Pandemic Flu symposium - reflections on the meeting by Dr McIntyre

Session 162
November 23rd 2006

Some 40 members of the Society met in the Ebenezer Duncan Centre with the President, Mr David Ritchie, in the chair. The main business of the evening was a
symposium on Pandemic Flu addressed by Dr Graeme O’May of the Regional Virus Laboratory, Dr Mark Cotton, Respiratory Physician, Dr Helene Irvine of the Public Health Department and Dr Colin Robertson currently working with the Scottish Office on Pandemic Flu planning.

Dr O’May described the mechanisms of genetic change in the flu virus - genetic drift by gradual mutation over time or shift by a reassortment of gene segment between avian and human viruses. These changes could produce increased pathogenicity or transmissibility. If both occurred a pandemic flu could arise. He emphasised that the current H5N1 avian virus was indeed bad news for birds but not for humans. He went onto explain laboratory identification of influenza and how this might respond to pandemic flu. PCR on throat and nose swabs can produce a result in a matter of hours. Laboratory resources would be focused on influenza with working arrangements changed to allow continuous testing. If there seemed a risk of pandemic flu spreading there would be particular attention to viral testing in children where flu tends to appear first. Finally he addressed the difficult issue of vaccination – if vaccines are prepared too early the strain may be wrong, if too late vaccine would be ineffective. The current H5 vaccine is in fact not sufficiently immunogenic to be effective.

Dr Cotton gave an overview of the clinical features of influenza and highlighted some of the differences between epidemic and pandemic flu with the varying virulence of different strains. The 1918 pandemic seemed particularly virulent with the feature found also in other pandemics of a peak of mortality in young adults – 20 times that of epidemic flu. This is likely to be related to primary influenza pneumonia, a disease of rapid onset and progression. The other major distinction from epidemic flu is timing – pandemic could occur at any time of year and seemed to follow a 3 phase pattern over the course of up to a year. However, the severity of the disease could be locally variable. A 1951 epidemic flu outbreak in Liverpool produced a local death rate greater than that of 1918. Dr Cotton emphasised the broad range of non respiratory illness caused by influenza and in particular increased mortality from coronary artery and other vascular disease. There is therefore a inevitable degree of uncertainty of predicting the clinical features of pandemic flu from what we know about epidemic flu and for example recent human cases of H5N1. At one end of the spectrum there is the acute lung injury of influenza pneumonia – at the other end a variety of clinical presentations in the first few days of illness though with a tendency to sudden onset. This led to debate with general practitioners in the audience over the difficulty of initial distinction of influenza from other viral illnesses. Dr Cotton commented that in the context of an influenza outbreak such an illness probably was influenza – in the absence of an outbreak probably not. Assessment of patients at home would usefully use the CURB 65 approach using confusion, high respiratory rate, low blood pressure and aged over 65 as severity markers. In addition availability of pulse oximetry might identify the younger patient progressing to viral pneumonia.

Dr Irvine explained the work in which she had been involved over the previous 6 years in planning for possible scenarios of pandemic flu. This involved a comprehensive structure of groups and committees covering various aspects of medical and social services within the Greater Glasgow area. She was an enthusiastic proponent of planning to improve the effectiveness of response should a pandemic occur. She outlined 3 separate planning scenarios which represented moderate, severe and worst case pandemic events. The moderate corresponded approximately to the 1957 and 1968 pandemics and the severe with 25% of the population affected and 1.5% case fatality ratio was approximately equivalent to 1918. She was dubious about the benefit of planning for the worst case scenario with a 50% incidence and a 2.5% case fatality and perhaps implied that discussions of such scenarios might risk an element of scare mongering. A severe pandemic would mean for Greater Glasgow and Clyde at the peak of infection a weekly toll of 65,000 cases and 970 deaths. The pressure on the Health Service is inevitably increased by an estimate of 2.500 cases and 37 deaths being in Health Service staff leading to a minimum of 12% staff absence. The increased workload applies to both primary care with a doubling of GP consultations and hospital work with a 50% increase in admissions. Discussions of the sort of scenario included comment on differing possible responses from medical staff – those who would find extra work time impossible and others who would rise to the challenge presented by the workload. Dr Irvine also touched on the problem of Tamiflu and the potential difficulties of deciding how a stockpile of antiviral therapy might effectively be used and whether it would in fact make a difference to outcomes.

Finally Dr Robertson addressed broader issues arising from influenza planning. His background is as a Consultant in Emergency Medicine. He had been seconded for a period of some months to work on influenza planning and had been impressed by the extensive work already done in government to look at the implications of a pandemic across various aspects of public life – not just health and social services but maintenance of other services, provision of goods, and law and order. Much of his own work involved raising awareness of the issue particularly in medical groups around the country. There are examples of detailed planning at both international and national level. The global surveillance of influenza viruses is comprehensive and allows the possibility of vaccine development. The response in the Far East with the cull of poultry when H5N1 first arose was impressive. Local responses can be adjusted according to the characteristics of a pandemic outbreak e.g. whether young adults are substantially affected. There was particular planning to deal with young children who are super spreaders of infection presumably because of close contact. Issues of the benefit and drawbacks for example, of school closure arise. Ethical issues which may be posed by pandemic flu are being addressed by a national working party. This already has papers from the WHO addressing ethical challenges for individuals, health service groups and governments. There are inevitably huge uncertainties. In the Health Service these apply to the availability of primary care cover, the capacity of emergency departments, and the availability of High Dependency or Intensive Care facilities. However, there is the possibility of new treatments becoming available, and biological techniques in this area are advancing steadily – the characterisation of the SARS vaccine took 48 days compared to around 8 years for HIV. His final comment was an observation on excellent working relationships within the different health service and government departments involved in this planning.

Mr Ritchie in concluding the evening commented on the range of pessimism and optimism encompassed in this topic and thanked the speakers warmly for contributing to an informative and stimulating evening.