Risk factors associated with travel to rabies endemic countries.

Increased travel to exotic destinations around the world is escalating the risk that an emerging virus may be imported into the UK. Rabies should be considered in the differential diagnosis of any encephalitic illness presenting in an appropriate epidemiological context. Molecular diagnostic tests that can rapidly discriminate rabies from other suspected infections will influence the use of anti-rabies prophylaxis for potential contacts with the victim. In 2001, the UK had two confirmed human rabies cases, imported from the Philippines and Nigeria, respectively. In case one, hemi-nested reverse transcriptase polymerase chain reaction (hn-RT-PCR) and automated sequencing confirmed the presence of rabies virus (RABV) within both the saliva and skin specimens within 36 h of sample submission. Subsequent phylogenetic analysis using a partial sequence of the nucleoprotein (N-) gene segment demonstrated that the virus was closely related to that of canine variants currently circulating in the Philippines. In the second case, the fluorescent antibody test and reverse transcriptase polymerase chain reaction (RT-PCR) confirmed the diagnosis on post-mortem tissue. Phylogenetic analysis of two genomic segments of this isolate confirmed that it was a classical RABV (genotype 1) of the Africa 2 subgroup. These cases have highlighted the capability of molecular diagnostic tests for the rapid identification and subsequent genotyping of RABV to host and geographical location. In the first instance, rabies diagnosis often rests on clinical and epidemiological grounds. Negative tests, even late in the illness, do not exclude the diagnosis as these tests are never optimal and are entirely dependent on the nature and quality of the sample supplied. For this reason, rapid molecular detection and virus typing will be essential in considering the appropriate medical treatment regimen for a patient. In addition, an early diagnosis may decrease the number of unnecessary contacts with the patient and reduce the requirement for invasive and costly interventions. Rabies should form part of a differential diagnosis for any patient presenting with a history of travel to a rabies endemic country and displaying an undiagnosed encephalopathy.