“As the COVID19 outbreak continues to evolve, we are learning more about this new virus every day” - WHO
It is almost as if the current pandemic strain of coronavirus harbours a natural form of stealth technology. It enters a community and circulates silently, widely, for weeks, before manifesting as symptomatic patients.
In early April, the US Centers for Disease Control and Prevention stated that “we now know from recent studies that a significant portion of individuals with coronavirus lack symptoms” – and that those individuals are contagious. It is for this reason that worldwide, we are being encouraged to distance ourselves socially and stay home insofar as possible.
Asymptomatic (the a in asymptomatic is akin to a for absent symptoms) means infection without exhibiting any symptoms of the disease, which in this case are a dry cough, fever and fatigue. The key question is: how many people with the coronavirus are asymptomatic?
A recent study published in the British Medical Journal found that almost 80% of positive individuals have no symptoms. This is in agreement with a study from a village in Tuscany which showed that 50-75% of positive individuals had no symptoms and there constituted “a formidable source” of contagion. The study also noted that “the percentage of people infected, even if asymptomatic, in the population is very high and represents the majority of cases, particularly, but not only, among young people. Isolation of asymptomatics is essential for controlling the spread of the virus and the seriousness of the epidemic.”
This concurs with a recent Icelandic study that showed that around 50% positive individuals in a large-scale testing exercise were asymptomatic. Even more recently, the South China Morning Post, citing classified data, claimed that China had already found more than 43,000 asymptomatic cases through contact tracing.
However, it is also possible that when these studies were done, people who were found to be asymptomatic with coronavirus were actually presymptomatic, that is, they were still early on in the disease course, in the incubation period, and then went on to become symptomatic and such cases have been documented quite widely. Furthermore, some people who claimed they were well and were tested and found to be positive, when questioned once again, mentioned that they actually did have mild symptoms.
However, as stated by Jeffrey Shaman, an infectious diseases expert at Columbia University, this is a debate in semantics: “The bottom line is that there are people out there shedding the virus who don’t know that they’re infected.” Both groups (asymptomatic and presymptomatic) are contagious and not just symptomatic individuals.
Large-scale testing is therefore crucial to find and isolate asymptomatic or presymptomatic cases as vital to the strategy in containing the spread of the disease and avoid infection of elderly and vulnerable groups.
Workers in the UAE wear masks as they line up to receive their meals. Maks help prevent asymptomatic carriers from spreading the virus. Photo: AFPThere are clearly still many unknowns and Jonathan Ball, professor of molecular virology at the University of Nottingham averred that the “prevalence of asymptomatic or mild disease and its role in virus transmission and the potential role of children in driving this pandemic” are the “key matters that need to be resolved” for us to understand how best to bring the pandemic under check.
The virus’ high level of hidden spread, and the fact that it spreads as easily as ordinary influenza but with a longer incubation period, explains why the coronavirus rapidly escalated to a pandemic in a way that the related SARS and MERS viruses did not.
Tellingly, for those who continue to mention lights at ends of tunnels, Michael T. Osterholm, an infectious disease expert at the University of Minnesota remarked “and when’s the last time anyone thought anything about stopping influenza transmission, short of the vaccine?”
Victor Grech is a consultant paediatrician (Cardiology) at Mater Dei Hospital.