• 1
    World Health Organization. Influenza A(H1N1)– update 51. Available at:
  • 2
    Hancock K, Veguilla V, Lu X et al. Cross-reactive antibody responses to the 2009 pandemic H1N1 influenza virus. N Engl J Med 2009; 361:19451952.
  • 3
    Ikonen N, Strengell M, Kinnunen L et al. High frequency of cross-reacting antibodies against 2009 pandemic influenza A(H1N1) virus among the elderly in Finland. Euro Surveill 2010; 15:pii= 19478.
  • 4
    Miller E, Hoschler K, Hardelid P, Stanford E, Andrews N, Zambon M. Incidence of 2009 pandemic influenza A H1N1 infection in England: a cross-sectional serological study. Lancet 2010; 375:11001108.
  • 5
    World Health Organization. Seroepidemiological studies of pandemic influenza A (H1N1) 2009 virus. Wkly Epidemiol Rec 2010; 85:229235.
  • 6
    Wu JT, Ma ES, Lee CK et al. The infection attack rate and severity of 2009 pandemic H1N1 influenza in Hong Kong. Clin Infect Dis 2010; 51:11841191.
  • 7
    Bandaranayake D, Huang QS, Bissielo A et al. Risk factors and immunity in a nationally representative population following the 2009 influenza A(H1N1) pandemic. PLoS ONE 2010; 5:e13211.
  • 8
    Zimmer SM, Crevar CJ, Carter DM et al. Seroprevalence following the second wave of Pandemic 2009 H1N1 influenza in Pittsburgh, PA, USA. PLoS ONE 2010; 5:e11601.
  • 9
    Broberg E, Nicoll A, Amato-Gauci A. Seroprevalence to Influenza A(H1N1) 2009 Virus - Where Are We? Clin Vaccine Immunol 2011; 18:12051212.
  • 10
    Chen MI, Lee VJ, Lim WY et al. 2009 influenza A(H1N1) seroconversion rates and risk factors among distinct adult cohorts in Singapore. JAMA 2010; 303:13831391.
  • 11
    Riley S, Kwok KO, Wu KM et al. Epidemiological characteristics of 2009 (H1N1) pandemic influenza based on paired sera from a longitudinal community cohort study. PLoS Med 2011; 8:e1000442.
  • 12
    Chen H, Wang Y, Liu W et al. Serologic survey of pandemic (H1N1) 2009 virus, Guangxi Province, China. Emerg Infect Dis 2009; 15:18491850.
  • 13
    World Health Organization. WHO Global Influenza Surveillance Network. Manual for the laboratory diagnosis and virological surveillance of influenza. 2011; Available at:
  • 14
    Agresti A, Coull BA. Approximate is better than “exact” for interval estimation of binomial proportions. Am Stat 1998; 52:119126.
  • 15
    Nymadawa P, Burmaa A, Darmaa B et al. The first wave of Influenza A (H1N1) 2009 pandemics in Mongolia. Influenza Other Respi Viruses 2011; 5(Suppl 1):163165.
  • 16
    McCallum L, Partridge J. Epidemiological characteristics of the influenza A(H1N1) 2009 pandemic in the Western Pacific Region. Western Pacific Surveillance and Response Journal 2010; 1:511.
  • 17
    Nukiwa N, Alexanderyn B, Kamigaki T et al. Evaluating influenza disease burden during the 2008–2009 and 2009–2010 influenza seasons in Mongolia. Western Pacific Surveillance and Response Journal 2011; 2:1622.
  • 18
    Mendsaikhan S, Gerelt-Od G, Erdeneuren B, et al. . Mongolian Statistical Yearbook 2010. 2011; 307308.
  • 19
    Cauchemez S, Valleron AJ, Boëlle PY, Flahault A, Ferguson NM. Estimating the impact of school closure on influenza transmission from Sentinel data. Nature 2008; 452:750754.
  • 20
    Wallinga J, Teunis P, Kretzschmar M. Using data on social contacts to estimate age-specific transmission parameters for respiratory-spread infectious agents. Am J Epidemiol 2006; 164:936944.
  • 21
    Xu C, Bai T, Iuliano AD et al. The seroprevalence of pandemic influenza H1N1 (2009) virus in China. PLoS ONE 2011; 6:e17919.
  • 22
    Hens N, Ayele GM, Goeyvaerts N et al. Estimating the impact of school closure on social mixing behaviour and the transmission of close contact infections in eight European countries. BMC Infect Dis 2009; 9:187.
  • 23
    Mossong J, Hens N, Jit M et al. Social contacts and mixing patterns relevant to the spread of infectious diseases. PLoS Med 2008; 5:e74.
  • 24
    McVernon J, Laurie K, Nolan T et al. Seroprevalence of 2009 pandemic influenza A(H1N1) virus in Australian blood donors, October - December 2009. Euro Surveill 2010; 15:pii 19678.
  • 25
    Gilbert GL, Cretikos MA, Hueston L, Doukas G, O’Toole B, Dwyer DE. Influenza A (H1N1) 2009 antibodies in residents of New South Wales, Australia, after the first pandemic wave in the 2009 southern hemisphere winter. PLoS ONE 2010; 5:e12562.
  • 26
    Tang JW, Tambyah PA, Wilder-Smith A et al. Cross-reactive antibodies to pandemic (H1N1) 2009 virus, Singapore. Emerg Infect Dis 2010; 16:874876.
  • 27
    Itoh Y, Shinya K, Kiso M et al. In vitro and in vivo characterization of new swine-origin H1N1 influenza viruses. Nature 2009; 460:10211025.
  • 28
    Potter CW, Oxford JS. Determinants of immunity to influenza infection in man. Br Med Bull 1979; 35:6975.
  • 29
    de Jong JC, Palache AM, Beyer WE, Rimmelzwaan GF, Boon AC, Osterhaus AD. Haemagglutination-inhibiting antibody to influenza virus. Dev Biol (Basel) 2003; 115:6373.
  • 30
    Chen MI, Barr IG, Koh GC et al. Serological response in RT-PCR confirmed H1N1-2009 influenza a by hemagglutination inhibition and virus neutralization assays: an observational study. PLoS ONE 2010; 5:e12474.