RT Journal Article SR Electronic(1) A1 Nava, G M A1 Attene-Ramos, M S A1 Ang, J K A1 Escorcia, M YR 2009 T1 Origins of the new influenza A(H1N1) virus: time to take action JF Eurosurveillance VO 14 IS 22 SP 19228 OP DO https://doi.org/10.2807/ese.14.22.19228-en UL https://www.eurosurveillance.org/content/10.2807/ese.14.22.19228-en