Symptomatic, Asymptomatic, Pre-symptomatic: How Does COVID-19 Spread?

The World Health Organization has warned us for the past few months that there will be asymptomatic individuals who will serve as "silent carriers" of COVID-19. There is preliminary evidence that there are people who will not show any symptoms of COVID-19 and yet may still transmit the virus.

If you're still confused about how coronavirus has rampaged all over the country, here are some important updates that you need to know about symptomatic, asymptomatic, and pre-symptomatic carriers. It is essential to bear in mind that scientists are continuing their research on a virus that is quite unpredictable in the way it spreads.

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Recently, WHO technical lead on emerging diseases and zoonosis unit Dr. Maria Van Kerkhove said earlier this week: "From the data we have, it still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual. It's very rare."

She also made a distinction between the categories of coronavirus carriers:

• Individuals who are asymptomatic or those who never show symptoms

• Individuals who are pre-symptomatic or those who test positive despite not having symptoms and who will then develop them

• Individuals who are symptomatic or those who show atypical symptoms but don't realize they are already infected

However, the very next day, Dr. Van Kerkhove took it all back and clarified that her statements were misunderstood. She pointed out that transmissions rates of asymptomatic individuals are still unspecified, and they don't have the answer yet on how frequently these individuals pass the disease on to others. 

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On the special WHO question-and-answer session, they addressed the misunderstanding and stated that they are not releasing a new or different policy about the coronavirus. Equally important is the fact that the virus is unpredictable, and that is still plenty of things to know about the dynamics of its transmission. 

However, her first comments created some confusion, and some epidemiologists identified the different ways that the term "asymptomatic" has been used.

The briefing mentioned that it is also a terminology, which can be used to refer to individuals who have yet to show symptoms. In this case, they are called pre-symptomatic, this is where the affected individual can transmit the virus, but he or she isn't sick.

What is the percentage of being infected by an individual who shows no symptoms? 

According to a report, it has been estimated by the US Centers for Disease Control and Prevention that about 40 percent of individuals getting infected by the virus show no signs of being ill. 

It was mentioned in Science that in China, there was a case in which four of the five people who got infected by the coronavirus were due to transmissions from individuals who didn't know had them in the first place.

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