As we've discussed often in the past (see Why Airport Screening Can’t Stop MERS, Ebola or Avian Flu), the prolonged incubation period of many viral illnesses makes airport and other border entry screening a long shot for interdicting infected travelers.
The timing has to be perfect (i.e. the patient has to be symptomatic upon entry), and the traveler has to be forthcoming about previous exposure history.
The WHO’s advice in their August 18th, 2014 Statement on travel and transport in relation to Ebola virus disease (EVD) outbreak.
Affected countries are requested to conduct exit screening of all persons at international airports, seaports and major land crossings, for unexplained febrile illness consistent with potential Ebola infection. Any person with an illness consistent with EVD should not be allowed to travel unless the travel is part of an appropriate medical evacuation. There should be no international travel of Ebola contacts or cases, unless the travel is part of an appropriate medical evacuation
And a statement I wrote about a year ago in WHO: IHR Committee Statement On Thermal Screening For MERS-CoV, which said:
Finally, the Committee indicated that there was no solid information to support the use of thermal screening as a means to stop or slow the entry of MERS-CoV infections, and that resources for supporting such screening could be better used to strengthen surveillance, infection control and prevention or other effective public health measures.
Which is not to say that such screening is useless - only that these sorts of procedures are only likely to detect a small subset of those carrying an infectious disease. They may slow the introduction of an infectious disease into a country, but they are unlikely to completely prevent it.
With one MERS case already having transited Hong Kong undetected, and fears that others might pass through their jurisdiction, the Hong Kong Government today has issued the following statement:
June 01, 2015
Visitors from Seoul with respiratory disease symptoms, and those who recently visited medical facilities in the South Korean capital, will be considered suspected carriers of Middle East Respiratory Syndrome.
This was the message from Centre of Health Protection Controller Dr Leung Ting-hung today, saying they will be required to undergo a medical examination upon entering Hong Kong.
He said the move is to ensure patients are identified as soon as possible to prevent further infections.
It will be implemented immediately, due to the rising number of MERS cases in Seoul and the inability of Korean authorities to provide a list of the country's medical facilities affected by the disease.
Dr Leung urged visitors to truthfully report their health condition to health officials so they can receive timely treatment and prevent infection spread.
He said a 32-year-old man was stopped at Hong Kong airport today and was quarantined at Lady MacLehose Holiday Village.
He is a close contact of the Korean man with MERS who travelled from Korea to the Mainland last week via Hong Kong. It brings the total number of people under quarantine to 19, with none of them showing symptoms so far.