New research from the University of Chicago recently showed that during the first wave of the COVID-19 outbreak in New York City, only between one in five, as well as one in seven cases of the infection, were symptomatic.
A SciTechDaily report indicated that the team of investigators discovered that non-symptomatic or asymptomatic cases considerably add to community transmission, making up at least half or 50 percent of the "driving force of SARS-CoV-2 infection."
The study findings came out on February 10 in the Proceedings of the National Academy of Sciences. When the pandemic occurred in the United States, the study noticed that it was quite difficult to approximate what proportion of people infected with SARS-CoV-2 would continue to develop symptoms, partly because of the initial challenges with the capacity of testing.
According to Rahul Subramanian, a PhD epidemiology student at UChicago and the study's first author, minus the testing capacity data, it is very difficult to approximate the difference between cases that were not reported because of lack of testing and COVID-19 cases were usually asymptomatic. The first author added that they wanted to "disentangle those two things."
Because New York City was one of the first cities that have reported the daily numbers of completed tests, they were able to use the said figures to approximate the number of cases of this virus was symptomatic.
Transmission Rates
While the number of present models utilizing epidemiological data to estimate case numbers, as well as transmission rates that are not detected, this is a pioneering peer-reviewed model to integrate data on everyday testing capacity, as well as alterations in testing rates, over time to offer a more exact picture of what percentage of SARS-CoV-2 infections are symptomatic in a large city in the US.
Louis Block Professor of Ecology and Evolution, Mercedes Pascual, from the UChicago said that integrating such data into the model presented that the percentage of individuals who are symptomatic patients of COVID-19 is somewhere between 13 percent and 18 percent.
Pascual, who's also the study's senior author added, regardless of "uncertainty in all parameters, we can tell that" more than half of the community transmission comes from asymptomatic people, as well as those experiencing pre-symptomatic signs.
While the said data analysis does not specify how contagious individuals without symptoms are, neither account for the new COVID-19 strains that are presently spreading in the US.
The model offers added support for the essentiality of following public health standards to lessen community transmission of the virus, especially if individuals are showing symptoms.
Surprising Proportion
According to the study's co-author, Qixin He, a Purdue University assistant professor, asymptomatic people are not transmitting the infection at high rates. They constitute "something like 80 percent of all infections."
This is quite a surprising proportion, including those who are not showing symptoms, the co-author added, strictly follow public health protocols like wearing a mask and social distancing, and that conducting mass testing is made accessible to everyone.
The study authors explained that these outcomes also establish that public health agencies should make their testing procedures, as well as the numbers publicly available to enable these data to be incorporated into the presently available transmission models.
Making this information available, Pascual said, is as essential as reporting the number of COVID-19 cases.
Otherwise, he added, there is a discrepancy between the number and case types reported over time, as well as the underlying transmission dynamics. This data, elaborated Pascual, is crucial for epidemiological forming.
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