Probable limited person-to-person transmission of highly pathogenic avian influenza A (H5N1) virus in China.

Two individuals infected with highly pathogenic avian influenza A (H5N1) virus were identified in Jiangsu Province, China. Field and laboratory investigations were immediately implemented. Epidemiological, clinical, and virological data were collected and analysed. Respiratory specimens were tested by reverse transcriptase (RT) PCR and by viral culture for the presence of H5N1 virus. Contacts of the cases were monitored for symptoms of illness for 10 days. Any contacts who became ill had respiratory specimens collected for H5N1 testing by RT PCR. Sera were obtained from contacts for H5N1 serological testing by microneutralisation and horse red-blood-cell haemagglutinin inhibition assays. The 24-year-old index case died, and the second case, his 52-year-old father, survived after receiving early antiviral treatment and post-vaccination plasma from a participant in an H5N1 vaccine trial. Ninety-one contacts with close exposure to one or both cases, without adequate protective equipment, provided consent for serological investigation. The investigations demonstrated that limited, non-sustained person-to-person transmission of H5N1 virus probably occurred in this family cluster. The Lancet. 2008;371:1427-34.