Welcome to Naturally Speaking’s blog series on COVID-19. This third post is about the virus and the severity of infection. If we don’t answer all your most pressing questions, please feel free to ask them in the Comments section below – we’ll do our best to respond. We’ll also aim to provide any updates as advice and knowledge evolves. Click here to switch to the more complete version of this post (with extra details and links).
Q. Where did the COVID-19 virus come from?
A. It seems likely that the COVID-19 virus originally comes from an animal source, although it is now spreading from person to person. Bats and pangolins (scaly ant-eaters) have both been suggested as possible sources, but the exact origins of this outbreak remain unknown. Genetic, serological and epidemiological data are all consistently pointing to a start of the outbreak in November/December 2019 in China.
Q. Have changes in the COVID-19 virus’ genetic material affected the severity of the disease?
A. Viruses mutate all the time as they divide and replicate, which is normal. However, there is so far no evidence that the virus has changed in a way that affects the severity of the disease or the potential success of treatments or vaccines that are under development. In short, a vaccine should be effective everywhere and there is no reason to believe the virus is evolving rapidly enough to reduce the protection provided by the vaccination.
Severity of infection outcomes
Q. Why do some people respond better or worse to the virus than others?
A. We don’t know yet. Clear risk factors include age, diabetes, respiratory problems/asthma, immunocompromised/HIV and other co-morbidities, which are more often present among the elderly. On average, men also seem to have more serious disease outcomes than women, although the reasons for this are unknown. Only a small proportion of people who develop symptoms will become seriously ill to the point of requiring hospitalization (about 30%), and only 2.4% require critical care.
Q. Is COVID-19 more or less severe than the 2003 SARS coronavirus? How does it compare with the flu virus?
A. COVID-19 seems to be more contagious, but with less severe symptoms than SARS. The case fatality rate for SARS was estimated at around 15%. It is difficult to estimate the overall case fatality rate of COVID-19 because most of the less severe infections go unreported, and strategies for testing vary widely around the world. As testing increases, so too will the number of confirmed cases – including those that are less severe – which will lead to a decrease in the case fatality rate. Keeping in mind these challenges, the World Health Organisation’s (WHO) most recent estimate is that about 3.4% of reported cases have resulted in death. This is much higher than seasonal flu (which kills much fewer than 1% of those infected).
Feature image is original artwork by PhD candidate Chiara Crestani, ©2020.