Studies indicate that we may have vastly underestimated how far the virus has spread
A major reason why there is so much uncertainty surrounding the danger posed by this novel coronavirus is that a large proportion of cases seem to be mild or asymptomatic (no symptoms). This makes it very hard to estimate how many people have actually been infected, and could be leading to gross over-estimates of the ‘true’ death rate. Even for those infected by normal influenza, 5% to 25% are estimated to be asymptomatic.
The New York antibody test, mentioned in ‘Part 2’ of this review, suggested that over one-fifth, 21.2%, of its residents had already had the virus, which is ten times that of official cases.
A recent study, published in the British Medical Journal and based on 3665 people from mainland China, suggested 78% of people with Covid-19 displayed no symptoms. This was similar to the findings in the Italian town in the epicentre of the ourbreak, where 50-75% were asymptomatic, Another Italian study found 43% and an Icelandic study found this number to be 50%.
An earlier report from the Diamond Princess Cruise Ship reported only 17.9% of the cases were asymptomatic and found a fatality rate of 1.1%. However, the large majority, 78%, were over 60 years old, meaning they were far more likely to have worse symptoms and less likely to be asymptomatic. The danger posed by coronavirus to different age demographics will be evaluated in a future installment of this review.
A WHO report found “80% of infections are mild or asymptomatic, 15% are severe infections and 5% are critical infections”. Even though this will be an over-estimate, it points to the fact that the majority of cases will not be severe enough to go to hospital, and therefore will not be tested, or become ‘reported cases’, especially in the inital stages of the outbreak.
The two Italian studies reported that the virus was very contagious and that those without symptoms posed the same threat of contagion than those with symptoms, based on how much of the virus was found in the individuals’ samples. Part of the reason coronavirus seems very contagious is because it is a novel or new virus and no one has built up immunity to it.
It is clear that the novel coronavirus is far more widely spread than currently reported, but just how extensively will only be revealed with time.
What do you think? Read the next installment in the Covid-19 Review here! It compares coronavius to ‘normal’ flu.