Rapid Flu Tests in Travelers With Fever

Influenza is a frequent cause of fever in returning travelers. Usually diagnosis rests on the clinical picture. Rapid flu tests are becoming increasingly popular, although their sensitivity and specificity are suboptimal. The objective of this study is to evaluate if rapid flu tests influence the medical management of returning travelers with fever, a population at intermediate risk for influenza infections.

Travelers are at risk of acquiring infectious diseases. Previous studies have estimated that about 11% of travelers develop fever during or shortly after their trip abroad. Influenza has been shown to be one of the most important cause of fever amongst travelers. A sero-epidemiological survey showed that 27 of 211 patients (12.8%) with fever during or after a trip abroad developed antibodies against the influenza virus. Another study showed that 13% of travellers, who consulted after return with flu-like symptoms, had PCR or culture-proven influenza. The incidence of influenza in travellers varies according to the seasons, but cases can be seen year round. In tropical countries transmission is year-long and in the southern hemisphere the flu epidemics occur during the summer of the northern hemisphere. In most hospitals no confirmatory test for influenza is routinely done. For special cases a PCR or viral culture can be requested, but the results are only available after 48 hours for the PCR and after several days for the culture. It is suspected that the inability to confirm the diagnosis of flu contributes to the request of a greater number of useless investigations and inappropriate use of anti-infective treatments. Rapid diagnostic tests are easy to use, relatively cheap and they yield a result within a clinically relevant time frame (30 minutes). For the detection of influenza there are a variety of rapid diagnostic tests on the market. The reported sensitivities and specificities are quite variable, but the new generations report median sensitivities of 70 - 75% and median specificities between 90 and 95%. The rapid tests are considered most useful in patient populations with a significant proportion of influenza cases. The WHO encourages to use rapid diagnostic tests for influenza in returning travelers with fever, considering that this patient population is at significant risk of acquiring influenza during their trip. The aim of this study is to evaluate if rapid flu tests influence the medical management of returning travelers with fever

Inclusion Criteria: Adults 18 years or older Returning from abroad within the last 14 days Documented fever of 38oC or above or anamnestic fever + cough or sore throat within the last 4 days before the consultation. Exclusion Criteria: Unwillingness to participate

Berthod D, Genton B, Hatz C, Blum J, de Valliere S. Ability of physicians to diagnose influenza and usefulness of a rapid influenza antigen test in febrile returning travelers: A randomized controlled trial. Travel Med Infect Dis. 2015 Sep-Oct;13(5):394-9. doi: 10.1016/j.tmaid.2015.08.001. Epub 2015 Aug 28.