Photo: Sari Dennise

There is a big difference between eradication and elimination when it comes to diseases. Disease eradication is when the global number of cases reaches zero. Even if there is a vaccine available for a specific disease, eradication means no one will ever be in need of using that vaccine again. Elimination is not as stringently defined – it can refer getting rid of the disease in specific regions or diminishing the cases to a negligible number of unlucky and impoverished people.

There have been a total of seven global attempts to eradicate human diseases. 4 failed (hookworm, malaria, yaws, and yellow fever), 2 are ongoing (polio and guinea worm), and only 1 was successful (smallpox).

Smallpox
In the early 1950s roughly 50 million people a year contracted smallpox with a mortality rate north of 10%. Shockingly, only 30 years later the disease was declared completely eradicated.

The first vaccine for smallpox was discovered in 1796. By giving someone the similar cowpox virus, they were then immune from contracting smallpox (fun fact: the word vaccine has the Latin root vaccinus meaning of or from cows). Unfortunately this was before the advent of FedEx so a timely delivery of the vaccine all over the world was not possible. Thus, the disease persisted for another 170 years.

In the 1950s and 60s a global initiative to eradicate smallpox began. Any outbreaks were immediately quarantined and everyone who lived close by received a vaccination (I imagine it was just like the movie “Outbreak”). Why did it take over 170 years from known vaccination to complete eradication? It was as much a communication and education initiative as a medical one. Any outbreaks of smallpox had to be immediately identified and a quick response was necessary to keep it from spreading. This was simply not possible in the 1800s.

Polio and guinea worm
There is currently an initiative to eradicate two more diseases from the face of our planet. Polio has been eliminated from everywhere but the poorest countries – there are now less than 2000 cases per year.

Guinea worm is slightly different than the other diseases – it is not transmitted from person-to-person and there is no vaccine. It is spread through drinking water that is not clean – currently only 4 countries still have water that contains the disease.

What is next?
There are a number of diseases that have been eliminated from most of the world and are in consideration for complete eradication. Malaria, measles, yaws, leprosy, rubella, lymphatic filariasis, and onchocerciasis are all on the list. The decision to eradicate a disease or not is difficult – is it worth the economic and time resources to pursue when the disease does not threaten the general public health?

What else is interesting?
US and Russia have not in fact destroyed the last remaining smallpox samples and they are still used in laboratories. Even though no human has smallpox, it is still possible for the vials to be released and reintroduce the disease. The destruction of these last remaining samples is called disease extinction and is the final step in the process.

The most important take away from this is that you do not need to be a doctor to make a difference in disease eradication. The hard part is not diagnosing what disease a person has. What is difficult is educating the at risk population and making vaccines available in the poorest, most remote regions of the world.

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Bill Gates’ work on eradicating malaria is what piqued my interest. He gave an interesting TED talk on disease and education.