Cultures were attempted in a selected convenience sample of patients. A 500 μL aliquot of the liquid collected from the nasopharyngeal swab were passed through 0.22-μm pore sized centrifugal filter and were then inoculated in wells on 96-well culture microplates, of which four wells contained Vero E6 cells (ATCC CRL-1586) in Minimum Essential Medium culture medium with 4% foetal calf serum and 1% glutamine. After centrifugation at 4000 g, microplates were incubated at 37 °C. Plates were observed every day for evidence of a cytopathogenic effect. The presumptive detection of the virus in supernatant was performed using SU5000 SEM (Hitachi) scanning electronic microscope and then confirmed by specific RT-PCR.