When the first wave of the Covid-19 receded, people started to make up for the lost time and have been caught in the second wave. People did not know about the nature of Tsunami (2004), that there were repeated waves, and had to learn the hard way. Similarly, people did not know that Covid could mutate and come in a second wave, faster than the first. Could anybody be blamed? Human nature is such that they would not like to be bound and restricted in movement in their endeavor to live and enjoy a glass of whisky or a coconut shell of toddy. This is why there were riots against the close down enforced in Paris recently.
In June 2020 a research team led by Hyeryun Choe at The Scripps Research Institute in Florida, USA, published their results of a study on the strain of SARS-CoV-2 spreading in the US and Europe. They found that the strain was different from the original strain that spread in China and Asia. They dubbed the new virus strain G614 to differentiate it from the one that spread in China, which had been named D614. The mutant variety G614 was found to be more infectious, that is, its ability to infect people was greater compared to the strain D614.
The ability of a Coronavirus to infect humans depends mainly on the ability of its spike protein that protrudes out on the surface of the spherical virus, to bind with the ACE2 receptor which are molecules present on the surface of human cells in several organs, particularly in the lungs. The researchers had found that the D614 virus often broke off during the process of binding with ACE2 receptors, but the G614 variety was less likely to do so. In other words SARS-CoV-2 has mutated to be able to bind with human cells more effectively. This is a natural process for the survival of the virus. This mutant variety is supposed to be ten times more infectious than the original virus. The researchers say their results are consistent with epidemiological data.
What about death rates, are there more deaths due to the mutant virus? Hyeryun Choe says no, the mutation has not made the virus more lethal. How could that be? If the virus could enter more cells due to its greater ability to bind with host cells, more cells would be affected and more damage could be caused. But the findings are that the spike protein, though it could bind more effectively, has nothing to do with the ability to replicate and there may be other factors that limit intra-host replication. Choe also says that the optimal evolutionary strategy for a virus is to be infectious but non-lethal so that its host population doesn’t die out! If this is the case with the Covid-19, the virus may mutate to produce a strain that wouldn’t mind being symbiotic with humans! Let us hope so.
For the first time in Sri Lanka a group of scientists in Sri Jayewardenepura University, led by Prof. Neelika Malawige, has been able to decode a virus genome. They have done a complete sequencing of the SARS-CoV-2 virus that is spreading in Sri Lanka at present, and have found that there are four different strains and all four are from Clade A, which is the clade that has spread in Australia and the US. A clade in virology is a group of similar viruses based on their genetic sequence. This is excellent work because genome sequencing can help trace the origin of infection, and also help in the development of methods of management of the pandemic.
These findings raise some important questions. Obviously, the second wave virus may not have originated from the first wave virus. The first virus was similar to the one in China, and the second is similar to those in the US and Australia. Epidemiological data support these findings. The daily count of Covid cases in the first wave was about 10 – 20, and in contrast the daily count in the present wave is 400 – 500, which seems to agree with the findings of The Scripps Research Institute. This mutant variety must have come from the US, Europe or Australia. People who are coming back from these countries may have brought the virus.
However, the death rate in Sri Lanka due to the new strain doesn’t seem to have increased and reached the levels in the US or Europe where it is about 1.5 – 3%. In Sri Lanka, thank God, it is still about 0.2%. But as more numbers are affected more deaths could be expected, though the death rate has not changed. Therefore Health Authorities will have to enhance their capacity to manage a larger number of Covid patients and also those who need critical care. The government in its effort to strike a balance between the need for mobility restriction and economic recovery may have to pay greater attention to strict isolation of small affected areas, rather than lock-down of larger areas.
-N. A. de S. AMARATUNGA-