The world's biggest risks

Ebola airport checks: ‘A net with very wide holes’

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 U.S.

Last week, the U.S. government ordered five airports to start screening travelers 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.

David L. Lakey (L), Commissioner of Texas Department of State Health Services, speaks at a media conference at Texas Health Presbyterian Hospital in Dallas, Texas, October 1, 2014.
Mike Stone | Reuters

By instigating screening at five airports, including New York's John F. Kennedy International Airport, the U.S.'s Centers for Disease Control and Prevention (CDC) hopes to evaluate over 94 percent of travelers 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 U.S., or other countries, such as the U.K., which have .

"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 fever may be not infrequent among travelers."

Read MoreEbola epidemic: Which sectors to watch

Is the Western world at risk from Ebola?

Lawrence Gostin, professor of global health law at Georgetown Law in Washington D.C., 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 epicenter 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.

Read MoreEbola weighs as risks to business rise

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.

Red Cross workers carry away a person suspected of dying from Ebola, in the Liberian capital Monrovia, on Oct. 4, 2014.
Pascal Guyot | Getty Images

"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 Northeastern University in Boston, told CNBC.

50% 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 U.K., which is conducting airport screens. They think there is a 50 percent change of the virus reaching the U.K. by October 31, assuming no reduction in international flights, and a 65 percent chance of a case in France.

"Because of air links, every country in the world is at risk," David Heymann, professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine, told CNBC.

"Every country has to be prepared, because it is not clear where people might be traveling."

Read MoreLearn more about the world's worst Ebola epidemic