Study Examines COVID-19 Transmissibility Post-Infection

Overview of the Research

A recent study from the University of Exeter explores the relationship between the transmissibility of COVID-19 and the time elapsed since infection. The findings suggest that the SARS-CoV-2 virus responsible for COVID-19 may remain transmissible for up to 10 days following infection.

Transmission Patterns of COVID-19

Previous research indicates that the majority of COVID-19 transmissions occur during the early stages of infection or even prior to symptom onset. However, some studies have highlighted prolonged transmissibility in severe cases and among individuals with compromised immune systems. This new study provides evidence that challenges this notion.

Methodology of the Study

The researchers analyzed stored samples from 176 individuals who tested positive for COVID-19 via PCR tests in the UK between March 17 and November 29, 2020. Notably, these individuals were not immunocompromised. The focus was on measuring subgenomic RNAs (sgRNA), which are produced by SARS-CoV-2 during viral protein synthesis. Specifically, researchers examined sgRNA derived from the E-gene, which encodes a protein crucial for viral assembly.

Significance of Testing

Unlike traditional PCR tests that indicate recent infection, this study’s testing approach identifies transmissible infections, providing a clearer understanding of potential contagion.

Correlation Between E-gene Presence and Illness Severity

Among the 176 samples, E-gene sequences were detected in the genome, with 72 showing positivity for E-gene sgRNA. The analysis categorized cases as follows: 74 asymptomatic, 36 mild (fever, headache), 22 moderate (shortness of breath), 33 severe (oxygen saturation ≤ 94%), and 11 critical (respiratory failure). The presence of E-gene sequences was positively associated with illness severity, although no significant correlation was found between E-gene derived sgRNA and severity of illness.

Duration of sgRNA Positivity

Some samples tested sgRNA positive for as long as 68 days, with 13% of these cases exhibiting significant viral levels 10 days post-infection. These results suggest that transmissibility may extend beyond standard isolation periods.

Expert Insights

Professor Lorna Harries, who led the study, emphasized that “our results suggest that potentially active virus may sometimes persist beyond a 10-day period, posing a risk for onward transmission.” She noted that the individuals in the study did not exhibit distinctive clinical features, making it challenging to predict who might remain infectious.

Lead author Merlin Davies highlighted the need for an active viral test to determine when individuals can safely return to communal settings. However, he acknowledged that further research involving larger sample sizes is necessary.

References

1. Davies, M. et al. (2021). Persistence of clinically relevant levels of SARS-CoV2 envelope gene subgenomic RNAs in non-immunocompromised individuals. International Journal of Infectious Diseases; 14:31. DOI: 10.1016/j.ijid.2021.12.312.
2. He, X. et al. (2020). Temporal dynamics in viral shedding and transmissibility of COVID-19. Nature Medicine; 26: 672-675. DOI: 10.1038/s41591-020-0869-5.
3. Lauer, L.A. (2020). The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application. Annals of Internal Medicine. DOI: 10.7326/M20-0504.
4. Van Kampen, J.J.A. et al. (2021). Duration and key determinants of infectious virus shedding in hospitalized patients with coronavirus disease-2019 (COVID-19). Nature Communications; 12: 267.
5. Aydillo, T. et al. (2020). Shedding of viable SARS-CoV-2 after immunosuppressive therapy for cancer. New England Journal of Medicine; 383: 2586-2588.
6. Vennells, L. (2022). One in 10 people may still be infectious for COVID after 10 days, new research indicates. EurekAlert! Accessed 13 Jan. 2022. Retrieved from https://www.eurekalert.org/news-releases/939684.

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