All viruses accumulate mutations over time and the virus that causes COVID-19 is no different. How widespread different strains of a virus become depends on natural selection – the versions that can propagate quickest and replicate effectively in the body will be the most “successful”. This doesn’t necessarily mean most dangerous for people though, as viruses that kill people rapidly or make them so sick that they are incapacitated may be less likely to be transmitted.

Genetic analysis by Chinese scientists of 103 samples of the virus, taken from patients in Wuhan and other cities, suggests that early on two (2) main strains emerged, designated L and S. Although the L strain appeared to be more prevalent than the S strain (about 70% of the samples belonged to the L strain), the S branch of the virus was found to be the ancestral version.

The team behind this research suggested that this may indicate the L strain is more “aggressive”, either transmitting more easily or replicating faster inside the body. However, this theory is speculative at this stage – there haven’t yet been direct comparisons to see whether people who catch one version of the virus are more likely to pass it on or suffer more severe symptoms.*

Dr. Bruce Aylward**, a World Health Organization (WHO) expert, who led an international mission to China to learn about the virus and the country’s response, said that current estimates of a roughly 1% fatality rate are accurate. This would make Covid-19 about 10 times more deadly than seasonal flu, which is estimated to kill between 290,000 and 650,000 people a year globally.

Most people who are not elderly and do not have underlying health conditions will not become critically ill from Covid-19. But the illness still has a higher chance of leading to serious respiratory symptoms than seasonal flu and there are other at-risk groups – health workers, for instance, are more vulnerable because they are likely to have higher exposure to the virus. The actions that young, healthy people take, including reporting symptoms and following quarantine instructions, will have an important role in protecting the most vulnerable in society and in shaping the overall trajectory of the outbreak.

For flu, some hospital guidelines define exposure as being within six feet of an infected person who sneezes or coughs for 10 minutes or longer. However, it is possible to be infected with shorter interactions or even by picking the virus up from contaminated surfaces, although this is thought to be a less common route of transmission.

Scientists were quick out of the gates in beginning development of a vaccine for the new coronavirus, helped by the early release of the genetic sequence by Chinese researchers. The development of a viable vaccine continues apace, with several teams now testing candidates in animal experiments. However, the incremental trials required before a commercial vaccine could be rolled out are still a lengthy undertaking – and an essential one to ensure that even rare side-effects are spotted. A commercially available vaccine within a year would be quick.’

* Hannah Devlin is the Guardian’s science correspondent, having previously been science editor of the Times. She has a PhD in biomedical imaging from the University of Oxford.
** Dr Aylward is the Senior Advisor on Organizational Change to the Director-General. In this capacity he has led the design and implementation of WHO’s Transformation Agenda since September 2017.
In February 2020 Dr Aylward was requested by the Director-General to lead the WHO-China Joint Mission on Coronavirus Disease 2019 (COVID-19).
From August 2016 through August 2017, Dr Aylward worked with the United Nations Office for the Coordination of Humanitarian Affairs (OCHA), initially leading the inter-agency process that resulted in the first-ever system-wide activation procedures for major infectious disease emergencies, then establishing and leading OCHA’s Change Management Unit. In that role he took forward a wide-ranging functional review of OCHA to optimize its role, functions, structure and processes for the challenges of the 21st century.

From December 2015 through July 2016, Dr Aylward led the design and implementation of far-reaching reforms of WHO’s work in emergencies, culminating in the launch of a new WHO Health Emergencies Program. During this period he also led WHO’s response to a wide range of humanitarian and infectious disease emergencies, including the global response to Zika virus.

From September 2014 through July 2016 Dr Aylward served as Special Representative of the Director-General for the Ebola Response, directing WHO’s 2000+ person response to the West Africa outbreak and providing strategic and technical leadership to the United Nations Emergency Ebola Response (UNMEER). Between the early 1990s and 2014, Dr Aylward served WHO in a variety of leadership positions in the areas of emergencies, disease eradication and vaccines and immunization.