 90 to 95 percent of people never experience any symptoms whatsoever. But, they can still spread the disease and that's why it makes it extremely difficult to eradicate the Polio virus from the world. Because, an infected individual can pass it to somebody else without ever knowing that they were infected. So, it's extremely hard to track on a global scale. Now, though all of this makes eradication efforts very challenging, thankfully there is one glimmer of hope. Transmission is only from human to human. The virus cannot be passed from animal to human or human to animal. So, in other words, humans are the only reservoir for the Polio virus. This has been a huge help when eradication efforts started around 1988. In fact, as you seen in this graph of the global Polio virus incidents, you can see that cases hovered around 350,000, but have dropped since vaccinations have been used across the globe. In fact, in 2013, there were only a total of 416 new cases reported in the world. Now, in the western hemisphere, the Polio virus is a thing of the past. Polio was eradicated almost entirely from the United States in 1979. The last cases reported in the western hemisphere occurred in Peru, around 1991. Unfortunately, there are still cases that do exist. As of 2014, there are only three countries that remain Polio endemic, that includes Pakistan, Afghanistan, and Nigeria. You can see that these are all very tropical, warm climates, so it's easier for the virus to spread in these areas. Polio was also recently eradicated from India in 2011. However, despite all of this success in the Polio eradication through the widespread use of vaccination, this is still a global emergency. With modern technology and with the ability for people to fly from one area of the world to another, you can see why this can be such a global concern and such a threat to the population of the world. So, what's the strategic plan? The World Health Organization is focusing on both vaccinations and surveillance, trying to keep track of cases in the world so that they can properly eradicate Polio from the world, forever. Improving sanitation is another major effort that can lead to less infants being exposed to the Polio virus. Unfortunately, there are still many obstacles to overcome. Poor access to children in impoverished areas such as Afghanistan and Pakistan, as well as Nigeria, make it very challenging to stop this virus in it's track. But, through collaborative efforts by many different organizations in the world, hopefully soon, Polio can be eradicated completely and become a thing of the past.