Is Second-Wave Coronavirus A More Infectious Strain?

A recent paper in the molecular biology journal Cell suggests that yes, since the first Australian outbreak the coronavirus has become more contagious.

Why is coronavirus getting more contagious?

The change boils down to an “evolved” spike protein, which the SARS-CoV-2 virus uses to “break into” human cells. Formerly known as the D614 spike protein, as identified in the first SARS-CoV-2 samples from Wuhan, the new version has a spike protein called G614.

The D-strain – to call it that – arrived directly from Asia into Australia. Asia and Oceania were hit with the D614 version in January and February, and in these regions, the D-version made up just under half of all SARS-CoV-2 infections through March and April.

Contrastingly, by the end of March the G-strain made up the great majority of cases elsewhere (Europe, Africa and the Americas). Victoria’s second wave is understood to have escaped from hotel quarantine from returning travellers from Europe and North America.

Is the new strain of coronavirus more dangerous?

Carriers infected with the G614 version spread more of the virus. The G614 version is also infectious at a lower concentration than the D614 version. Thus, according to the authors of the paper in Cell, “The consistent increase of G614 at regional levels may indicate a fitness advantage.”

Fortunately, the G614 version is not associated with increased disease severity. It is, however, associated with greater viral load in the upper respiratory tract, which accounts for some of its “fitness advantage” in terms of greater contagiousness.

Aside from its capacity to spread more quickly, the G-strain of SARS-CoV-2 also poses a special challenge for immunologists. Initial development of a coronavirus vaccine was based on what is known as the “Wuhan reference sample.” But as the Cell study authors make clear, “Alterations of the reference sequence as the virus propagates in human-to-human transmission could potentially alter the … efficacy of immune-based interventions.”

Moreover, the virus may continue to evolve to outfox our immune system whilstever it is spreading uncontained. It is a chastening thought considering the months-long vaccine development pipeline.