1 Department of Clinical Virology, School of Medicine, University of Crete, Heraklion 71003, Greece.
2 Division of Asthma, Allergy and Lung Biology, King's College London, London SE5 9RS, UK.
3 1st Department of Paediatrics, 'Aghia Sophia' Children's Hospital, Athens Medical School, National and Kapodistrian University of Athens, Athens 115 27, Greece.