April 28, 2009

experts discuss swine flu

Swine flu has continued to spread around the world, with the first cases being confirmed in the UK (in Scotland). The WHO has raised the global pandemic threat level from 3 to 4 (out of a possible 6) although experts continue to urge caution over the scale of the threat.

Prof Ronald Cutler, Deputy Director of Biomedical Science, Queen Mary, University of London, said:

“There is little evidence as to the effectiveness of facemasks and respirators for the control of influenza especially in the control of swine influenza A (H1N1) virus. There is a great variation also in the design of masks, close fitting or sculptured masks should be used in combination with other preventive measures, such as maintaining good hand hygiene and avoiding close contact.

“This recent outbreak of swine flu, as with the previous avian flu outbreak, once again shows how influenza takes advantage of situations where people are living in poverty and close to animals. The rapid dispersal of the virus to different countries also demonstrates how these organisms make use of modern travel.

“Avian flu is to my mind currently held in check by its relatively poor ability to cross into and between humans, however once established it was more rapidly dangerous than the current swine flu and for treatment to be effective it had often to take place in the first few hours. Swine flu does transfer into and between humans but if identified can be effectively treated with antivirals sometimes days later. This allows countries that have stockpiled these agents to have an effective response but it does not help poorer nations that do not and it is in these countries that this disease could spread and further develop.”

Gail Lusardi, Senior Lecturer, Faculty of Health Sport and Sciences (HESAS), University of Glamorgan, said:

“FFP3 facemasks are termed ‘respirator masks’. They are different from other facemasks as they have an efficient filter layer to stop the inhalation of virus particles from droplets of saliva and respiratory secretions from an infected person. The mask must fit correctly and key healthcare staff should have been ‘Fit Tested’ in preparation for a pandemic influenza outbreak. The mask can be worn continuously for up to 8-10hrs but must be replaced if it is taken off at any stage. Masks alone will not prevent spread of the influenza virus and basic hygiene measures like hand washing, safe use and disposal of tissues and cleaning of environmental surfaces are key to preventing infection transmission. UK governments and Hospital Trusts will already have some emergency stocks of these masks in preparedness.”

In answer to specific questions from journalists, Prof Peter Dunnill, Chairman, The Advanced Centre for Biochemical Engineering, University College London, said:

“Can you comment on early detection methods and vaccine synthesis?
“This is a very early stage to make judgements. However, the indications that this is a virus composed of human, avian and swine elements may be helpful if the human component is recognised by those who have had past influenza infections.

“Historically, some pandemic viruses have been mild in the first phase but later as selection of the fittest works on the virus they can be more virulent.

Is screening at airports a waste of time?
“The problem of screening at airports is that people can be infectious with influenza before they have a high fever. So, heat scanning may not work well. Human nature is also such that people suspecting their state may wish to just get home to the health system they trust so questionnaires may not be completely trustworthy.

Why does the flu seem to be less deadly outside of New Mexico, is it the disease changing or simply better healthcare in more developed countries?
“The Mexican fatalities may not be any higher as a proportion than elsewhere. Until suspicion would have arisen by say the unusual number of healthy people succumbing it would be assumed this was just a bad seasonal flu year, and we are in a period where vaccines have not been well matched to all the seasonal viruses.

What are the estimates of the timeline to develop a vaccine, should it be needed?
“The issue of making a vaccine is difficult. At this point only classical methods can be used for manufacture. These use live hens eggs inoculated with either the virus or an engineered form if the natural virus kills the eggs. The process is laborious and for seasonal vaccines, made up of 3 different viruses, manufacture takes about 6 months. That means companies must be entering the campaigns for next autumns Northern Hemisphere vaccine. Working up a virus seed which the US Centre for Disease Control and others are active on will take time so there will be difficult decisions on priority between people at risk of seasonal flu and those at risk of swine flu. A quadrivalent autumn vaccine is conceivable but complex to achieve. Vaccine is given to an individual at a point where they are well – not like a medicine where they are ill. Therefore safety is even more dominant. This tends to make procedures slow.

“Because the swine flu is potentially here now there is no time to consider any non-conventional approach. However, based on calculations done in relation to H5N1 the global capacity for providing vaccine at its most optimistic, and using chemical activators or adjuvants with the vaccine, is less than 10% of the worlds people. Only 9 countries, most in Europe have large influenza vaccine capacity and it is only adequate for a proportion of their own populations – those at risk of seasonal flu. At present the USA is not self dependent but is putting in place new cell culture which will give it self reliance and will be less subject to bacterial infection than hens eggs. If the swine flu is not too severe the outcome will be sad in resulting in deaths potentially in some young healthy people but the majority will be fine. If it mutates to be more severe or if a more virulent virus pandemic occurs, people may wish for more government financial commitment. Only the US government can honestly say it is trying hard in this regard.”

Further comments from Prof Dunnill:

“The US under President Bush’s leadership has invested far more heavily in pandemic preparedness than the EU and leads in the education of the public and business. If the swine flu pandemic causes the issues to be addressed in Europe with more candour it would be at least a valuable outcome. There are other vaccine options but they may entail using newer vaccines and the public needs to have a say in what it would wish. If the fatalities are less than 1% of the global population, i.e. 65 million, do people prefer an extremely low risk vaccine taking more than 6 months to produce similar to the very safe seasonal ones. If fatalities are higher are they prepared to use newer vaccines, tested well, but with less history of use.

“Education and information is important because even a medium level influenza pandemic can be very disruptive. As doctors, nurses, food delivery drivers, power station and water supply staff fall ill there is a tendency for services to falter.

“One of the prime issues for the media is to watch how well government does with the specifics. There are a number of high level committees and many pages of broad policy guidance but the acid test will be how this pans out in practice. That is made especially critical because so called bird flu (H5N1) has not gone away and because it seems set to remain a “pure” avian virus slowly gaining more capacity to infect humans it could be much more serious. The human system will have nothing to recognise and people’s abnormal immune response could be much greater. There are indications in Indonesia and Egypt currently of more human to human infection, albeit to a still limited extent. Therefore, how the authorities deal with a swine flu pandemic will be a guide to their capacity to cope.

“One of the cornerstones of policy of all governments has been the stockpiling of anti-flu drugs, particularly Tamiflu and Relenza. Because anti-flu drugs only protect as long as they are taken the government stocks, limited by cost and shelf life, will probably be issued to front line personnel if they become sufficiently feverish. (If received in the first few hours anti-influenza drugs diminish the symptoms and duration but effectiveness drops quite quickly with delay). Such staff may still require sick leave but compared to a situation without effective drugs the outcome is still much better. There will be no more effective approach up to the point where vaccine is produced, distributed, vaccination is organized and people’s immune systems respond.

“It has come as a surprise to many that within the last year the seasonal influenza H1N1 virus (which differs from swine flu H1N1) has become almost totally resistant to Tamiflu. The cause is unknown but may relate to the wide use by WHO of “Tamiflu blanketing” of all the villagers in say an Indonesian location where there has been a confirmed H5N1 human case, usually a death. It is likely that some villagers have at the time been infected by seasonal H1N1 (which shares roughly the N1 with H5N1). This may be a situation which rapidly drives resistance. By the same token we may see the swine flu H1N1 become Tamiflu resistant. That would deprive governments of a key protection for front line staff.

“In terms of advice to the public, US official government advice seems sensible. People cannot realistically shut themselves off from a pandemic in the modern world and when the several waves may last 18 months. They can make sure they have sensible stocks of food and essentials such as disinfectant and tissues. If individuals, their families and those close to them require medication it is sensible to make sure they are not running out of stock, simply because there could be delays in the international supply chain. Surgical masks may be comforting but moist breadth clogs them and most air passes between cheek and nose. If patients can tolerate them they reduce the possibility of infecting carers via coughing. Removal of masks can easily contaminate the face and transfer virus to the eyes.

“The main message for the media is this. You are the most crucial agency for asking questions of the bureaucracy. The profile of swine flu will allow searching questions to be asked on the detail of pandemic preparedness not just the broad assurances. Please press for answers. Not only do the personal tragedies of lives lost require that but the disruption to frail economies makes flexible and responsive policies crucial.””