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Friday 22 May 2009 (Updated Wed 3 June 2009)

RAPID ROUNDUP: Influenza A H1N1 (human swine flu) – Experts respond (May 22 update)

OTHER ROUNDUPS: June 17 | June 12 | Initial reaction
Also available: Science Blog | Useful links

The AusSMC is collecting further reaction from influenza experts as the number of confirmed cases of influenza A H1N1 09 (human swine flu) reaches double figures in Australia – including one case where a 17 year old Melbourne boy who has not travelled has caught the virus.

Feel free to use these quotes in your stories. If you would like to speak to an expert, please don’t hesitate to contact us on (08) 8207 7415 or by email.

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Read comments from:

Professor Robert Booy, Head of Clinical Research at the National Centre for Immunisation Research & Surveillance (NCIRS) based at the University of Sydney.

Professor Raina MacIntyre, Professor of Infectious Diseases Epidemiology and Head of the School of Public Health and Community Medicine at the University of NSW. She sits on the Scientific Influenza Advisory Group to the Chief Medical Officer of Australia and is an expert in influenza and emerging infectious diseases.

Dr Jennifer McKimm-Breschkin, CSIRO Chief Research Scientist and Project Leader in Virology at CSIRO Molecular & Health Technologies in Victoria.

Dr Nikolai Petrovsky, Research Director of Vaxine Pty Ltd

Dr Alan Hampson, Chairman of Influenza Specialist Group.

Professor Bill Rawlinson from the University of New South Wales. He also works in the Department of Virology at the Prince of Wales Hospital in Sydney.

Dr Heath Kelly, Head of the Epidemiology Unit at the Victorian Infectious Diseases Reference Laboratory and Associate Professor in the School of Population Health at the University of Melbourne

Dr John Carr, a pig veterinary specialist and senior lecturer in intensive agriculture at Murdoch University’s Dept of Production, Animal Health and Medicine in WA. He is also a key contact at Portec Australia, which promotes the welfare and wellbeing of pigs.

Dr John Carr is a pig veterinary specialist and senior lecturer in intensive agriculture at Murdoch University’s Dept of Production, Animal Health and Medicine in WA. He is also a key contact at Portec Australia, which promotes the welfare and wellbeing of pigs. ISSUED 25 MAY

"As a pig veterinarian, we must be careful about terminology. This is Influenza A (H1N1) – this influenza virus is not “swine flu”. The only pigs who have contracted this condition got it from man. Swine Influenza is a condition in pigs caused by a related – but different – influenza virus. There is no evidence that pigs have this virus or that they can infect man once they have the virus. Note there are no reports that other workers in Canada have contracted the virus from the pigs. Referring to this virus using its “comic” name is causing enormous damage to the peoples confidence in pork products and thus the pig industry. This is totally unjustified.

In addition, the Australian pig is totally free of all influenza viruses and are not a threat to man.

The media has a responsibility towards accurate reporting and should only refer to this virus by its official term A(H1N1). We do not want a repeat of the Egyptian response to killing its entire pig industry or the Thailand banning of Australian pork products - when Australian pork is the safest in the world."

Professor Robert Booy is Head of Clinical Research at the National Centre for Immunisation Research & Surveillance (NCIRS) based at the University of Sydney.

“There is increasing evidence that this virus may be little more deadly than standard garden variety annual influenza. However given its novelty, there remains a real concern that a larger proportion of the population than usual will become infected this winter, so even if it is no more deadly, it will still hospitalise and kill potentially many more people. Mathematical reasoning and modelling both suggest that even in Mexico there are probably far more milder and even asymptomatic cases than we realise or have proven.

Now that the virus is spreading in many countries, the number of infected is rising logarithmically and given there must now be 10s and 100s of thousands infected, the risk of further mutation in the virus rises under the immune pressure of humans and the drug pressure of treatment. Once you have enough virus out there, evolution is simple, it is statistics, it's chance combined with pressure. It is possible that with lots of immune pressure on it, it could change to the point where it is more novel and particularly more nasty.”

JUNE 2 Update: Robert Booy has also written a Science Blog on the hype behind swine flu.

Professor Raina MacIntyre is Professor of Infectious Diseases Epidemiology and Head of the School of Public Health and Community Medicine at the University of NSW. She sits on the Scientific Influenza Advisory Group to the Chief Medical Officer of Australia and is an expert in influenza and emerging infectious diseases.

“I think none of us working in the field of flu thought it was ever possible to keep H1N1 swine flu out of Australia. Some of the modeling that we did at the beginning of May and end of April showed that we would almost certainly have the first confirmed case in Australia by the beginning of June and in fact it has happened earlier than that in May. Now that there has been cases of transmission within Australia, almost certainly H1N1 swine flu will be the predominate circulating influenza in Australia this winter. I think we will be activating all our plans to try and contain the epidemic. If there is evidence of sustained transmission over winter that will also change the WHO pandemic alert phase.

The main interventions we are looking at are categorised into pharmaceutical and non pharmaceutical interventions. On the pharmaceutical side we rely on vaccines but there will be a delay in the development of a matched vaccine with August being the earliest time which we can expect to see a vaccine. Antivirals are the other mainstay and they are particularly important early before the vaccine is available and can be used as prophylaxis or treatment. Healthcare workers and front line responders are the highest priority because maintenance of essential services and our healthcare services will be of utmost importance.

On the non pharmaceutical side we will look at several measures such as social distancing and this includes the closure of schools, which has to be done very early in the epidemic to be effective, it is too late if you wait for the peak of the epidemic. The emphasis will move from the border control and quarantine measures, which are important in the delay phase, to other measure that are important in the contain phase where we really want to minimize the impact of the epidemic in the community.

I think people should also be aware of measures like not going to work if you are sick, not sending your children to work if they are sick because the workplace and schools can be one of the biggest sites of transmission. Seeking medical advice early as antivirals are only effective within 48 hours and using other non pharmaceutical measures like hand washing, proper hand washing with soap and water, which has been shown to be highly effective in prevention of respiratory viruses and other infections, as well as the use of facemasks where appropriate."

Dr Jennifer McKimm-Breschkin is a CSIRO Chief Research Scientist and Project Leader in Virology at CSIRO Molecular & Health Technologies in Victoria

Does this mean swine flu is well and truly here?
“Yes, in the immediate future and for at least the coming winter. We are seeing rapid spread globally. It is already in more than 40 countries, with more than 11,000 cases confirmed by a diagnostic test. As this is only the number who have had samples taken and sent to a laboratory for testing this is probably only the tip of the iceberg of the total number of cases, since many people will not have been tested. Certainly the numbers are grossly underestimated in the USA, since they are now mainly testing only those with more serious illness in many states.”

What does this mean for our coming winter flu season?
“As long as it doesn't mutate it means we will have four main strains of "seasonal" flu circulating in the community, instead of the usual 3 strains. By symptoms they may be indistinguishable. But even with seasonal flu it is estimated there are several thousand deaths in Australia each year, so you would not expect its death rate (based on its symptoms at the moment) to be any less. However if it mixes with any of these other circulating strains we cannot predict whether it will become more or less infectious, or more or less virulent. There are concerns that it may mix with one of the seasonal flu strains which is already resistant to Tamiflu, thus generating a strain for which there is no vaccine and for which Tamiflu treatment would not be effective.”

What is likely to happen now that we have several cases in Australia?
“Since it is still spreading globally we will continue to see new cases coming in from overseas, as well as local transmission, as has already happened here in Victoria. Due to its global spread we are past the stage of being able to contain its spread, since it seems to be highly infectious, and there is clearly a susceptible population with no immunity.”

What can be done to limit its spread?
“Standard hygiene of covering mouths and noses when sneezing and coughing and washing hands can help reduce spread. Also clearly staying at home can help limit the numbers of contacts. Spread, particularly to close family/household contacts, can also be minimised by preventative treatment with either Tamiflu or Relenza where appropriate.”

Dr Nikolai Petrovsky is Research Director of Vaxine Pty Ltd

“It is now certain that Australia will experience a major epidemic of the ‘swine flu’ H1N1 strain alongside more typical seasonal flu this winter season. Swine flu is at least if not more contagious than seasonal flu strains and so will spread far and wide across Australia. Limited background immunity to the new swine flu strain means it is likely that many more people will get infected with flu than during a normal flu season, and likely lack of protection by the current seasonal vaccine means that traditionally heavily vaccinated populations like the Australian elderly will be more vulnerable than normal.

The inevitable consequence will be greater demand for hospital beds than during mild flu season and a higher than normal total number of deaths from flu in the very young and elderly - more a consequence of the greater number of people who will be vulnerable to infection during this season rather than any heightened lethality of the swine virus, which appears to be similar to normal seasonal flu strains.

Prevention remains key in protecting susceptible individuals by attention to personal hygiene and by infected individuals quarantining themselves and not infecting others while they are infectious. Whilst a vaccine is not yet available, immunisation with the current seasonal flu vaccine should be encouraged more than normal to limit total flu cases and taking pressure off hospitals by reducing preventable cases due to normal flu strains.”

Dr Alan Hampson is Chairman of Influenza Specialist Group

“At this stage it is not known how the Melbourne 17 year old contracted swine influenza; however he is recovering well in home quarantine and health officials are continuing to investigate the source of his infection. The situation in Australia has not changed greatly as there are still only a small number of confirmed cases and the number of people currently being investigated is quite small. Our health authorities are progressively implementing the Australian Health Management Plan for Pandemic Influenza as required, a plan that has been developed and refined over the last decade. With a substantial supply of antivirals and other emergency supplies they are well placed to delay more extensive spread in the community and to mitigate the effects of an outbreak.”

Please contact Hayley Dowling 02 9928 1521/ 0404 852 884 or Sarah Cornhill on 02 9928 1504/ 0408 978 629 for any media interviews with Alan Hampson or other Influenza Specialist Group Directors.

Professor Bill Rawlinson from the University of New South Wales. He also works in the Department of Virology at the Prince of Wales Hospital in Sydney.

“The number of cases in the US is increasing significantly, there are almost 5,500 cases so far. The case fatality does seem to be at the lower end of what we believed. So it does seem to spread easily but it does not seem to be as fatal as what we first were concerned about, based on the very first data. There has been some recent data that suggests the vaccine doesn’t offer cross protection - so that the human vaccine is not offering cross protection, although the information from CDC to date is that the antivirals are effective against the influenza A H1N1 09 human swine strain. Importantly with the cases in Australia, the case definition has changed so that it is not only someone returning from overseas but its somebody in Australia who has been in contact with a known case of influenza A H1N1 09 human swine infection. That change was made yesterday. In a public health sense that suggests that we now think that swine flu is here.

The implications are still not certain but it does seem likely that there be more cases of influenza A H1N1 09 human swine in the winter flu season in Australia."

*We have been advised that Bill will not be available for interview or further comment and that all requests will be handled through the NSW Department of Health – 02 9391 9121

Dr Heath Kelly is the Head of the Epidemiology Unit at the Victorian Infectious Diseases Reference Laboratory and Associate Professor in the School of Population Health, University of Melbourne

“The population-based impact of infection with swine origin influenza A (H1N1) virus infection is not yet clear as we are still in the early days of the epidemic, especially in Australia . We are currently in the process of comparing the available data on swine origin influenza A (H1N1) virus infection overseas with the previous seasonal influenza A (H1N1) virus infection in Australia in 2007-2008 to assist with forward planning for this current outbreak. Influenza A (H1N1) virus infection seems to be predominantly a disease of younger people, whether the virus was of swine or human origin Disease outside Mexico is associated with a relatively low case fatality rate.”