Humans are at a great risk of becoming extinct or nearly extinct due to man made reasons like a global nuclear war, global warming and pollution, or global flooding. Humans can also become extinct due to natural disasters like a giant asteroid hitting earth, a mega earth quake, a super volcano eruption.
But there is one threat to humanity that humans should always fear. Not because it may be a threat. But because the threat had become reality in the past, not once, not twice, but many times – even almost wiping out humans sometimes. That threat is the birth of a global killer pandemic. This threat has increased more by the emergence of new strains of killer viruses like SARS, Swine Flue, and the recent Coronavirus.
Pandemics or Mass deaths due to the rise of deadly strains of killer microbes like viruses and bacteria is one of the greatest threats to humanity. A global pandemic might as well cause humans to become extinct if not handled efficiently using proper quarantine measures. Or even better, we should reduce the chances for a new killer strain to be born and spread.
If you are here to quickly read about the recent coronavirus and the reason for its origin in China, skip to the last section of this article.
List of past global pandemics
- An unknown microbe killed around one-thirds to two-thirds of the population of the city-state of Athens in 430 BCE.
- The Antonine Plague killed around 5 million people in the Romain Empire in the second century.
- The Bubonic Plague of 6th century wiped out around half of human population.
- The Black Death of Europe in 14th century killed half of Europe.
- 95% of Native American Population is thought to have been wiped out due to a pandemic introduced to the continent by Europeans.
- And not so long ago, in the 20th century, the Spanish Flu killed almost 5% of the then human population in just 2 years between 1918 and 1920.
This is only a small subset of the list of known global pandemics. And there is list of other pandemics caused by Cholera, Malaria, Tuberculosis, Influenza, Leprosy, SARS, HIV, Ebola etc.
And we don’t even know about the global pandemics that might have wiped out huge human populations in the pre-historic era!
Pandemics today are more deadly than past pandemics
A modern pandemic is more deadlier than an ancient pandemic caused by the same virus or bacteria. Why?
In the past it took long time for people to travel from one place to another. Most of the times, due to little people movement outside the infected zone, many pandemics subside over time.
But in this modern era, all it takes is an inter-continental flight travel by one infected person to take the pandemic to a far away continent – which otherwise would have probably never got it.
The ancient pandemics of Europe or Asia listed above never reached the American continent, because nobody went there from Europe or Asia. But today?
A country can shoot down a nuclear missile launched towards it by an enemy country. But no country can stop the arrival of a new virus from another country, unless of course they completely shut down their borders or ensure complete screening and monitoring of every single person crossing into their borders – be it legal traveller or an illegal immigrant.
According to a simulation by Institute for Disease Modeling, a global pandemic like that of 1918 today could kill around 33 million people in just 6 months!
How is a Pandemic Born?
Why do microbes infect people or other animals and birds in the first place? Because most of these microbes require a living cell to multiply. Viruses cannot multiple outside a host cell. So they take over the machinery of host cells to fuel their reproduction.
According to one theory, viruses are thought to have evolved from pieces of DNA or RNA that slipped out of cells of larger organisms. Whatever their origins, being a small piece of genetic material, they can undergo quick mutation, and given the speed with which they replicate – a single virus can try out thousands of new mutations evolving quickly and adapting to changes in its environment.
While complex organisms like humans require generations together to come up with new mutations, good or bad, viruses can do so within few minutes.
Human Immune System – The Ultimate Saviour
Our immune system knows most of the viral infections through viral signatures – and it can detect, isolate and kill most viruses and other microbes that try to attack us every day. Much of this knowledge is based on experience of our body – experience as a species, heredity, mother’s milk, and in modern times also from vaccines.
But what about a new straing of virus that takes our immune system completely by surprise? What if our immune system is unable to decide a proper response because it has seen some so far unknown, and at the same time deadly intruder virus. The virus has all chances of winning the war with our immune system.
Even in such case, the human immune system will try all weapons in hand, increase temperature, make it difficult for virus to survive inside the body, even if it means losing a lot of its own cells, create a large killer army of different type of soldier cells – and usually a strong and healthy human body will survive the attack of a new virus. It is the immune compromised, weak, generally old people that find it difficult to survive an attack.
But at the same time, even when a healthy human body recovers, the virus continues to spread – especially if it is airborne – making its spread even faster. An air-borne pandemic is generally the deadliest of all – because it is very easy for it to spread. Thank God, HIV is not air-borne!
We are surrounded by thousands of strains of microbes like virus, bacteria, fungi, many of them live inside us, many of them also are good to us, they help us in things like digestion, and in keeping away other dangerous microbes.
So, from where does the new virus come? Where did the ones like SARS, Corona Virus all come from?
Birth of a new Virus – How viruses like Coronavirus are born?
Most viruses and bacteria do not kill their host species. Because if all their hosts die, then the virus or bacteria itself will also become extinct with no host to feed on. So the evolutionary advantage lies in infecting hosts without killing all of them.
So why do new viruses kill humans then? Well, this happens when the virus jumps from one species to another. Take for instance, the bacteria that causes tuberculosis. It does not kill the infected cows. But when the same bacteria infects humans – it can be deadly.
The reason is – the immune systems of cows are used to handling tuberculosis bacteria, just like our immune systems can handle viruses causing cold. But when our immune system is confronted with TB bacteria – it is unable to work out an appropriate response.
Zoonotic Virus – The evolution of a killer virus
So killer viruses are born when they make a successful jump from one species to another. Swine Flue came from Pigs, HIV from Chimps, Nipah from Bats, Coronavirus from Snakes and so on. Nipah doesn’t kill its natural hosts, the bats, else Nipah virus itself will not surive once all the bats die. But it does kill humans, humans are not its natural hosts, and the signature of it not being a human virus, (it is a bat virus) – makes it difficult for human system to recognize it.
Such virus which comes to humans from another species is called a Zoonotic virus, and that makes it very deadly – because human immune systems cannot recognize it with the pace and efficiency it recognizes and responds to other human viruses.
How does a new Zoonotic virus emerge? The 1918 pandemic is said to have been caused when a bird infected with a strain of bird virus and a human infected with a straing of human virus – met the same pig. Inside this pig, the bird virus and the human virus met and mutated creating a new strain of virus – the H1N1.
So, it was a bird flu virus that learnt how to infect humans from a human flu virus – but could evade human immune system because of its bird flu origins – and went on to kill 5% of humans population in just 2 years. Please note that the seasonal human flu from which it originated was never that deadly to humans.
China – Why recent virus outbreaks originate here?
China is famous for its wet markets like the ones in Wuhan, Shanghai, Foshan, Lianghua, etc. Unlike other wet markets where animals arrive dead, in these Chinese wet markets live animals are killed and their meat is sold. This is because customers prefer to see the animals they will be eating to make sure they are healthy.
But this also makes these places a deadly laboratory for viruses to experiment their mutation combinations. The mixing of blood of live animals from different species is a deadly biological lab for the virus strains. And then the new strains make their way to humans easily from here.
It is in one of these markets that the deadly SARS virus was born in 2002. A man in Foshan got sick after preparing a meal of Chicken, Cat and Snake. He was the first case of SARS reported in humans.
And it is in one of these wet markets of China (in Wuhan) that the new strain of Coronavirus – named the Novel coronavirus, evolved in December 2019. Note that Coronavirus is not a new virus – it is a well known family of viruses that is known to cause common cold in humans and different strains of the virus also infect other mammals and birds.
The SARS virus is a specific strain of CoronaVirus that is deadly to humans, and the recent Coronavirus is another new strain that has evolved from a mutation. The latest coronavirus is thought to have come to humans from snakes, the Chinese Cobra – probably from some snake that was killed alive in one of these Chinese wet markets.
Not only China
While the Chinese wet markets are a fertile ground for new strains of viruses to emerge, China is not the only place where new viruses emerge from. After all, given proper conditions, a new strain of virus can evolve any where, any time.
The Nipah Virus was first discovered in Australia, later in Malaysia, then it re-emerged much later in Bangladesh and India. HIV and Ebola originated in Africa. MERS or Middle East respiratory syndrome was first identified in Saudi Arabia.
The 2011 movie Contagion accurately depicts the birth and spread of a virus causing a global pandemic. The flashback at the end of the movie realistically depicts how a bat virus infects a pig which then goes on to infect a human – and how the virus spreads from there. Watch it if you haven’t.
Solutions to control a Pandemic like Coronavirus or SARS
Human co-operation, awareness, proper quarantine and treatment of the infected, hygenic conditions and an efficient administration are the most important aspects of containing a pandemic situation.
As prevention is better than cure, it is better to discourage such wet markets where animals are killed live unless and until proper separation and sanitization is ensured.
- Institute for Disease Modeling
- Coronavirus – Transmission from Snake to Human
- Explained – The Next Pandemic