Sally Furniss
Well-known member
From the International Conference on Emerging Infectious Diseases 2008 pg 96 http://www.cdc.gov/eid/content/14/3/ICEID2008.pdf
Board 33. Likely Effectiveness of Quarantine for Pandemic Influenza Control at the Borders of Island Countries
N. Wilson1, H. Kelly2, M. Baker1, G. Sertsou1; 1 University of Otago, Wellington, Wellington, NEW ZEALAND, 2 Victorian Infectious Diseases Reference Laboratory, Melbourne, AUSTRALIA.
Background:
Strict maritime quarantine, with facility quarantine on land, appeared to
reduce the effect of the 1918-19 influenza pandemic in some island jurisdictions. Many island nations now include quarantine in their pandemic plans. We explored the theoretical effectiveness of quarantine and whether it could potentially be shortened with appropriate laboratory testing of quarantined travellers.
Methods:
We used a published method to estimate the time to symptom emergence, given infection at the time of departure and 11-hours of air travel time before quarantine. It was also assumed that 9% of cases remained asymptomatic during the infectious period (also based on a recently published estimate). In particular, we assumed that, in the event of another pandemic, it will be possible to test for the virus using nucleic acid assays with a similar performance profile to assays used for routine diagnosis and surveillance of influenza A (ie, a sensitivity of at least 90% and specificity approaching 100%).
Results:
Using these assumptions we estimated the likelihood of an infected traveller still being asymptomatic and infectious after 3 days quarantine was 4.2% and 1.5% after 6 days. Quarantine effectiveness would be enhanced by longer travel times (eg, estimated to average over 37 hours from Asia to Tuvalu). But such effectiveness could be compromised in islands with limited quarantine facilities and the need to use home quarantine. Quarantine times could potentially be truncated by laboratory testing of those in quarantine. For example, if the prevalence of pandemic influenza infection in arriving passengers in the early part of Pandemic Phase 6 were 1%, the negative predictive value (NPV) of a negative nucleic acid test would be 99.9%. This would decline to only 99.5% for a higher prevalence of 5%.
Conclusions:
In theory the use of facility-based quarantine for 6 days by island nations would substantially reduce the risk of the arrival of pandemic influenza.
The use of diagnostic tests, if available through stockpiling in advance or rapid delivery, may permit a reduction in the quarantine period.
Board 33. Likely Effectiveness of Quarantine for Pandemic Influenza Control at the Borders of Island Countries
N. Wilson1, H. Kelly2, M. Baker1, G. Sertsou1; 1 University of Otago, Wellington, Wellington, NEW ZEALAND, 2 Victorian Infectious Diseases Reference Laboratory, Melbourne, AUSTRALIA.
Background:
Strict maritime quarantine, with facility quarantine on land, appeared to
reduce the effect of the 1918-19 influenza pandemic in some island jurisdictions. Many island nations now include quarantine in their pandemic plans. We explored the theoretical effectiveness of quarantine and whether it could potentially be shortened with appropriate laboratory testing of quarantined travellers.
Methods:
We used a published method to estimate the time to symptom emergence, given infection at the time of departure and 11-hours of air travel time before quarantine. It was also assumed that 9% of cases remained asymptomatic during the infectious period (also based on a recently published estimate). In particular, we assumed that, in the event of another pandemic, it will be possible to test for the virus using nucleic acid assays with a similar performance profile to assays used for routine diagnosis and surveillance of influenza A (ie, a sensitivity of at least 90% and specificity approaching 100%).
Results:
Using these assumptions we estimated the likelihood of an infected traveller still being asymptomatic and infectious after 3 days quarantine was 4.2% and 1.5% after 6 days. Quarantine effectiveness would be enhanced by longer travel times (eg, estimated to average over 37 hours from Asia to Tuvalu). But such effectiveness could be compromised in islands with limited quarantine facilities and the need to use home quarantine. Quarantine times could potentially be truncated by laboratory testing of those in quarantine. For example, if the prevalence of pandemic influenza infection in arriving passengers in the early part of Pandemic Phase 6 were 1%, the negative predictive value (NPV) of a negative nucleic acid test would be 99.9%. This would decline to only 99.5% for a higher prevalence of 5%.
Conclusions:
In theory the use of facility-based quarantine for 6 days by island nations would substantially reduce the risk of the arrival of pandemic influenza.
The use of diagnostic tests, if available through stockpiling in advance or rapid delivery, may permit a reduction in the quarantine period.