Our results suggest that the excess burden on the healthcare system was high in the post-pandemic period, which would be a major challenge to any well-managed healthcare system. But it could contribute to fewer fatal illnesses. It has been noted that any present-day projection based on the 1918-1920 pandemic merely presents a worst-case scenario which we can avoid with diligence [19, 20] . However, one should note that the situation today, 90 years later, is very different in many aspects. While modern communication systems may facilitate more rapid spread of infections, implementation of interventions (school closures, masks, hand washing, bans on spitting in public, etc.) may reduce the overall transmission of influenza. Moreover, population demographics, health status and prior exposure to influenza are also different. In 1918-1920 life expectancy was shorter, so the population would have been on the average younger with less prior exposure to influenza, and therefore less compounded by past circulation of influenza as mentioned previously. Our results provide a basis to learn from the past to obtain projections of pandemic scenario and the viable hypothetical parameters for assessing healthcare needs specifically for the current post-pandemic preparedness in every country, including antivirals and vaccines needs for speedy, adequate, and equitable distribution. Finally, while this study is retrospective in design, the study methods can be easily modified for a prospective design and incorporated into a part of syndromic surveillance during a future influenza pandemic to monitor and adjust resources accordingly. Multifunctional nanoparticles as simulants for a gravimetric immunoassay Immunoassays are important tools for the rapid detection and identification of pathogens, both clinically and in the research laboratory. An immunoassay with the potential for the detection of influenza was developed and tested using hemagglutinin (HA), a commonly studied glycoprotein found on the surface of influenza virions. Gold nanoparticles were synthesized, which present multiple peptide epitopes, including the HA epitope, in order to increase the gravimetric response achieved with the use of a QCM immunosensor for influenza. Specifically, epitopes associated with HA and FLAG peptides were affixed to gold nanoparticles by a six-mer PEG spacer between the epitope and the terminal cysteine. The PEG spacer was shown to enhance the probability for interaction with antibodies by increasing the distance the epitope extends from the gold surface. These nanoparticles were characterized using thermogravimetric analysis, transmission electron microscopy, matrix-assisted laser desorption/ionization-time of flight, and (1)H nuclear magnetic resonance analysis. Anti-FLAG and anti-HA antibodies were adhered to the surface of a QCM, and the response of each antibody upon exposure to HA, FLAG, and dual functionalized nanoparticles was compared with binding of Au–tiopronin nanoparticles and H5 HA proteins from influenza virus (H5N1). Results demonstrate that the immunoassay was capable of differentiating between nanoparticles presenting orthogonal epitopes in real-time with minimal nonspecific binding. The detection of H5 HA protein demonstrates the logical extension of using these nanoparticle mimics as a safe positive control in the detection of influenza, making this a vital step in improving influenza detection methodology. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00216-010-4419-8) contains supplementary material, which is available to authorized users. Viruses are the smallest form of life on earth with the ability to replicate and spread within living cells [1] . As they pass from cell to cell, they adapt to evade host immunity and spread disease, creating some of the worst pandemics in history [2] . Improving diagnostics for viruses, such as influenza, would help slow the spread of infection in the event of an emerging virus. It is known that even with reassortment, a common viral defense mechanism, the majority of anti-hemagglutinin (anti-HA) antibodies recognize a specific nine amino acid sequence within the epitope, AYDPVDYPY, which has been the focus of many assays to improve the detection of influenza [3] . Using this immunodominant sequence for the HA epitope, the influenza epitope can be mimicked with a functionalized nanoparticle yielding a comparable affinity to the linear peptide [4] . Another virus, Ebola, has also been effectively mimicked with a monolayer-protected cluster (MPC) through functionalization of the MPC with the antigenic determinant of the Ebola glycoprotein [5] . Integrating biology and materials chemistry using biomimicry in this way has allowed materials chemistry the opportunity to improve current diagnostic treatments, techniques, and limits of detection, but further improvements are still yet to be made [6] .