SARS-CoV-2 variants: How a set of key covariates affect viral kinetics?

A prospective observational cohort study.

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Researchers have been studying how different variants of the coronavirus, known as SARS-CoV-2, are spreading in communities. They found that newer variants are spreading faster than older ones. This is because these variants have changes in their genetic makeup, which make them better at evading the body’s immune response or spreading from person to person.

To understand how these variants spread, scientists looked at data from a group of healthy adults who were regularly tested for the virus. They used a special statistical model to analyze the data and figure out how factors like the type of variant and individual characteristics affected the spread of the virus.

By studying these factors, scientists hope to better understand how the virus spreads and how it interacts with the human body. This information can help guide efforts to control the spread of COVID-19 and develop strategies to combat new variants.

Participants in the study provided information about themselves, such as their age, gender, and any other health issues they had. They were regularly tested for COVID-19 and if they tested positive or showed symptoms, they were given more tests to see how the virus was spreading in their bodies.

These participants also had face-to-face visits after infection to collect more samples and record any symptoms they were experiencing. The researchers used this information to understand how long it took for the virus to show up after someone was exposed to it.

Samples collected from the participants were tested in a lab to detect the presence of the virus. The researchers looked at different parts of the virus’s genetic material to see how much of it was present in each sample. They found that there was a strong connection between the results from different parts of the genetic material.

Scientists studied how the amount of virus changed over time in people infected with different variants of the coronavirus. They used data from a large group of healthy adults and a statistical model to understand these changes. They found that infections with the Delta and BA.2 variants tended to have higher amounts of virus than the BA.1 variant.

They also discovered that factors like age and previous exposures to the virus or vaccines affected how much virus someone had and how long it lasted. Older people and those exposed to the virus or vaccines multiple times had lower amounts of virus.

Additionally, they found that the speed at which the virus was shed early on was related to how long it took for symptoms to appear. This research helps us understand how different factors influence the amount of virus in infected individuals and how it spreads.

The research didn’t show that people with asymptomatic infections got rid of the virus faster. Even after being exposed to the virus, their test results still showed high levels of the virus for up to 14 days. This matches what was seen in studies where people were deliberately infected with the virus in a controlled setting.

The number of vaccine doses or whether someone had symptoms didn’t have a big effect on when the virus peaked or how much of it there was. This suggests that whether someone had symptoms or how often they were exposed to the virus didn’t change how likely they were to spread it.

Jointly accounting for both interindividual variation in Ct values and complex host characteristics—such as vaccination status, exposure history, and age— scientists found that age and number of prior exposures strongly influenced peak viral replication. Older individuals and those with at least five prior antigen exposures to vaccination and infection typically had much lower shedding levels.

Moreover, scientists found evidence of a correlation between the speed of early shedding and the duration of the incubation period when comparing different VOCs and age groups.

Scientists noted, “Our findings illustrate the value of linking information on participant characteristics, symptom profile and infecting variant with prospective PCR sampling, and the importance of accounting for increasingly complex population exposure landscapes when analysing the viral kinetics of VOCs.”

Journal Reference:

  1. Russell TW, Townsley H, Abbott S, Hellewell J, Carr EJ, Chapman LAC, et al. (2024) Combined analyses of within-host SARS-CoV-2 viral kinetics and information on past exposures to the virus in a human cohort identifies intrinsic differences of Omicron and Delta variants. PLoS Biol 22(1): e3002463. DOI: 10.1371/journal.pbio.3002463

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