Symptom-Based Isolation Policies: Evidence from a Mathematical Model of Outbreaks of Influenza and COVID-19

Adam Burns; Alexander Gutfraind

Despite the possible promise of this NPI for both COVID-19 and influenza, it is unclear if symptom-based isolation would be truly effective in controlling outbreaks because the CDC-recommended one day policy might not be enough to achieve a meaningful reduction in transmission, and a high rate of asymptomatic infections and partial compliance might weaken the ability to implement the policy. When the attack rate is high, transmission might occur regardless of isolation and the policy might merely create a burden on the isolated individuals and their families, without a tangible public health benefit. If the policy is proven effective, it is not known whether the CDC-recommended one day of symptom-based isolation is sufficient, and if not, how many days would be most beneficial. At the outset of our project, we hypothesized that these policies would have a small beneficial effect on reducing attack rate, delay the peak of the outbreak and reduce the height of its peak. We did not expect these policies to reduce the overall incidence because there would be many other opportunities to become infected. Furthermore, practical barriers may reduce the strictness with which the policies are enforced, which would reduce the policies' effectiveness.