A year on, new Covid-19 strain threatens to bring back old chaos

As a few Covid-19 vaccines began rolling out, the world crossed its fingers, looking forward to better times in the coming year, hoping to limp back from the aftermath of the pandemic. However, the tale took an ugly turn in mid-December when scientists in the UK reported a new variant of  SARS-CoV-2  — potentially more contagious than the present one — is on the prowl.

The UK faced a sudden surge in Covid-19 cases in the past week, causing panic and concern. Authorities observed alarmingly that the new viral strain was baring its fangs and rapidly replacing the other variants. The nation hastily implemented stricter lockdown measures to mitigate the spread of the virus.

Mutant alert

Like any other organism, viruses respond to survival threats by undergoing changes and adapting to stress. These evolutionary changes called mutations, occur in their genetic code. As viruses are positioned at the lowermost rung of the evolutionary ladder, they are prone to rapid transformations. Any change that gives the virus a better chance to invade host cells gives it an edge to survive. A classic example is the many variants of the influenza virus that emerge each year.

The SARS-CoV-2 is no different and has undergone several changes. In fact, the viral strain currently circulating worldwide is different from that which emerged in China initially. According to the Science magazine, the virus has been mutating at the rate of one to two changes per month, modifying 20 points on its genetic sequence.

However, the present UK strain has leapfrogged the evolutionary cycle, undergoing as many as 17 genetic changes. The mutant keeps scientists on tenterhooks as two of the variations significantly affect the spike protein, improving its survivability. As is known, the virus uses the spike to hook to host cells and invade it.

The two mutations — technically labelled as N501Y and P681H — dramatically influence the viral transmissibility and its virulence (ability to cause damage to host cells). What stands out is that although these changes have occurred earlier, they happened independently. But, they have now appeared together to help the virus propagate faster and cause damage to the host body.

The cause of worry arises as N501Y influences how tightly the spike locks with ACE2 — the receptor protein in the host cell that provides a gateway for the virus. Another change named H69-V70del has the structural potential to hoodwink the host immune system.

What it entails

The viral strain is labelled as VUI 202012/01 (Variant Under Investigation, year 2020, month 12, variant 01 or B.1.1.7). Preliminary epidemiological reports in the UK show that this virus strain is 40-70% more transmissible than the currently circulating variants.

The World Health Organization reports that the new variant has been traced in Australia, Italy, Ireland, Denmark, and the Netherlands. Also, South Africa noticed a similar strain earlier. Many nations have closed their borders to curb the spread of the virus.

The situation raises several questions.

Firstly, will the diagnostics be affected? PCR assays target particular genes for testing. The H69-V70 del mentioned earlier has shown to affect some PCR diagnostic performances. However, since many PCR tests are assessed on multiple gene targets, overall, there will be no significant impact in diagnostics.

Second, will the emerging vaccines be useful on this viral strain?

To this end, experts opine that it is too early to conclude anything. It calls for in-depth investigations which are time-consuming.  However, some others opine that as many vaccines trigger an immune response targeting multiple areas on the spike protein, the vaccine’s overall effect may still hold.

Meanwhile, global efforts are underway to track and sequence the minutest changes occurring in the viral genes.

Third, does this strain increase disease severity?

UK scientists are rigorously assessing the infection severity, antibody response and other relevant factors. The present data do not indicate, nor are there conclusive reports to show an increase in the disease symptoms or severity. However, extensive epidemiological data will ascertain if there are different disease outcomes.

In all, the virus is presently restricted to a few countries for now. Health authorities around the world continue to be vigilant and caution against slackness of mitigating measures. As one expert told The New York Times, “Evidence is accumulating that the variant is more transmissible, and this implies that it will likely require even greater effort to keep the spread under control.”