As planet Earth continues to fight a global pandemic of COVID19, the coronavirus SARS-CoV-2; it seems remarkably ironic that after all of the successes of human endeavour, that we are now being held to ransom by something which is millionth of an inch (17 to 300 nanometers) long. (1)
With international country wide lock downs in place, cases rising daily & the death toll sadly following suit; it is unfathomable how much the entire inhabitants of planet Earth have had to change their lives, as human beings fight an invisible, microscopic killer.
We explored last week about the connection between the destruction of biodiversity & the upsurge in zoonotic disease’s leading to epidemics & pandemics. In the space of a week the novel virus COVID 19 has already superseded the SARS epidemic of 2002 & 2004. Wuhan, China which is still being recognised as the epicentre of the COVID19 virus; has announced that they plan to lift some travel restrictions as of the beginning of April, some nearly six months after they first identified the virus in the live market area of Wuhan.
Therefore, why are coronaviruses so adept at causing so much damage & why are they are so easily transmitted between their animal host & an unsuspecting human being?
‘Kristian Andersen, an associate professor of immunology and microbiology at Scripps Research, and his colleagues looked at the genetic template for the spike proteins that protrude from the surface of the virus. The coronavirus uses these spikes to grab the outer walls of its host’s cells and then enter those cells.(2)
The grabber, called the receptor-binding domain, that hooks onto host cells; and the so-called cleavage site that allows the virus to open and enter those cells.(2)
That analysis showed that the “hook” part of the spike had evolved to target a receptor on the outside of human cells called ACE2, which is involved in blood pressure regulation. It is so effective at attaching to human cells that the researchers said the spike proteins were the result of natural selection and not genetic engineering.’ (2)
With research identifying the zoonotic disease links between other coronavirus origins, civets cats in the case of SARS & camels in the case of Middle East respiratory syndrome (MERS), it is now firmly believed that the COVID19, SARS-CoV-2 virus, was originated in a bat, transferred to an exotic such as a pangolin & then on to the first human host.
One hypothesis for the transmission of the virus, points towards the genetic features that make the new coronavirus so effective at infecting human cells (its pathogenic powers) being in place before transferring to humans (2)
The other scenario considers the pathogenic features would have evolved after transference. Some coronaviruses that originated in pangolins have a “hook structure” (that receptor binding domain) similar to that of SARS-CoV-2 (2) once inside a human host, the virus could have evolved to have its other stealth feature — the cleavage site that lets it easily break into human cells. Once it developed that capacity, the researchers said, the coronavirus would be even more capable of spreading between people. (2)
So how does the transference of a virus lead to a pandemic & why is it such a challenge to track & treat a virus once it reaches pandemic status?
As we explored last week, an archived IPCC report identified the upsurge in zoonotic disease, epidemics & pandemics & cited a:
‘resurgence of infectious diseases in the past few decades, including vector-borne diseases, has resulted primarily from demographic and societal factors—for example, population growth, urbanization, changes in land use and agricultural practices, deforestation, international travel, commerce, human and animal movement, microbial adaptation and change, and breakdown in public health infrastructure’ (3)
This break down in our biodiversity & the international global movements of humans & animals, has paved the way for infectious diseases to run riot in the right environment. A virus needing a host to survive, is well matched to a densely populated area such as Wuhan where it can thrive. Being microscopic, it’s transference abilities are incredible & can multiply at an alarming rate.
One way in which epidemiologists can predict the spread of a pandemic, is through the R0, commonly known as the R-naught. R-naught is the reproductive number of a virus & is used to identify how many people can be infected from one human host.
‘The formal definition of a disease’s R0 is the number of cases, on average, an infected person will cause during their infectious period. (4)
The basic reproduction number represents the maximum epidemic potential of a pathogen. It describes what would happen if an infectious person were to enter a fully susceptible community, and therefore is an estimate based on an idealized scenario. (4)
A number of groups have estimated the R0 for this new coronavirus. The Imperial College group has estimated R0 to be somewhere between 1.5 and 3.5. Most modelling simulations that project future cases are using R0s in that range.’ (4)
With the R-naught for COVID 19 still being fathomed, humans are still only able to follow the guidelines of the scientific & medical sector & try as much as we can to break the chain of infection. By breaking the chain, this would give the human race an opportunity to reduce the number of infections & in doing so identify the R-naught. Once this data has been established, tracking & treating the virus could become easier, as the infection chain amongst humans can be extinguished.
Until this time, the social distancing measures & avoidance of all social gatherings, transference from home to home & all of the other factors being adopted globally, are currently our only line of defence against this microscopic menace & with international Governments working tirelessly to find effective drug treatments & a vaccine; we are still some months away from seeing life returning to whatever our future will look like beyond this global pandemic.
Written by Katy-Jane Mason for & on behalf of Dolphin N2.