One of the great mysteries of coronavirus is how the epidemic has become much more severe in Europe and North America than in the Far East. A disease which appeared to be on the wane in China, South Korea and elsewhere in mid-February suddenly erupted with a vengeance in Europe in March, with death tolls quickly surpassing those in Wuhan. Various explanations have been offered: from the Chinese lying about the extent of cases and deaths to the difficulties of enforcing lockdowns and launching intrusive tracking and tracing strategies in western democracies.
But then have we really been fighting the same disease? A pre-publication paper from a team at the University of Sheffield and the Los Alamos National Laboratory in New Mexico suggests one reason that Europe and North America might have suffered much more than East Asia from Covid-19 is that we have been fighting a mutation of the virus which causes it, SARS-CoV-2. The team have analysedthe ‘spike protein’ in the virus and found 14 different mutations, but one in particular has caused them concern.
Early in the outbreak – and this was true in Europe as well as in Asia – samples of the virus contained a version of the protein known as D614. But a different version, G614, began to emerge in samples from both Europe and China. In Italy and Switzerland, from early on, it was found to be the dominant version. Elsewhere in Europe, too, G614 rapidly displaced D614 – and seems to have a competitive advantage over it. Germany had a small outbreak of D614 followed by a second eruption of cases of G614. In Britain G614 quickly took over from D614. The same happened in North America – although the pattern is different across the country. In New York, samples have been almost entirely G614 whereas in Washington state – which has won praise for its handling of the epidemic – D614 has been more prevalent. The authors have been unable to track the evolution of D614 and G614 in China after 1 March owing to a lack of samples, but in Japan and Taiwan, early samples were all D614, with the G614 becoming more prevalent after 1 March.
The good news is that the G614 version of the virus does not seem to result in a greater risk of hospitalisation – indicating that it doesn’t cause a more serious form of the disease. However, that does leave open the possibility that the G614 version is much more easily transmissible –perhaps explaining why this disease has proved so much harder to contain in some places than others.
Other mutations were found to be of lesser importance, though do show some interesting patterns. One mutation was found only in Iceland – a country which has been praised for its low number of infections and deaths, in spite of not imposing a full lockdown – and another uniquely in Belgium, the country with the highest death rate in the world.
SARS-CoV-19 is considered to be a relatively stable virus with few mutations, which ought to make it a good candidate for vaccine development. The spike protein, however, is the part of the virus on which most vaccine-development is targeted, and so our chances of having a vaccine will depend on how it evolves from here.