Common symptoms of COVID-19 include fever, dry cough, fatigue, sputum production, shortness of breath, sore throat, body aches and headache. 81% of the affected people have mild symptoms. 14% have severe illness and 5% have critical illness requiring ICU level of care. Few affected people do not have any symptoms.
It is now a well known fact that people who do not have any symptoms can still be infectious. Infected people who do not have any symptoms are called “asymptomatic carriers”. The spread of infection by asymptomatic carriers is now considered as playing a more significant role than previously thought. Viral load in asymptomatic carriers is found to be similar to people with symptoms. This further raises concerns over asymptomatic spread of COVID-19 in the communities.
A large study published in the Chinese Journal of Epidemiology, analyzed all COVID-19 cases in China until February 11, 2020. There were a total of 72,314 patient records. It included cases that were diagnosed clinically and also suspected cases. Based on this study, 1.2% COVID-19 patients were asymptomatic or did not have any symptoms. Suspected cases included in this study were very high at 22.4%. As some of the suspected patients may have other non-COVID-19 illnesses, asymptomatic rate may be higher than 1.2%.
The number of cases in the United States alone is over 350,000 at the time of writing this article. 1.2% of 350,000 is around 4,200 people who may be asymptomatic carriers. These asymptomatic carriers may be spreading infection to thousands of other healthy people.
At this point, based on existing evidence, it is difficult to estimate number of people being infected by asymptomatic carriers. Nonetheless, based on the above study, it seems to be a more significant number. Asymptomatic spread is definitely playing a major role in this COVID-19 pandemic.
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