Preferred respiratory samples for infl uenza testing include nasopharyngeal or nasal swab, throat swab and nasal wash or aspirate, depending on which type of test is used. Samples should be collected within the fi rst 4 days of illness. Routine serological testing for infl uenza requires paired acute and convalescent sera, does not provide results to help with clinical decision-making. Serological testing results for human infl uenza on a single serum specimen is not interpretable and is not recommended. All respiratory specimens should be kept at 4°C for no longer than 72 hours before testing and ideally should be tested within 24 hours of collection. If storage longer than 72 hours is necessary, clinical specimens should be stored at -70°C [16].