Wednesday, 18 March 2015

The effectiveness of border entry screening for infectious diseases, has it been a success?

Dr Robert Hall has co-authored a paper with researchers from Curtin University discussing the systems in place for border-screening of SARS and influenza and possible border strategies for controlling future disease outbreaks.

The SARS pandemic which occurred in 2003 and the outbreak of H1N1 influenza in 2009 propelled countries to implement stronger border screening processes. Border screening processes are intended to prevent future spread of a disease or virus by identifying infected individuals and prohibiting their entry into a country. This is used alongside quarantine, a measure which isolates an individual who may be infectious along with any others they may have had contact with.

The World Health Organization has previously encouraged sick individuals with influenza to postpone all travel during the influenza pandemic. Furthermore, they have suggested use of strong border screening measures for travellers from countries impacted by SARS in 2003 and Ebola in 2014. These measures have been implemented using visual inspection of all travellers, the use of thermal image scanners to determine if an individual has a fever, health declaration cards, and informing local health departments of any ill travellers. The authors sought to examine the effectiveness of these measures by critiquing these border-screening practices.

Border-screening measures have not been fully successful in meeting their major goal; identifying infectious individuals. There are a number of reasons for this. A major obstacle for identifying travellers with influenza is the short incubation period. Thermal imaging is ineffective as not all individuals with influenza have a fever. Statistics from the epidemic of influenza in Singapore showed that 12.9% of cases were identified by airport border screening. In Japan, only 6.6% of individuals were identified at the airport. The authors reviewed a past hospital-based study that explored the effectiveness of thermal imaging scanners in identifying individuals with fever. The ability of thermal scanners to detect fever was both low and inconsistent, between 4% and 89.6%.

The SARS outbreak in 2003 led to the implementation of different preventive measures by several countries to prevent cross-country transmission. These included warnings regarding travel, educational material and border screening. Australia had not used thermal imaging scanning at this time, identified four possible cases at point of entry, none of whom were confirmed as having SARS. Due to the very low prevalence of the infection amongst travellers, the predictive value, i.e. the chance of a traveller actually having SARS after showing a raised temperature at a border screening point is nearly zero.

The authors conclude that the use of these border screening measures have little effectiveness in identifying sick individuals and preventing the importation of disease. The measures require large staff resources and have high opportunity costs. They suggest that the use of communication regarding the outbreaks at the point of entry alongside communication with health professionals may be more effective in controlling the spread of imported infections, especially when combined with disease control systems within communities.

Read the full paper here.

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