BackExit screening for Ebola better than entry screening, says ‘Lancet’
A 'Lancet' study has estimated the number of infected passengers who would fly out of Ebola-hit countries if there were no exit screening
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A Lancet study estimating the number of infected passengers who would fly out of Ebola-hit countries if there were no exit screening, has asked for international cooperation to ensure that such checks are effectively implemented.
According to the modelling research, three Ebola-infected travellers are predicted to depart on an international flight every month from any of the three countries in West Africa battling Ebola outbreaks including Guinea, Liberia, or Sierra Leone, if no exit screening were in place.
A team of doctors led by Kamran Khan at St. Michael’s Hospital in Toronto, Canada analysed 2014 worldwide flight schedules and historic flight itineraries of passengers from 2013 to predict expected population movements out of these three countries.
Such exit screening already exists in the three countries, which is in addition to screening of passengers arriving from these countries at international airports.
The research also used Ebola virus surveillance data from the World Health Organization (WHO) to model the expected number of exported Ebola virus infections and determine how useful air travel restrictions and airport departure and arrival screening might be in controlling the spread of the deadly virus.
This analysis, assuming no exit screening, showed that based on current epidemic conditions and international flight restrictions to and from Guinea, Liberia, and Sierra Leone, on average, just under three (2.8) travellers infected with the Ebola virus are projected to travel on an international flight every month.
“The risk of international spread could increase significantly if the outbreak in West Africa persists and grows," says Khan. “Risks to the global community would further increase if Ebola virus were to spread to and within other countries with weak public health systems," he said in a Lancet note on the research, reviewed by Mint.
Over half of the almost 500,000 travellers who flew on commercial flights out of Guinea, Liberia, or Sierra Leone in 2013 had destinations in five countries including Ghana (17.5%), Senegal (14.4%), UK (8.7%), France (7.1%), and Gambia (6.8%). More than 60% of travellers in 2014 are expected to have final destinations in low or lower-middle income countries, the study points out.
“Given that these countries have limited medical and public health resources, they may have difficulty quickly identifying and effectively responding to imported Ebola cases," says Khan.
The findings indicate exit screening is more efficient and less disruptive rather than screening the same people as they arrive in other countries. The report’s authors also point out that with effective exit screening, the additional utility of entry screening is very low given the short flight durations out of affected countries. In comparison, the Ebola virus has a much longer incubation period, which means an infected traveller arriving at an international airport may not be detected as a carrier.
“Exit screening at the three international airports (Conakry, Monrovia, and Freetown) in Guinea, Liberia, and Sierra Leone should allow all travellers at the highest risk of exposure to Ebola to be assessed with greater efficiency compared with entry screening the same passengers as they arrive in cities around the world," the authors suggest.
“However, this will require international support to effectively implement and maintain," they added.
“The best approach to minimise risks to the global community is to control the epidemic at its source," says Khan.
While entry screening may offer a sense of security, this would have at best marginal benefits, and could draw valuable resources away from more effective public health interventions, the study says. Besides, excessive constraints on air travel could have severe economic consequences and lead to disruption in critical supplies of health and humanitarian services.
“Hence, the decision-makers must carefully balance the potential harms that could result from travel restrictions against any reductions in the risk of international spread," the study suggested.
India started screening for the virus at its airports and ports since August, when the first cases of Ebola infection were reported in West Africa. High-risk passengers are examined at all these entry points.
Some 22,150 passengers were screened at Indian air and sea ports till October 15, as disclosed at a high-level meeting of central and state secretaries in New Delhi last week to review the country’s preparedness for Ebola. The government is also preparing 10 new laboratories across the country to collect and store samples from suspected patients before sending them for medical analysis to the National Institute of Virology in Pune and National Centre for Disease Control in Delhi.
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