In the past 100 years, the average life expectancy of a human has nearly doubled. There many factors that have allowed this to happen, such as improvements in sanitation, better knowledge of nutrition, and general advances in medical technology, but one of the largest factors has undoubtedly been our concerted effort to eradicate some of the most deadliest diseases on Earth. To date there have been eight diseases targeted for eradication; two of those programs have been successful, two are ongoing, and the remaining four have been abandoned. But with greater technology and resources being devoted to eradication efforts every day, we could soon live in a disease-free future.
How to Squash a Bug
The World Health Organization (WHO) was established in 1948 and acts as the United Nation’s arm for the control and prevention of disease around the world. They have worked to unify global efforts at eradication since the 1950’s, where before, many different organizations would focus on a single disease or region. In building programs to eradicate a specific disease, the WHO makes a distinction between the levels of prevalence of that disease; the goal of elimination is to have the number of hosts in a certain region to be zero, or the number of hosts worldwide to be negligible; the goal of eradication is to have zero hosts worldwide, essentially causing the disease to die out on its own because it has no place to replicate.
The problem is that it is next to impossible to know if a disease has been completely erased from nature. This is less of a problem with diseases that are exclusively carried by humans, especially when the symptoms are unmistakable. Modern medical networks allow new cases to be reported even from the most remove of areas, which is why we are 99.9% sure that nobody has smallpox. However, what if someone is a carrier of the disease but has a natural immunity? They would display no symptoms but could possibly cause an outbreak. Or, what if the disease can also be carried by other mammals? It would be impossible to track down and test every rat in the Amazon rain forest.
Fortunately, these problems are largely a moot point: if there are isolated carriers somewhere in the world, the WHO is confident that they would easily be able to respond to an outbreak – especially since they almost wiped the damn thing off the face of the Earth once already.
The Scientific Conundrums
There are several major challenges that stand in the way of eradicating a disease besides the cost and logistics of treating every known host worldwide. First, most major diseases are caused by either bacteria, parasites, or viruses: bacteria are microscopic living organisms with the ability to live and replicate on their own. Parasites are usually much larger than bacteria, which causes normal immune responses to be less effective. Some parasites have even been known to pacify certain parts of the host’s immune system.
Lastly, viruses are basically non-living shells containing DNA that use a living cell’s own mechanisms to replicate. Put another way, imagine that your cell is getting ready to replicate itself; a virus comes along and attaches itself to your cell, injecting its own DNA inside of it. So instead of the cell replicating its own DNA, it replicates the DNA of the virus. Next thing you know, the machinery of your cell is building a ton of viruses according to the DNA of the original virus. Eventually, the cell bursts and a cluster of new viruses are free to repeat the process in other cells.
Because each type of pathogen (disease-causing agent) is different, each one requires a different treatment. Bacteria are mainly treated with antibiotics, which are usually compounds that slow or stop their replication, allowing the immune system to scoop them up. Parasites are commonly treated with benzimidazole drugs that cause a parasite’s method of fuel intake to degenerate. Viruses are treated with antivirals, which attempt to interfere with parts of the viruses’ life cycle, such as when it attaches to a cell or when its DNA is being copied inside the cell.
And therein lies the problem with treating any one of these three types of pathogens. If you remember back to high school biology, natural selection causes the strongest part of a population to survive and pass on their traits to their descendants, essentially creating populations that are better able to survive in their environment as a whole than the last population. In this case, these populations are pathogens, and the ones that survive are the ones that have a natural resistance or immunity to our treatments. This means that every time we treat a disease, it has the potential to evolve into a new strain somewhere down the line. For this reason, antibiotic and antiviral resistance is one of the most pressing concerns for the eradication efforts of the WHO and for the medical community worldwide.
As early as 10,000 BCE, humanity is believed to have suffered from smallpox. This disease was caused by a couple of variations of the variola virus, one of which killed about one-third of those that it infected. Before death occurred, however, a combination of symptoms including fever, nausea, muscular pain, and of course, blisters covering the entire body. Extreme cases could even cause spontaneous bleeding of the skin. Survivors would be left with very visible scars and sometimes even blindness.
Fortunately, the smallpox vaccine was the first ever developed and was publicized around 1796. Vaccines introduce a small amount of a weakened pathogen so that the immune system defends against the (harmless) infection. In the process, special cells in the immune system develop what is known as an adaptive immunity, allowing your body to remember the pathogen and easily fight against it the next time. After extensive vaccination campaigns throughout the 19th century and into the 20th, there was estimated to be 50 million new cases of smallpox each year. By 1975, smallpox had been eliminated almost everywhere but in the Horn of Africa. In October of that year, a two-year old Bangladeshi girl became the last person to be diagnosed with smallpox. The WHO declared it as officially eradicated in 1979.
After eradication, all stocks of smallpox were either destroyed or transferred to the only two WHO laboratories with the highest level of biological containment safety levels: the Centers for Disease Control and Prevention (CDC) in Atlanta, and the State Research Center of Virology and Biology (VECTOR) in Koltsovo, Russia. Some within the WHO has since insisted that both countries destroy their remaining stocks, but both have been resistant – presumably due their desire to possess it for biological weapon or pandemic defense research.
Saving the Cows
Interestingly, the other infectious disease to have been successfully eradicated was neither harmful to humans nor was it targeted by the WHO; it was rinderpest, a disease that affected cattle, buffalo, and other mammals that have served as a source of food for humans. In fact, the word “rinderpest” is German for “cattle plague”.
Originally thought to have originated in Asia, this viral disease was spread through contact and was known to be very contagious. After centuries of trade and colonization, the disease became common in Europe, with outbreaks occurring every few decades. Rinderpest caused relatively mild symptoms but was known to be 100% lethal in populations that had no natural immunity. Most animals would die within one to two weeks of contracting the virus.
After localized efforts to eliminate the disease throughout the 1900’s, a global eradication program was initiated by the World Organization for Animal Health (OIE) in 1994. The last case of rinderpest was diagnosed in Kenya in 2001, and in June 2011, the disease was declared to be eradicated. It is estimated that this effort cost $5 billion, although its economic benefit will easily exceed this in the years to come.
Ongoing and Failed Programs
In addition to the two successful eradication campaigns to date, there are two ongoing programs that could successfully conclude within the next few decades. The first is for the eradication of guinea worm disease, a debilitating but non-lethal parasitic infection caused by the ingestion of small larvae found in water. There is no drug-based treatment for this disease, so prevention efforts have focused on increasing the safety and supply of fresh water. Many organizations, including the WHO, CDC, and the Bill and Melinda Gates Foundation are focusing on this effort.
The second ongoing campaign is for the eradication of polio, a viral disease that can attack the nervous system and cause paralysis. It is widely believed that this was the cause of President Franklin D. Roosevelt’s paralysis from the chest down. A vaccine for polio was developed in the 1950’s, and today, the disease has been eliminated in most parts of the world. In 2012, less than 250 cases of polio were reported worldwide in only five countries; needless to say, there are high hopes that polio will become the next disease to be declared as eradicated.
Despite these successes, there are still four major diseases whose eradication programs have either been abandoned or indefinitely put on hold; hookworm, malaria, yellow fever, and yaws. Some of these diseases have been eliminated in many parts of the world, such as malaria, but political and economic challenges continue to impede progress. The conclusion of either of the two major ongoing campaigns would mean that many more resources could be devoted to their eradication.
A Disease-Free Future
Despite all of the advances that our civilization has made, one thing has proven constant: mother nature always has power over our feet. Our cities may be leveled by earthquakes, drowned by tsunamis, and of course, emptied by disease. Still, we are living in a period where, for the first time in history, we have the technology to undo the destruction of nature. Diseases are not evil; no bacteria, parasite, or virus enters the body of human intending to do harm. It is simply doing what nature – and God – have designed them to do. The fact that we have conquered a disease which has caused misery to so many is a testament to the ability of our species to survive. In our lifetimes, we may live to see a time when humanity no longer needs to fear disease. Indeed, if disease is ever to be the end of our civilization, it will most likely come at the hands of other humans using the worst of nature for the very worst of intentions.