The study co-authored by UMass Chan researchers found wide differences in SARS-CoV-2 infection

The study co-authored by UMass Chan researchers found wide differences in SARS-CoV-2 infection

The wide variation in the amount or infection of SARS-CoV-2 between people in the early stages of COVID-19 may explain the phenomenon of “super diffusers,” according to a study by UMass Chan researchers and collaborators from several institutions that was recently published in Nature Microbiology .

Laura Gibson, MD

The research provides in-depth insight into SARS-CoV-2 infection through serial viral tests in several ways: PCR testing, antigen testing, and viral culture to measure viral growth.

Nasal and saliva samples were obtained in late 2020 through early 2021 from 60 people at the University of Illinois at Urbana-Champaign who had no or mild symptoms of COVID-19. Participants either received a new positive PCR result in the previous 24 hours or were exposed to someone with COVID-19 within the previous five days. The study was supported by the Rapid Acceleration to Diagnosis (RADx) initiative of the National Institutes of Health.

The term superdistributor refers to an infected individual who contributes a disproportionately large proportion to the transmission of SARS-CoV-2.

Co-author Laura L. said Dr. Gibson was previously co-chair of the RADx Clinical Studies Core with David D. McManus, MD, and Richard M. Heydak Professor of Medicine Chair and Professor of Medicine.

Based on the study results, COVID-19 appears to be similar to most other infectious diseases in which some people get sick and some people don’t have the same infection, Gibson said. This clinical variability depends on many factors, including differences between pathogens, individual differences in immune responses or even the location of the virus in the oral or nasal cavities.

The current study was performed on individuals with no known immunity to SARS-CoV-2. They had not been infected before, and since the study was conducted before the vaccine was widely available, none of them had received the COVID-19 vaccination.

The researchers measured the dynamics of the SARS-CoV-2 virus in several ways by taking daily samples from participants for up to 14 days.

First, they tested nasal swabs using a sample from one nostril for the PCR test, which detects viral genetic material whether the virus is dead or alive, and from the other nostril for the antigen test, which detects viral proteins. The nasal sampling was also tested by PCR in viral culture, which is a laboratory analysis that detects live and replicated virus and thus can spread to the next person.

Gibson explained, “The unique aspect of this approach was the use of several testing methods on samples obtained on the same day and the repeating of these procedures daily over the full cycle of SARS-CoV-2 infection.”

To analyze data from these samples, the researchers used mathematical models to map the longitudinal dynamics of virus shedding based on data from polymerase chain reaction (PCR) and viral culture assays conducted over the course of the infection. The models described patterns not only of virus expansion and elimination, but also virus elimination, which generally indicates infectious activity as the virus is released from the body.

“Daily sampling provided participants with accurate, accurate data for this modeling,” Gibson said. “We found that individuals differ greatly in terms of viral infection, and that such variance likely depends on human and viral factors and supports the idea of ​​superspreaders.”

The researchers also compared PCR test results in saliva and nose samples and found surprising differences between the two anatomical sites, even though they are connected at the back of the throat. “We found virus in saliva at least one day before nasal sampling in about 85 percent of the participants,” Gibson said.

The paper’s authors did not suggest that the saliva test was better than the nasal test, “but it supports the argument that if you want to detect infected people sooner, it may be better to test saliva — with a PCR test authorized for this use — rather than nasal samples.” But there are a lot of caveats with this approach, and people should only use diagnostic tests with the specific sample type for which they were designed.”

Although the study was conducted when the alpha and prior variants were traded, Gibson said the general conclusions likely still apply to the other variants because the researchers did not see differences in viral dynamics based on the variants evaluated in this study.

Additionally, the study found differences between participants that were not fully explained by virus test results, Gibson said. “The overall result was that people differed in the amount or duration of virus in samples, regardless of how the virus was tested, and not all of this difference was explained by virus measurements. It is likely that human factors – eg SARS-CoV antibody level -2 in the nose – important and measurable as a clinical tool.”

Other researchers at UMass Chan School of Medicine who co-authored the paper with researchers at the University of Illinois at Urbana-Champaign, Johns Hopkins School of Medicine and the National Institute of Biomedical Imaging and Bioengineering are: Alyssa N. Owens, Ph.D., research coordinator; John B. Bruch, MD, MPH, MBA, assistant professor of emergency medicine; Bruce Barton, Ph.D., Professor of Population Sciences and Quantitative Health Sciences; Peter Lazar, Application Database Developer; and Dr. McManus.

Related UMass Chan news stories:
Participants sought a new digital study of COVID-19 tests at home
New research shows the value of home antigen tests in slowing the spread of COVID-19

2022-05-10 10:56:14

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