Border Control for Infectious Respiratory Disease Pandemics: A Modelling Study for H1N1 and Four Strains of SARS-CoV-2

Abstract

Post-pandemic economic recovery relies on border control for safe cross-border movement. Following the COVID-19 pandemic, we investigate whether effective strategies generalize across diseases and variants. For four SARS-CoV-2 variants and influenza A-H1N1, we simulated 21 strategy families of varying test types and frequencies, quantifying expected transmission risk, relative to no control, by strategy family and quarantine length. We also determined minimum quarantine lengths to suppress relative risk below given thresholds. SARS-CoV-2 variants showed similar relative risk across strategy families and quarantine lengths, with at most 2 days' between-variant difference in minimum quarantine lengths. ART-based and PCR-based strategies showed comparable effectiveness, with regular testing strategies requiring at most 9 days. For influenza A-H1N1, ART-based strategies were ineffective. Daily ART testing reduced relative risk only 9% faster than without regular testing. PCR-based strategies were moderately effective, with daily PCR (0-day delay) testing requiring 16 days for the second-most stringent threshold. Viruses with high typical viral loads and low transmission risk given low viral loads, such as SARS-CoV-2, are effectively controlled with moderate-sensitivity tests (ARTs) and modest quarantine periods. Viruses with low typical viral loads and substantial transmission risk at low viral loads, such as influenza A-H1N1, require high-sensitivity tests (PCR) and longer quarantine periods.

Keywords: diagnosis; quarantine; risk; transmission; viral load; virus.

Scheme 1

The three stages of the simulation process.

Figure 1

Typical log viral load curve by days since infection, labelled with parameters: peak viral load, initial viral load, viral load growth rate, viral load decline rate, time from peak to onset of symptoms.

Figure 2

Test sensitivity by log viral load (in RNA copies/mL) for PCR (red solid), antigen for SARS-CoV-2 (orange dashed) and antigen for influenza A-H1N1 (blue dotted).

Figure 3

Viral transmission risk by log viral load (in RNA copies/mL) for SARS-CoV-2 (red solid) and influenza A-H1N1 (orange dashed).

Figure 4

Log viral loads of virus variants by day of infection for (a) prealpha, (b) alpha, (c) delta (unvaccinated), (d) delta (vaccinated), (e) omicron (vaccinated) and (f) influenza A-H1N1. The median, 25th, 75th, 5th and 95th percentiles of log viral loads are presented by day of infection for each virus variant. All log viral loads and their rates of change are reported in log mRNA units/mL.

Figure 5

Mean relative total TR for ART-based strategies by virus variant: (a) prealpha, (b) alpha, (c) delta unvaccinated, (d) delta vaccinated, (e) omicron vaccinated and (f) influenza A-H1N1. Strategies include the following: pretesting, entry testing and exit testing (red with circles); pretesting, entry testing, testing every three days in quarantine and exit testing (orange with triangles); pretesting, entry testing, testing every two days in quarantine and exit testing (light blue with ticks); and pretesting, entry testing, testing every day in quarantine and exit testing (dark blue with crosses).

Figure 6

Mean relative total TR for strategies based on PCR 2D by virus variant: (a) prealpha, (b) alpha, (c) delta unvaccinated, (d) delta vaccinated, (e) omicron vaccinated and (f) influenza A-H1N1. Strategies include: pretesting, entry testing and exit testing (red with circles); pretesting, entry testing, testing every three days in quarantine and exit testing (orange with triangles); pretesting, entry testing, testing every two days in quarantine and exit testing (light blue with ticks); and pretesting, entry testing, testing every day in quarantine and exit testing (dark blue with crosses).

Figure 7

Minimum quarantine length to pass relative TR threshold, by strategy family (S1, S7, S9, S15, S17) and disease variant. P denotes prealpha, A denotes alpha, Du denotes delta (unvaccinated), Dv denotes delta (vaccinated), O denotes omicron (vaccinated) and H1 denotes influenza A-H1N1. When points overlap, the lowest (strictest) threshold is displayed rather than any higher thresholds, which require the same minimum quarantine length. The remaining strategies are presented in Table S2.1.