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)
