Economic case for eradicating polio: Gates Foundation

Foreign aid is a topic that a lot of Americans have questions about. Is it really helping countries lift themselves out of poverty? Is it improving people's lives or just a big waste? If it is saving a lot of lives, will that lead to overpopulation in an already-overcrowded world?

A good place to find answers to these important questions is Bill and Melinda Gates' annual letter – it gives a candid look at the impact of development aid and some of the myths that have built up around it.

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I'd like to take up a related question that people often ask me when they find out that eradicating polio is the Gates Foundation's number one priority. Is the money the world is spending to eradicate polio – about $1 billion a year – worth it? And why is it costing so much when there is barely any incidence of the disease around the world?

It's a fair question. After all, whatever money we're spending to rid the world of polio is money we aren't spending on other big health issues. So it's important to know that ending polio is a smart and cost-effective strategy.

It's also a reasonable question, especially in the United States, where polio was eliminated 35 years ago. A lot of people think we don't have to worry about it anymore. Yet, as recently as 1988, polio was still endemic in 125 countries and paralyzed 350,000 children a year. A concerted global effort over the last quarter century has cut that to just three countries where polio has never been eradicated and only 385 reported cases in 2013.

(Read more: Bill Gates: There will be no poor countries by 2035)

Polio is one of the world's most infectious diseases. For every reported case of polio paralysis, 200 people are actually infected – all of them are exposing the people around them to the disease. Last year alone, five countries that were previously polio-free had outbreaks traced to people coming from one of the three remaining countries where polio is still endemic.

Polio is also an extremely difficult disease to get rid of.About 90 percent of all children in any given community must receive multiple immunizations to wipe out the virus. No other global health effort in history has posed such a logistical challenge.

Ending polio will require an estimated $5.5 billion between 2013 and 2018. It's a substantial investment because we have to reach and vaccinate more than 250 million children multiple times every year, conduct monitoring and surveillance in more than 70 countries, and finish building a sustainable infrastructure to support routine immunization for other infectious diseases and improve maternal health..

Failing to achieve global eradication would cost far more. Mathematical models suggest that abandoning the program before eradication is achieved would result in a resurgence of polio – within a decade as many as 200,000 cases of paralysis each year .Treating those cases would cost more money in the long run. Plus, of course, the human costs of sliding backward are incalculable.

On the other hand, ending polio will free up resources that can be invested in other global efforts to reduce child mortality and end extreme poverty. Estimates show that eradicating global polio now could generate net benefits of $40-50 billion globally by 2035, with most of that savings in the poorest countries.

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The most recent example of the benefits of ending polio can be seen in India. Once considered the hardest place to get rid of polio, India just celebrated three years of being polio-free, and is now turning its sights to measles and immunizations for other diseases.

Creating a polio-free world is within our reach. Eradicating the disease will prove to be one of the smartest investments the world has ever made. And the health infrastructure we leave behind will have lasting benefits to achieve other global health goals.

Chris Elias is president of the Global Development Program at the Bill & Melinda Gates Foundation and oversees the foundation's efforts to eradicate polio worldwide.