Avian influenza has emerged as one of the primary public health concern of the 21st century. Influenza strain H5N1 is capable of incidentally infecting humans and other mammals. Since their reemergence in 2003, highly pathogenic avian influenza A (H5N1) viruses have been transmitted from poultry to humans (by direct or indirect contact with infected birds) in several provinces of Mainland China, which has resulted in 22 cases of human infection and has created repercussions for the Chinese economy. People have been concerned whether a new pandemic will occur in the future. The eradication of pathogenic avian influenza viruses appears to be the most effective way to prevent an influenza pandemic. This paper will examine the features of H5N1, including incidence, infection, immunity, clinical management, prevention and control, and therapy in Mainland China.
Adolescent ; Adult ; Animals ; Birds ; Child ; China/epidemiology ; Disease Outbreaks/prevention & control ; Female ; Humans ; Incidence ; *Influenza A Virus, H5N1 Subtype ; Influenza in Birds/prevention & control ; Influenza, Human/*epidemiology/immunology/therapy ; Male ; Zoonoses/epidemiology/transmission/virology

OBJECTIVETo investigate the epidemiological features, genetic drift in the epitopes of hemagglutinin (HA) of the novel influenza A (H1N1) virus and oseltamivir-resistant variants characterized by H275Y and N295S mutations in children in Shanghai since the outbreak.

METHODBetween June 2009 and May 2012, a prospective surveillance study was carried out in Shanghainese children who attended the outpatient clinic of Children's Hospital of Fudan University for influenza-like illness. One-step real-time fluorescence quantitative RT-PCR was performed to detect seasonal influenza A and influenza B virus and the novel influenza A (H1N1) virus in the respiratory samples. Genetic drift from the vaccine strain in HA epitopes of the novel influenza H1N1 virus and the molecular markers associated with oseltamivir resistance in neuraminidase (NA) were analyzed.

RESULTOut of 3475 enrolled cases, the novel influenza A (H1N1) virus was confirmed virologically in 222 (6.4%) otherwise healthy children with 133 (59.9%) being boys and 89 (40.1%) girls. The median ages of children with the novel influenza A (H1N1) virus infection during the first wave from August 2009 to February 2010 and the second wave from December 2010 to February 2011 were 53.5 months and 32.0 months, respectively (Z = -4.601, P = 0.000); 119 (46.9%) had the close contact with persons suffering from fever or respiratory infection, of whom, 68 (57.1%) contacts were family members and 47 (39.5%) contacts were classmates. During the outbreak in 2009-2010 season, 66 (40.9%) were exposed to primary index cases, school students were the major exposure subjects, accounting for 50.0%. The nucleotide sequences of HA1 gene were highly homologous between the vaccine strain A/California/07/2009 and Shanghai circulating novel influenza A (H1N1) strains and only S83P mutation in epitope E of HA was detected inclusively in the circulating strains. The H275Y and N295S amino acid mutations associated with oseltamivir resistance were not found in the circulating novel influenza (H1N1) strains.

CONCLUSIONTwo major waves of the novel influenza A (H1N1) outbreaks occurred in Shanghainese children during 2009-2011. Institutional children were the major affected individuals during the 2009 pandemic wave. Households and schools were the main sites of transmission among children during influenza pandemic. Influenza vaccination should be enhanced in children and their close family contacts. The novel influenza A (H1N1) virus in Shanghai has not undergone significant genetic changes. Oseltamivir is effective for the treatment of the novel influenza A (H1N1) virus.

Adolescent ; Amino Acid Sequence ; Antiviral Agents ; pharmacology ; Child ; Child, Preschool ; China ; epidemiology ; Drug Resistance, Viral ; Female ; Hemagglutinins, Viral ; genetics ; Humans ; Infant ; Influenza A Virus, H1N1 Subtype ; classification ; genetics ; isolation & purification ; Influenza, Human ; drug therapy ; epidemiology ; pathology ; virology ; Male ; Molecular Epidemiology ; Molecular Sequence Data ; Neuraminidase ; genetics ; Oseltamivir ; pharmacology ; Pandemics ; Viral Vaccines ; genetics ; immunology