The Merriam Webster dictionary defines a virus as follows:[1]
any of a
large group of submicroscopic infectious agents that are usually regarded as
nonliving extremely complex molecules, that typically contain a protein coat
surrounding an RNA or DNA core of genetic material but no semipermeable
membrane, that are capable of growth and multiplication only in living cells,
and that cause various important diseases in humans, animals, and plants.
The definition is in itself complex, starting with the
fact there is no consensus as to whether a virus is a living being or not. The
structure of a virus is quite simple: a protein surrounding a core with genetic
material. Full stop. But even that simple configuration is able to cause
important harm to other living beings.
Since January 2020, the whole world is upside down
thanks to one of these viruses, a coronavirus known as COVID-19. In a series of
entries in this blog, I will discuss, quoting Weezer, how “the world has turned
and left me here, just where I was before you appeared”.[2]
The first entry of this blog mainly discusses, from my
position as non-biologist and non-epidemiologist, how virus work and how
COVID-19 jumped from a cave in China to the largest crisis of mankind in a
century.
The meaning of life when you are a virus
Before saying a few words about the origin of the
COVID-19, let’s make an important point about the purpose of a virus. Indeed,
in our collective imagination we all have an image of an outbreak of a deadly
virus that kills mankind in a quick and dramatic process. Looking only at
movies, I can think about “I am legend”, “World War Z”, “Outbreak”, “12
monkeys” and “28 days later” as portraying that apocalyptical scenario. While
that setting is useful to attract us to the cinema, it may not represent what
one can expect from a virus.
Actually, the main purpose of a virus (and also of any
animal, including us) is to reproduce itself, not to kill their host. A virus
does not have brain so it cannot consciously alter its behaviour to ensure it
jumps from one host to the other, perpetuating itself on Earth. But a virus
that kills its host before it is able to jump to another host is dying with the
host. From this point of view, Ebola, while scary, is a very inefficient virus
as its lethality implies that outbreaks are short-lived and prevents widespread
propagation.[3]
On the other hand, COVID-19 (or the flu) have relatively low mortality rates,
so they have many opportunities to propagate to different hosts, becoming
endemic in the case of the flu. Other viruses, like VIH, remain dormant for a
time in the body of the host, who does not know it is infected and therefore
allows for propagation to other hosts. The underlying purpose of this strategy
is to allow for propagation before killing the host.
It is hard to forecast how COVID-19 will evolve, but a
common view across virologists is that it would become endemic on Earth,
similar to flu. The development of vaccines may alter that path (more on
vaccines in a later entry of this blog), but we should clearly remove the view
that the virus will suddenly disappear from the world. Good news is that new
mutations of the virus should be less lethal and more contagious, as that would
be in line with the Darwinian idea of the survival of the fittest. More lethal
mutations would just be too deadly for hosts and would not propagate too far
(keeping fingers crossed, I am not wrong with this).
Up to here, my small discussion on the nature of
viruses. As further reading, I recommend the book “Spillover” by David Quammen
and, for a more entertaining although equally illuminating reading, “The lost
city of the Monkey God”, by Douglas Preston.
Life in a (real) bat cave
Let’s turn now to the origin of COVID-19. I would like
to be able to offer a conclusive answer here, but I am afraid I am far from
knowing the truth and can only present hypothesis and ideas, for which I lack
evidence. Anyway, here we go.
The most accepted theory about the origin of COVID-19
is that it appeared around an animal market in the Chinese city of Wuhan. The
virus seemed to have jumped from bats to humans, probably taking another mammal
as an intermediate host. In our interconnected and globalised world, it just needed
some weeks to reach the five continents.
From here I want to focus on two aspects: (i) bats,
and (ii) China.
About bats, they seem to be quite an apt host for
viruses due to their habit of living in huge groups (of more than hundred
thousand individuals) in dark and dirty caves, where hygienic conditions are,
let’s put it mildly, poor (not talking about Batman’s batcave, of course). Bats
hang from the ceiling of the cave during the day and, well, go to toilet in
that position. So, their “residual” just falls to the floor or on the walls of
the cave or on other bats. Extrapolating that to hundred thousand bats going to
the toilet day after day in a closed space with poor ventilation, it is easy to
imagine how life looks like there: ideal for viruses to develop. There are
indeed creepy videos of snakes living in these caves together with bats and the
layer of accumulated “residuals”, and feeding on them.[4]
A cave full of bats does not seem a place to be for
humans. However, that brings me to the second point I wanted to raise: China.
Indeed, Chinese growth in the last 30 years has been impressive but has also
implied an amazing development of cities, as an important part of the
population has moved from the countryside to cities. That has put a lot of
pressure on the environment and has made remote places, like bat caves, to come
closer to humans. It has been actually the other way round, humans becoming
closer to bat caves, but I guess you understand what I mean.
Besides, a growing demand for meat of wild animals has
appeared and some people has taken that business opportunity and started to
hunt bats. And what better place to hunt bats that their cave, where you can
find them by very large numbers? It became just a question of probabilities
that a bat living in a cave in China could develop a virus, get in contact with
humans and be able to transmit that virus to humans. The probability of this
event to happen is extremely small (it is easier to win the lottery, provided
you participate, of course) but we were buying a lot of tickets for it to occur.
More frequent interactions between bats and humans in caves meant more
possibilities for the transmission of a virus to humans to happen. With no
human-bat interaction, a virus similar to COVID-19 could have appeared (even
more than once) but it simply died in a dark cave somewhere in a remote place.
In this regard, it is also remarkable that the two
latest major influenza pandemics have been originated in China or Hong-Kong (Hong-Kong
flu in 1968 and more recently SARS). In particular, SARS served as a warning to
mankind of our fragility, but seemingly went unnoticed. In a comparison with COVID-19,
SARS was more lethal and less contagious, even if it took it some hours to
travel from Hong Kong to Canada in a commercial flight, creating havoc
thousands of kilometres away from its place of outbreak. Important lesson that
was not learnt, as flight travelling was going on as normal in the first months
of 2020.
There are many theories about the origin of the virus
that claim it did not come from nature. They are quite diverse, but have the
common point of finding a conspiration of dark forces to create an artificial virus
and let them free through the planet. These theories stem mainly from the extreme
coincidence that the COVID-19 appeared in Wuhan, the city where the Chinese State
has a biological laboratory working with influenza virus. To be honest, I also
find it to be an extreme coincidence, but prefer to keep it there. My feeling
is that we will never know the origin of this virus, as the origin of the
Spanish flu remain unclear (despite its reference to Spain, which had nothing
to do with it).
[1] See https://www.merriam-webster.com/dictionary/virus#:~:text=1a%20%3A%20any%20of%20a,multiplication%20only%20in%20living%20cells%2C.
[3] Unfortunately,
we are not short of deadly viruses on Earth. However, Ebola has attracted a lot
of attention, when compared with Marburg or hantavirus, among others.
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