The Eradication of Diseases

Podcast Transcript

The largest single killer of human beings throughout history has been disease.

With the advent of modern medicine and the understanding of how bacteria, viruses, and parasites work, we’ve made enormous strides in reducing incidents of disease.

In a few cases, we have completely or almost completely eradicated diseases from the Earth.

Learn more about humanity’s attempt to eradicate diseases on this episode of Everything Everywhere Daily.

To say that disease has devastated humanity is almost an understatement.

Much of history has been written by the impact that disease has had on human populations. I’m sure you are familiar with pandemics such as the black death which killed as many as 50% of the population in Eurasia.

I’ve done an episode on the Plague of Justinian, which wreaked havoc on the ancient world around the Mediterranean. The Spanish Flu killed an estimated 50 million people a century ago.

In between all those pandemics, there were cases of smallpox, malaria, cholera, tapeworm, hookworm, various flues, fevers, and other diseases which were the primary reason why human life expectancy was so low for so long.

As the germ theory of disease developed, we developed techniques for treating and preventing disease. Oftentimes, eliminating disease required little more than providing clean water.

Sometimes, it required novel treatments such as antibiotics like penicillin.

There were a few diseases, where there was potential to completely eliminate them from the face of the Earth. Some diseases can’t ever really be eliminated because they exist in nature. We can suppress them through good hygiene, but they can’t really be eradicated.

Other diseases, however, are only spread from person to person. If we can break the links between people to stop the transmission, it is possible, in theory, to end such diseases once and for all.

The first such disease and perhaps the most famous example of complete eradication is smallpox.

Smallpox was really really bad. I’ve done an entire episode on smallpox so I won’t belabor the point here, but smallpox probably killed more people than anything else in the 100 years prior to its eradication. One estimate I’ve seen is that from the late 19th through the 20th century, smallpox might have killed half a billion people.

Because smallpox was spread from person to person, eradication was possible. The idea of eradicating smallpox began after the second world war. Coordinated efforts existed to not only vaccinate people for smallpox but to fly into places where there were outbreaks to quarantine people and do contact tracing.

The last case of smallpox was documented in 1977 in Somalia, and it was declared eradicated in 1980.

There is one other disease that has been totally eradicated: Rinderpest.

Rinderpest isn’t as well known as smallpox, mainly because it doesn’t infect humans. It is a measles-like virus that primarily affected cattle. Transmission of the virus was usually through direct contact and contaminated water.

The last confirmed case of Rinderpest occurred in Kenya in 2001, and it was declared eradicated by the World Health Organization in 2011.

So far, these are the only two diseases for which there has been a declaration of complete eradication.

However, they are not the only diseases where eradication efforts are underway. We are getting very close on a number of fronts with other diseases.

The disease which might be next on the eradication list is probably polio.

Polio is a disease that can often result in paralysis, including the paralysis of the muscles which allow you to breathe. This would often result in people having to spend their lives in an iron lung, as they couldn’t breathe on their own. In extreme cases, it resulted in death.

The war on the poliovirus started in the 1950s with the development of the first polio vaccine by Dr. Jonas Salk. It made him a celebrity and caused polio rates to plunge.

The last case of polio in the United States occurred in 1979.

With so much progress already made, the announcement of a global polio eradication program was made in 1988 by the WHO and other international organizations.

The initial goal was to eradicate polio by the year 2000, however, that hasn’t quite happened. Nonetheless, we are getting really close.

In 2021, there were six global cases of wild polio reported in just three countries. There was one case in Pakistan, one case in Malawi, and four in Afghanistan.

Polio is just been incredibly stubborn to stamp out. For example, the case from Malawi was the first case the country had in 30 years and the first in Africa in five years.

To put this into perspective, there were an estimated 400,000 cases worldwide in 1980.

So far in 2022, there has only been one reported case in Afghanistan.

We are getting to the point with polio where we are now just trying to douse the last few glowing embers from the fire.

Even if, theoretically, this 2022 case were to be the last one, it would still be another 10 years before a final deceleration of eradication would be announced.

Another disease that we are very close to totally eradicating is Guinea Worm.

Guinea worm, as the name would suggest, is a parasitic worm that is transmitted via unclean drinking water. It isn’t a bacteria or a virus, so there is no vaccine or treatment for it like there are with other diseases.

Guinea worm isn’t fatal so much as it is painful and debilitating. However, given how it is spread, it also made for a good target for eradication.

The worm is only spread from human to human, almost always from larvae in drinking water. The worm will grow in the intestinal tract and will eventually exit the body, usually quite painfully, via limb.

The only treatment is to remove the worm via winding it up around the small stick over the course of days or weeks.

The good part is that prevention is pretty easy. The larvae can be killed by treating drinking water, or they can be kept out of containers via very simple nylon or cloth filters.

Since the 1980s, the number of guinea worm cases has plummeted. There were an estimated 3.5 million cases of guinea worm in Africa and Asia in 1986.

In 2021, there were only 14 reported cases in 4 countries: 7 in Chad, 4 in South Sudan, 2 in Mali, and 1 in Ethiopia.

Angola and Cameroon saw their last cases in 2020.

The good thing is, not only are we close to guinea worm eradication, but it is much easier to control and eliminate than viral diseases. It can, however, come back.

Of the four countries with cases in 2021, three of them had zero cases in previous years. In fact, Mali had a five-year stretch with only a single case.

The biggest global effort right now towards eradication is probably against malaria.

Malaria is a disease that was found on almost every continent 100 years ago. It can induce fever-type symptoms and in severe cases can result in a coma or death.

It is a bacteria that is spread almost exclusively via mosquitoes. Because the transmission mechanism is via a flying insect, rather than water or direct human contact, that has made it a much more challenging disease to conquer.

The goal of eradicating global malaria was set back in 1955 when the World Health Organization announced the Global Malaria Eradication Program.

There have been great strides in battling malaria, however, we are nowhere near as close to eradicating it as we are with the other diseases I’ve mentioned.

So far, malaria is been completely eradicated in Europe, North America, Australia, the Caribbean, and North Africa.

It has mostly been eradicated in Southern Africa, South America, and most of Asia.

So, that is pretty good progress.

On the other hand, there is still a whole lot of malaria. In 2018 there were estimated to have been 228 million cases of malaria worldwide with an estimated 405,000 deaths. This sounds horrible, and it is but has shown a steady downward trend almost every year.

93% of those cases were in sub-Saharan Africa, with most of the remaining 7% in India and a small number of cases were in the Amazon basin.

The war on malaria is fought on many fronts.

The first and most obvious is against the transmission mechanism, the mosquito.

This is done through pesticides, insect repellants, and mosquito netting. Much of the reduction of malaria in developing countries came from draining pools of stagnant water which were breeding grounds for mosquitoes.

There are also medications that can be used prophylactically to prevent getting malaria, and medication that can be used to treat the disease once you get it.

One of the biggest current areas of research is in malaria vaccines. A malaria vaccine has been elusive but in 2021 there was announced a malaria new vaccine that has been shown to be 75% effective.

That might now sound like much, but a 75% reduction in malaria deaths would be huge, and it would be the single biggest step towards eradication.

We might not see malaria eradication in our lifetime, but we very well might see it become a rare disease.

There have been other major steps taken towards the elimination of other diseases even without an explicit call for eradication.

Vaccines for measles, mumps, and rubella have made those diseases very rare.

Likewise, other parasites such as hookworm, ringworm, tapeworm, lice, and bed bugs have become rarer as well just due to the spread of improved hygiene and sanitation.

The idea of the total eradication of diseases was once a fantasy, but thanks to technology, global coordination, and determination, we have made it a reality. Hopefully, in the years ahead, there were be even more diseases and parasites we end forever.