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Summary Background In December, 2007, a family cluster of two individuals infected with highly pathogenic avian influenza A (H5N1) virus was identified in Jiangsu Province, China. Field and laboratory investigations were implemented immediately by public-health authorities. Methods Epidemiological, clinical, and virological data were collected and analysed. Respiratory specimens from the patients were tested by reverse transcriptase (RT) PCR and by viral culture for the presence of H5N1 virus. Contacts of 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. Findings 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. The index case's only plausible exposure to H5N1 virus was a poultry market visit 6 days before the onset of illness. The second case had substantial unprotected close exposure to his ill son. 91 contacts with close exposure to one or both cases without adequate protective equipment provided consent for serological investigation. Of these individuals, 78 (86%) received oseltamivir chemoprophylaxis and two had mild illness. Both ill contacts tested negative for H5N1 by RT PCR. All 91 close contacts tested negative for H5N1 antibodies. H5N1 viruses isolated from the two cases were genetically identical except for one non-synonymous nucleotide substitution. Interpretation Limited, non-sustained person-to-person transmission of H5N1 virus probably occurred in this family cluster. Funding Chinese Ministry of Science and Technology; US National Institute of Allergy and Infectious Diseases, National Institutes of Health; China-US Collaborative Program on Emerging and Re-emerging Infectious Diseases.

WPSAR Vol 4, No 2, 2013 | doi: 10.5365/wpsar.2013.4.2.005 www.wpro.who.int/wpsar 1 a Emerging Disease Surveillance and Response, Division of Health Security and Emergencies, World Health Organization Regional Offi ce for the Western Pacifi c, Manila, Philippines. b Emerging Disease Surveillance and Response, World Health Organization China Offi ce, Beijing, China. * Members of the World Health Organization Regional Offi ce for the Western Pacifi c Event Management Team: Nyka Alexander, Jang Hwan Bae, Joy Rivaca Caminade, Erica Dueger, Xavier Dufrenot, Norikazu Isoda, Frank Konings, Chin-Kei Lee, Ailan Li, Michelle McPherson, Satoko Otsu, Karl Schenkel and Huu Thuan Vo. Submitted: 13 April 2013; Published: 20 April 2013 doi: 10.5365/wpsar.2013.4.2.005 Since 31 March 2013, the Government of China has been notifying the World Health Organization (WHO) of human infections with the avian influenza A(H7N9) virus,1 as mandated by the International Health Regulations (2005).2 While human infections with other subgroups of H7 influenza viruses (e.g. H7N2, H7N3 and H7N7) have previously been reported,3 the current event in China is of historical significance as it is the first time that A(H7N9) viruses have been detected among humans and the first time that a low pathogenic avian influenza virus is being associated with human fatalities.4 In this rapidly evolving situation, detailed epidemiologic and clinical data from reported cases are limited—making assessments challenging— however, some key questions have arisen from the available data. Age and sex data, as one of the first and Human infections with avian infl uenza A(H7N9) virus in China: preliminary assessments of the age and sex distribution

Background Pigs are considered to be “mixing vessels” for the emergence of influenza viruses with pandemic potential. 2009 Pandemic Influenza H1N1 further proved this hypothesis, and raised the needs for risk assessment of human cases caused by swine influenza virus. Methods A field investigation was conducted after a case identified with infection of European avian-like swine influenza H1N1 virus. The diagnosis was confirmed by real-time PCR, virus isolation, whole genome sequencing and serological assays. Samples from local pigs and close contacts were tested to identify the source of infection and route of transmission. Results The virus from the index case was similar to viruses circulating in the local pigs. The case's grandfather was asymptomatic with sero-conversion. A total of 42.8% of swine sera were positive for European avian-like swine H1N1. Conclusions This study highlighted the importance of performing surveillance on swine influenza to monitor new virus emergence in humans.

Cross-species transmission of influenza A viruses from swine to human occurs occasionally. In 2011, an influenza A H1N1 virus, A/Jiangsu/ALS1/2011 (JS/ALS1/2011), was isolated from a boy who suffered from severe pneumonia in China. The virus is closely related antigenically and genetically to avian-like swine H1N1 viruses that have recently been circulating in pigs in China and that were initially detected in European pig populations in 1979. The isolation of JS/ALS1/2011 provides additional evidence that swine influenza viruses can occasionally infect humans and emphasizes the importance of reinforcing influenza virus surveillance in both pigs and humans.

WPSAR Vol 4, No 4, 2013 | doi: 10.5365/wpsar.2013.4.4.003 www.wpro.who.int/wpsar 24 a Division of Health Security and Emergencies, World Health Organization Regional Offi ce for the Western Pacifi c, Manila, Philippines. b Emerging Disease Surveillance and Response, World Health Organization China Offi ce, Beijing, Republic of China. Submitted: 14 October 2013; Published: 31 October 2013 doi: 10.5365/wpsar.2013.4.4.003 We thank Dr Viroj Wiwanitkit for his comments on our preliminary assessment of the age and sex distribution of the human cases with avian influenza A(H7N9) virus infection. To clarify, we posed three scenarios which could possibly explain the preponderance of cases among elderly men reported through China’s surveillance system: (1) differential exposure due to gender-associated practices and norms, e.g. more high risk behaviours among elderly men; (2) differential clinical course post-exposure/ infection, e.g. given similar exposures, elderly men having a more severe outcome relative to other agegender groups; and (3) differential health care-seeking/ access behaviour favouring selection of elderly men, e.g., elderly men accessing health care more than other agegender groups.1 There may be more than one of these possibilities in operation, and this initial assessment was intended to pose the question to public health practitioners and researchers and to encourage further study into the causes for the distribution observed for this apparently emerging disease.2 Our statement that it appeared unlikely that elderly men were being overly selected was addressing this third possibility.

BACKGROUND: We investigated the seropositive rates and persistence of antibody against pandemic (H1N1) 2009 virus (pH1N1) in pregnant women and voluntary blood donors after the second wave of the pandemic in Nanjing, China. METHODOLOGY/PRINCIPAL FINDINGS: Serum samples of unvaccinated pregnant women (n = 720) and voluntary blood donors (n = 320) were collected after the second wave of 2009 pandemic in Nanjing. All samples were tested against pH1N1 strain (A/California/7/2009) with hemagglutination inhibition assay. A significant decline in seropositive rates, from above 50% to about 20%, was observed in pregnant women and voluntary blood donors fifteen weeks after the second wave of the pandemic. A quarter of the samples were tested against a seasonal H1N1 strain (A/Brisbane/59/2007). The antibody titers against pH1N1 strain were found to correlate positively with those against seasonal H1N1 strain. The correlation was modest but statistically significant. CONCLUSIONS AND SIGNIFICANCE: The high seropositive rates in both pregnant women and voluntary blood donors suggested that the pH1N1 virus had widely spread in these two populations. Immunity derived from natural infection seemed not to be persistent well.