Justin Rother, PharmD candidate, BSc.
What is the confusion about?
Recently, a top official from the World Health Organization (WHO) claimed that the spread of COVID-19 is “very rare” for individuals who are asymptomatic. The WHO has now backtracked on that statement and acknowledged that the available data that we have currently indicates that the majority of transmission is from people who have symptoms of the virus, however, the rates of transmission for people who don’t show symptoms is not yet known. While there has been significant uncertainty over the extent of transmission of the virus from asymptomatic people, it is clear that the WHO’s comments caused confusion to a public that is desperate for clear information on the spread of COVID-19.
How is COVID-19 spread?
COVID-19 is spread via liquid droplets, called respiratory droplets that are transmitted when a person talks, coughs, or sneezes. The virus enters the body with infected droplets and adheres to mucous membranes of a person’s mouth, eyes’, or nose. COVID-19 produces high levels of viral particles in the upper respiratory tract including the nose and mouth and as such, it is quite infectious as the virus escapes into the environment in respiratory droplets. According to the Public Health Agency of Canada, symptomatic cases of COVID-19 cause the majority of transmission of the virus. Asymptomatic transmission of COVID-19 also occurs; however, it is unknown if it is a major driver of infection spread.
What is asymptomatic spread and pre-symptomatic spread?
Some people who are infected will never develop any symptoms at all and are thus considered asymptomatic. It is estimated that between 25 % to 45 % of those infected will be asymptomatic. These people despite not having symptoms are considered carriers and can infect others. In contrast, pre-symptomatic spread occurs from people who do not have symptoms yet but will eventually feel sick later. COVID-19 has a long incubation period, 5-6 days on average. This means there is a significant time between when someone gets infected and when they show symptoms. It is interesting to note that it is impossible to differentiate someone who is pre-symptomatic and will develop symptoms later from someone who is asymptomatic as both carriers look and feel normal. This is further compounded by the fact that some people will have very mild symptoms and will be classified as being asymptomatic. Studying the true number of asymptomatic carriers and how likely they are to spread the virus is an extremely difficult task. A large source of confusion occurs with the terms asymptomatic and pre-symptomatic being used interchangeably by the media. Nevertheless, current research shows that people who will develop symptoms are usually very contagious in their pre-symptomatic phase.
What is the verdict and how do I protect myself?
The US Centers for Disease Control (CDC) has estimated that approximately 40 % of coronavirus transmission happens before symptoms occur. While this statistic is more likely to be pre-symptomatic people than asymptomatic individuals spreading the virus, what’s paramount is that infected people with no symptoms are spreading COVID-19 in the community. As such, it is critical to prevent the spread of the virus by physical distancing, wearing a face mask or covering when in public, as well as practicing proper hygiene by washing your hands with soap and water often and coughing or sneezing into the bend of your arm or a tissue.
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