Af­ter Texas re­port­ed its sec­ond case of Ebo­la on Sun­day, ex­perts told CN­BC that air­port screen­ing was un­like­ly to pre­vent an­oth­er po­ten­tial vic­tim of the killer dis­ease from en­ter­ing the US.

Last week, the US gov­ern­ment or­dered five air­ports to start screen­ing trav­ellers for Ebo­la, fol­low­ing the first case on Amer­i­can soil–Thomas Er­ic Dun­can, who died last week af­ter ar­riv­ing from Liberia in Sep­tem­ber. Texas Health Pres­by­ter­ian Hos­pi­tal has now an­nounced that a fe­male care­giv­er who treat­ed Dun­can has caught the dis­ease.

By in­sti­gat­ing screen­ing at five air­ports, in­clud­ing New York's John F Kennedy In­ter­na­tion­al Air­port, the US's Cen­tres for Dis­ease Con­trol and Pre­ven­tion (CDC) hopes to eval­u­ate over 94 per cent of trav­ellers ar­riv­ing from Guinea, Liberia and Sier­ra Leone–the coun­tries worst hit by the out­break. Vis­i­tors will have their tem­per­a­ture tak­en, be ob­served for symp­toms of Ebo­la and asked ques­tions to de­ter­mine their risk of the dis­ease.

Net with very wide holes

Epi­demi­ol­o­gists have warned that there is lit­tle ev­i­dence that this screen­ing will pre­vent an­oth­er vic­tim from en­ter­ing the US, or oth­er coun­tries, such as the UK, which have al­so adopt­ed screen­ing.

"Air­port tem­per­a­ture screen­ing is 'a net with very wide holes'," Ran Bal­icer, a pol­i­cy ad­vis­er and in­fec­tious dis­eases ex­pert at Ben-Gu­ri­on Uni­ver­si­ty, Is­rael, told CN­BC. "If your per­ceived aim would be to pre­vent most cas­es of im­port­ed dis­ease, you are like­ly to fail." The epi­demi­ol­o­gist not­ed that the gap be­tween suf­fer­ers con­tract­ing Ebo­la and de­vel­op­ing a fever could be as long as 21 days–mean­ing that the like­li­hood of po­ten­tial pa­tients be­ing de­tect­ed as they dis­em­bark was slim.

"Be­yond the lo­gis­ti­cal dif­fi­cul­ties, there is al­so a se­ri­ous is­sue of false alarms, es­pe­cial­ly in the flu/RSV sea­son (res­pi­ra­to­ry syn­cy­tial virus) when ran­dom fevers may not be in­fre­quent among trav­ellers." Lawrence Gostin, pro­fes­sor of glob­al health law at George­town Law in Wash­ing­ton DC, said screen­ing would iden­ti­fy no more than a few Ebo­la cas­es at best, and agreed as to the risk of false alarms.

"Will it keep Amer­i­ca safer? Prob­a­bly not, but if it worked at most it would pick up a rare case," Gostin told CN­BC. "We are cur­rent­ly en­ter­ing peak flu sea­son. This could di­vert at­ten­tion and re­sources from oth­er ar­eas of im­por­tance such as pub­lic health and hos­pi­tal pre­pared­ness, which broke down in Dal­las (where Ebo­la vic­tim Dun­can ar­rived)," he added. Air­port screen­ing has been used in oth­er epi­demics, such as the 2003 se­vere acute res­pi­ra­to­ry syn­drome (SARS) out­break, which killed over 8,000 peo­ple.

Lessons from SARS?

Chi­na and Hong Kong were at the epi­cen­tre of the epi­dem­ic and the lat­ter adopt­ed in­ten­sive screen­ing to iden­ti­fy po­ten­tial suf­fer­ers. Oth­er coun­tries al­so adopt­ed screen­ing mea­sures, but the suc­cess of these is dis­put­ed. Cana­da, for in­stance, failed to iden­ti­fy any cas­es of SARS through air­port screen­ing, but suf­fered around 400 cas­es. Forty-four of these pa­tients died.

"Past stud­ies (of air­port screen­ing) did not demon­strate this mea­sure to be ef­fec­tive in con­tain­ing trans­mis­sion of emerg­ing in­fec­tious dis­eases like SARS and pan­dem­ic in­fluen­za," said Bal­icer. In­stead, ex­perts said the most ef­fec­tive way to stop Ebo­la spread­ing glob­al­ly was to boost af­fect­ed coun­tries' health in­fra­struc­ture such that the out­break stopped there.

"Trav­el re­duc­tions and bans will on­ly de­lay the case im­por­ta­tion prob­a­bil­i­ties in a mat­ter of a few weeks, maybe a month. But it will not bring it down to ze­ro," Marce­lo Gomes, a re­search as­so­ciate who is one of a team study­ing the epi­dem­ic at North­east­er Uni­ver­si­ty in Boston, told CN­BC.

50 per cent chance of Ebo­la in UK by end-Oc­to­ber

Gomes and his col­leagues said sev­er­al Eu­ro­pean coun­tries could be hit by Ebo­la by the end of the month–in­clud­ing the UK, which is con­duct­ing air­port screens. They think there is a 50 per cent chance of the virus reach­ing the UK by Oc­to­ber 31, as­sum­ing no re­duc­tion in in­ter­na­tion­al flights, and a 65 per cent chance of a case in France. (CN­BC.com)