Search our site

Custom Search

Sunday, 21 June 2020

Coronavirus 101

It’s devastating us now. But where did it come from, where is is going, and what is it anyway?

The disease COVID-19, caused by the virus commonly known as coronavirus, was thought to originate from the Huanan Seafood Market in Wuhan, China, where wild animals, including marmots, birds, rabbits, bats and snakes, are traded illegally. However, recent work has demonstrated that the market is only one possible origin of the disease. Potential patient zeroes – the first human to contract coronavirus – have found to have no link to the market.

© TWDK
The source of the infection has not been identified, but many animals are contenders. The human strand is most similar to a strand found in bats (96% identical DNA) and pangolins (88.5-92.4%).

Scientists are sceptical of the theory that it jumped more than once from animals to people, mostly because there is no evidence that repeated contact with animals has led to any further infections.

In the UK, there was no one single patient zero, and over 1,356 strains have been traced. A family tree for the virus suggests ~34% of cases came from Spain, 29% from France, 14% from Italy and <0.1% from China.

Advanced genome sequencing techniques have been used to probe the coronavirus and its cousin diseases[1]. These viruses are common and most diverse in bats and birds[2][3][4], and as such have been tied to their coevolution and divergence in the carboniferous period, 300 million years ago. But wait... one related coronavirus found in non-migratory bats on different continents was aged at just 200-4,400 years using molecular clock dating analyses – how can that be?

Public Domain via Alexas_Fotos (Pixabay)
Researchers think evolutionary models have used too strong a “purifying” selection, assuming the virus had a drive to end up the way it is today[1]. A new method that models varying strength of natural selection over time was tried out in coronaviruses, and dates them to at least tens of millions of years ago when their natural hosts (bats and birds) started diversifying[2][3][4]. This would give the coronavirus a history similar to that of filoviruses like Ebola[5][6], or herpesviruses[7][8], amongst others.

These finding have important implications for the fight against coronavirus, as it’s possible that if bats and birds coevolved alongside coronaviruses, they developed metabolic and immunological tolerances that we might identify and use to support disease treatment and eradication!

References
why don't all references have links?

[1] Wertheim, Joel O., et al. A case for the ancient origin of coronaviruses. Journal of Virology 87.12 (2013): 7039-7045. doi: 10.1128/JVI.03273-12
[2] Woo, Patrick CY, et al. Discovery of seven novel Mammalian and avian coronaviruses in the genus deltacoronavirus supports bat coronaviruses as the gene source of alphacoronavirus and betacoronavirus and avian coronaviruses as the gene source of gammacoronavirus and deltacoronavirus. Journal of virology 86.7 (2012): 3995-4008. doi:10.1128/JVI.06540-11
[3] Chu, Daniel KW, et al. Avian coronavirus in wild aquatic birds. Journal of virology 85.23 (2011): 12815-12820. doi:10.1128/JVI.05838-11
[4] Vijaykrishna, D., et al. Evolutionary insights into the ecology of coronaviruses. Journal of virology 81.8 (2007): 4012-4020. doi:10.1128/JVI.02605-06
[5] Belyi, Vladimir A., Arnold J. Levine, and Anna Marie Skalka. Unexpected inheritance: multiple integrations of ancient bornavirus and ebolavirus/marburgvirus sequences in vertebrate genomes. PLoS pathogens 6.7 (2010). doi: 10.1371/journal.ppat.1001030
[6] Taylor, Derek J., Robert W. Leach, and Jeremy Bruenn. Filoviruses are ancient and integrated into mammalian genomes. BMC evolutionary biology 10.1 (2010): 193. doi: 10.1186/1471-2148-10-193
[7] McGeoch, Duncan J., and Simon Cook. Molecular phylogeny of the alphaherpesvirinae subfamily and a proposed evolutionary timescale. Journal of molecular biology 238.1 (1994): 9-22. doi: 10.1006/jmbi.1994.1264
[8] McGeoch, Duncan J., et al. Molecular phylogeny and evolutionary timescale for the family of mammalian herpesviruses. Journal of molecular biology 247.3 (1995): 443-458. doi: 10.1006/jmbi.1995.0152
[9] Wang, Lin-Fa, Peter J. Walker, and Leo LM Poon. Mass extinctions, biodiversity and mitochondrial function: are bats ‘special’as reservoirs for emerging viruses? Current opinion in virology 1.6 (2011): 649-657. doi: 10.1016/j.coviro.2011.10.013
[10] Zhang, Guojie, et al. Comparative analysis of bat genomes provides insight into the evolution of flight and immunity. Science 339.6118 (2013): 456-460. doi: 10.1126/science.1230835

No comments:

Post a comment