Study Suggests Detecting New SARS-CoV-2 Variants in Inbound Travelers More Effectively Than Community Surveillance

In a recent study on medrex sib*Preprint server, researchers investigated global surveillance for novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants.

study: Global surveillance for new SARS-CoV-2 variantsImage Credit: Andrey_Popov/Shutterstock.com

*Important Notices: medrex sib We publish a non-peer-reviewed, preliminary scientific report and should not be taken as conclusive, to guide clinical practice/health-related actions, or to be treated as established information.

Background

The ongoing pandemic is being fueled by new SARS-CoV-2 variants that can cause illness and death and cause social disruption.

Early implementation of government policies to limit impacts has proven more effective, but can be costly and should only be applied when necessary. Evidence must be gathered over time to determine the appropriate response to a new variant threat.

However, some countries lack the capacity and resources to conduct timely national surveillance, creating gaps in global surveillance. The UK has adopted extensive hospital surveillance, but research suggests that testing arrivals from the UK to detect new subspecies would be more efficient.

About research

In the current study, researchers created simulations to model the emergence and importation of new SARS-CoV-2 variants with varying infection hospitalization rates (IHR) into the UK. This study compared the time it takes to detect variants through hospitalization, arrival in the UK, and the general community.

The epidemic curve that started in an area of ​​60 million people has resulted in a single wave. On day zero, a proband was reported. The distribution of his first two generations of offspring was fixed at 2 to establish an epidemic.

The epidemic was assumed to have spread for 16 weeks before the mean offspring distribution decreased to account for control measures and the decline in susceptible individuals within the population.

Between the 17th and 26th generations, the average distribution decreased by 0.1 for each generation, leading to a reproduction number of 1 at the 26th generation. The mean offspring distribution decreased by 0.01786 from 27 generations.

Daily prevalence was calculated by adding daily simulated cases following the occurrence of the first case. The epidemic curve was limited to 300 days in simulations. A binomial distribution was used to determine the number of arriving travelers who were harboring or infected each day.

The number of travelers per day was fixed at 250 and the probability was based on the infection rate in the affected area on that day. This assumed that infected individuals were as likely to travel as uninfected individuals. A representative sample of travelers in the % range was selected for testing at the border.

We utilized community cohort observation sizes ranging from 20,000 to 200,000 to detect simulated infection cases within community settings. Surveillance Subject He was tested every two weeks. The study ran epidemic simulations for 1,000 destination countries.

Simulations used the binomial distribution to determine the number of daily detections based on daily testing and simulated prevalence. The sensitivity of the test and the proportion of positive tests sequenced were also considered.

result

This study simulated the time required to detect a new imported subspecies by varying the sampling rate of travelers arriving in the UK. Infection rates within the passenger population were assumed to be comparable to epidemic curves over time recorded in the country of origin.

Furthermore, this study found a non-linear correlation between increased sampling rate and decreased days to detection. This relationship was observed from 131 days to detection by sampling his 10% of passenger arrivals.

The most significant reduction in time to detection occurred when the sampling percentage was between 10% and 20%, with a median reduction of 8 days. The time available decreased as the sampling rate increased.

In this study, we simulated detection time by testing 50% of UK hospital presentations. The team assumed that the increase in incidence in England was comparable to the increase in incidence in the country of origin. Simulations were performed for scenarios with variant IHRs of 1.0%, 1.5%, 2.0%, and 2.5%.

Furthermore, the study found that even with an increased IHR, it took hospitals 10 days or more to detect a new variant compared to sampling the proportion of travelers arriving in the UK.

In this study, we simulated the earliest time to detect new imported variants by testing community groups. When the community cohort size increased from her 0.04% to 0.36% of the community population, the time it took him to detect was reduced by 3 weeks.

The earliest time to detect a sample size of existing communities in England, consisting of approximately 140,000 tests conducted every two weeks, was 157 days.

Conclusion

The findings show that sampling only 10% of inbound travelers for surveillance detected the first case of a novel variant of SARS-CoV-2 imported in England 26 days earlier than existing community surveillance. showed what it can do.

A 50% increase in the traveler sampling rate could improve speed for 43 days. According to the IHR, sampling his 10% of inbound travelers would allow him to detect variants 11 to 19 days earlier than hospital surveillance tests.

International cooperation can help provide broad global coverage of surveillance and can inform national approaches to surveillance. This will give governments more time to formulate policy decisions to respond to new variants of SARS-CoV-2.

*Important Notices: medrex sib We publish a non-peer-reviewed, preliminary scientific report and should not be taken as conclusive, to guide clinical practice/health-related actions, or to be treated as established information.