Abstract
Pandemic influenza A (H1N1) has raised global concern and as of 4 August 2009, more than 170,000 cases with 1428 deaths have been reported globally to the WHO. In response, many ongoing studies and projects are attempting to describe this pandemic in more detail with respect to virology, epidemiology and clinical management. The Lancet organized an international conference in Beijing, China on 22–23 August 2009, immediately after the International Scientific Symposium on Influenza A (H1N1) Pandemic Response and Preparedness, which was organized by the Ministry of Health, China. The aim of the Lancet conference was to update scientific knowledge about both seasonal and pandemic influenza. This conference also attempted to provide an insight into fundamental public health and operation strategies to mitigate the impact of seasonal and pandemic influenza within the Asia–Pacific region. In this article, the authors have tried to summarize this conference and discuss future prospects of pandemic preparedness and response.
Strategic preparedness in the Asia–Pacific region
Although 34,026 cases with 64 deaths and 15,771 cases with 139 deaths have been reported in the western Pacific and southeast Asian regions, respectively, the total impact of the pandemic influenza A virus (H1N1), especially its severity, remains uncertain. Richard Cocker from the London School of Hygiene and Tropical Medicine (UK) delivered the keynote address on the conference’s second day. He recognized the current pandemic situation and highlighted the significance of pandemic preparedness and response. He also raised various issues about the health system, and its ability to assess risk factors and cultural differences that may affect policy decisions. Finally, he addressed the importance of global solidarity for information sharing.
Thus far, most deaths have been reported from countries with a higher growth income, possibly because the public health infrastructure may recognize more cases and these cases may require more medical treatment. However, as history has shown, developing countries reported more deaths during the 1918 pandemic, partly owing to less access to health facilities and the fact that few public health measures were implemented to mitigate the impact of the pandemic. In this regard, Hitoshi Oshitani from Tohoku University Graduate School of Medicine (Sendai, Japan) emphasized that it is necessary to assess the severity from various standpoints, including population structure. He suggested that population structure may have a more severe impact on developing countries. Moreover, current assessments indicate that pre-existing medical conditions, such as diabetes and asthma, may increase the severity of cases. Although the exact number remains unknown, available data indicate that the prevalence of noncommunicable diseases is increasing in developing countries, which should also be considered for severity assessment.
Recently, many studies using mathematical modeling have been conducted as part of pandemic preparedness. Several studies in various settings have indicated that rapid containment requires early detection of the first cases and highly established operations. Therefore, mitigation strategies become more important, especially in combination with various measures of nonpharmaceutical and pharmaceutical interventions. Recently, several studies have revealed the transmissibility of this pandemic virus in various outbreak settings, where the basic reproductive number ranged from 1.3 to 2.6. This value tends to be higher than that of seasonal influenza.
Ira Longini from the University of Washington (WA, USA) presented the advantage of modeling in pandemic preparedness, in particular, prioritization of the vaccination strategy for current pandemic influenza H1N1. His model indicated that among the US population, a child-oriented vaccination strategy would decrease the attack rate more than a universal vaccination strategy. In addition, a peak interval is more important for mitigating the impact when considering the availability of vaccination for pandemic influenza H1N1; that is, if the epidemic peak occurs earlier, a higher attack rate will be observed as a result of lower immunization. Therefore, it is also important to mitigate the spread of pandemic influenza to delay the peak in planning the vaccine prioritization strategy.
Public health strategy & operation
Among interventions to mitigate the impact of a pandemic, it is important to consider clinical management, particularly in the management of severe cases during a pandemic. Paul Tambyah from the National University of Singapore (Singapore) presented a lecture entitled “Implications for medical care of an influenza pandemic”. His experience with hospitalized cases, including cases treated in intensive care units, indicated that both health utilization attitudes among citizens and available health resources may affect the increase in hospitalization rate, as well as outpatient visit counts. Hence, if comparing those data internationally, it is important to consider this health utilization situation in countries to prepare for an influenza pandemic in hospital settings. To minimize this potential impact, it is necessary to adjust the existing system to account for an upsurge in the demand for services and also to protect healthcare workers against the infections. A vaccine for this pandemic (H1N1) may be available and this will be an effective tool to protect personnel. However, the uptake of seasonal influenza vaccines among clinicians is still low. Thus, some arrangements such as on-site vaccination should be considered during the present pandemic once vaccines are available. In terms of infection control, there exists at present some evidence-based infection controls for influenza and acute respiratory infections, and at the same time, it is especially important to consider the transmission of pandemic influenza H1N1 in clinical settings.
Another topic of consideration are the nonpharmaceutical interventions, including border control, social distancing and personal hygiene. At present, it is becoming more difficult to contain the virus and many countries should shift their strategies toward mitigation. In this regard, Peter Horby from the National Institute of Infectious and Tropical Diseases (Hanoi, Vietnam) discussed nonpharmaceutical public health interventions to counteract pandemic influenza. He summarized the effectiveness of masks together with hand hygiene; several published studies have demonstrated that masks used in households were of no benefit. As for schools, the use of masks and practicing hand hygiene could decrease the impact with regards to peak attack rate, but the effect is totally dependent upon individual scenarios. He pointed out that it is necessary to consider the timing and interval of infection to minimize the impact of the virus, together with incidental effects such as operational tasks and substantial cost. He concluded that the multiple options available for nonpharmaceutical interventions and earlier implementations have a greater impact.
Lessons & findings from seasonal influenza
Studies on seasonal influenza can be of use for a better understanding of influenza virology and epidemiology. Gavin Smith from the University of Hong Kong (Hong Kong, China) introduced the timescale of origin and the early development of the pandemic influenza A (H1N1) virus and also summarized the genetic evolution of seasonal influenza. Phylogenetic analysis of the current circulating influenza A (H3N2) revealed cocirculating multiple lineages in a single site and even in wider geographical areas. He emphasized the importance of monitoring the virus continuously and closely.
Vaccine prioritization as well as the burden of influenza estimation is becoming one of the major issues. Mark Simmerman from the Coordinating Center for Infectious Diseases, CDC (Bangkok, Thailand) showed that the burden of influenza among children due to seasonal influenza is substantial in Thailand. Influenza seasonality, which is a key data source for developing a model for excess mortality assessment, is complicated in tropical countries and must be monitored over longer periods. In this regard, Paul KS Chen from the Chinese University of Hong Kong (Hong Kong, China) explained that seasonal influenza vaccination is currently prioritized for the elderly population in Hong Kong because many influenza-associated deaths have been reported from the aged population. It seems beneficial to vaccinate the elderly population, however it remains unclear as to what degree it is truly effective. Lone Simmonsen from the George Washington University (WA, USA) described the challenges involved in estimating the effectiveness of seasonal influenza vaccination among the elderly and raised the issue of evaluating the effectiveness of a pandemic vaccine.
Discussion
This was a timely, well-organized and informative conference on pandemic preparedness and response. This conference enabled efficient interaction and networking between the participants. The conference addressed a wide range of issues concerning pandemic influenza preparedness and response. Although countries in the Northern Hemisphere are plunging into the influenza epidemic season with pandemic influenza A (H1N1), it is certain that sharing available data and experiences will serve participants to prepare for and respond to the coming wave. It is anticipated that each country should take necessary actions in considering the local situation as well as available resources. At the same time, international support and collaboration is key in mitigating the impact of this pandemic. It is also essential to monitor the evolution of epidemiological and virological characteristics, which are most indispensable in response to the ongoing H1N1 pandemic.
Financial & competing interests disclosure
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.