The report says the value of exit screening at departing airports is low and the impact of entry screening at arriving airports is also minimal.
Among the reports findings:
Overall, screening for EVD (Ebola Virus Disease) among travelers may detect a few contagious EVD cases over time. Given that exit screening is in place in the affected countries and the poor intrinsic performance of the methods available, entry screening for EVD is likely to have an exceedingly low yield and represents a high investment, which may only contribute to a limited extent, to the prevention of importation of the disease.
predictive positive value of the detection of one individual through screening is extremely low, as no EVD was confirmed in the 77 who were detected out of 36 000 travellers screened.
: The use of screening for infectious diseases has not proven to be effective to prevent or delay transmission in past epidemics such as SARS.
. Screening will result in a significant increase in the request for Ebola testing.
best temperature screening scheme will: − miss up to 20% miss travellers concealing their fever − miss two-thirds of infected cases, still incubating and not yet presenting with symptoms
− detect cases of fever related to many different infectious diseases such as malaria or influenza;
it is likely that EVD cases will account for an extremely small proportion of febrile passengers, if any.
Sensitivity: 8099%, meaning that between 1 and 20% of the febrile passengers will not be detected (false negative)
Specificity: 7599%, meaning that between 1 and 25% of non-febrile passengers will be reported as febrile (false positive).
SARS outbreak
In Australia, 1.84 million arriving passengers were checked. Four suspected cases were detected but not confirmed later. Five probable cases and 20 suspected cases were missed [14].
Canada screened 6.5 million people, detected 9 100 febrile travellers and did not identify any cases [15].
Hong Kong screened 35.6 million people and identified two persons with SARS [16].
Singapore screened 0.4 million people without detecting SARS cases [16].
unspecific symptoms like fever into account, the positive predictive value of a positive screening result for a rare disease is very low, particularly when the prevalence of other febrile infectious diseases among travellers is higher than that of Ebola (e.g. influenza, malaria).
Fever is a symptom that can be temporarily concealed by using antipyretic drugs.
When exit screening at the airports in the affected western African countries is performed following the CDC guidelines [22], the likelihood of disease progression during the flight to Europe (minimum 6 hours) and presenting with high fever at border entry is likely to be low.
Even the combined use of entry and exit screening as performed in Canada during SARS screening when 763 082 persons were screened (467 870 inbound and 295 212 outbound) did not prevent infected persons either leaving or entering the country [30].
Conclusions
The use of screening for infectious diseases has not proven to be effective to prevent or delay transmission in past epidemics such as SARS.
Overall, screening for EVD among travellers may detect a few contagious EVD cases over time.
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Infection prevention and control measures for Ebola virus disease
Entry and exit screening measures 12 October 2014
