The Department of Health and the HSE have contingency plans in place to deal with an outbreak of bird flu in Ireland, writes Darina O'Flanagan.
Avian influenza, or "bird flu", is a contagious disease of animals that normally only infects birds. Chickens, ducks, geese, swans, turkeys, shorebirds, gulls and other birds can be infected with avian influenza. Waterfowl are the natural reservoir for avian influenza viruses. Two subtypes of avian influenza (H5 and H7) are capable of mutating into highly pathogenic forms, which can cause serious illness and rapid fatalities in poultry.
However, as recent events have demonstrated, with particularly tragic results for one unfortunate family in Turkey, humans can be infected with avian influenza viruses. The cause for concern, of course, is that the H5N1 virus can mutate and gradually adapt to humans, or that it mixes in a person who is simultaneously infected by both a human influenza virus and an avian virus, and so can become transmissible from human to human. Either way a global pandemic would result as humans have no immunity to the H5 antigen.
The current outbreaks of H5N1 highly pathogenic avian influenza, which began in southeast Asia in mid-2003, have been the largest and most severe on record.
Outbreaks were initially reported from Korea, Vietnam, Japan, Thailand, Cambodia, Laos, Indonesia and China. This was followed by Malaysia, Russia, Kazakhstan, Mongolia, Turkey, Romania, Croatia and Ukraine. Japan, Korea, Malaysia and Croatia have announced control of their poultry outbreaks. In the other areas, outbreaks continue with varying severity.
In Turkey, poultry outbreaks are now known to be occurring in several parts of the country, in at least 10 of the country's 81 provinces. Extensive culling is under way, but with many subsistence farmers with small backyard flocks, the challenge is enormous. Turkey has now reported 14 confirmed cases of H5N1, mostly in children.
The evidence to date from Turkey indicates that direct exposure to sick or dead poultry is the source of infection. There is no evidence that the virus has increased its transmissibility or is spreading from person to person. Further information is awaited from the World Health Organisation/European Centre for Disease Control (ECDC) team on site about transmission and also on the genetic composition of these recent strains. This should be available in the coming days.
What does this mean for Irish holidaymakers?
Basically the advice remains as before. There is no travel restriction to any country currently experiencing poultry outbreaks.
Irish tourists to Turkey and other affected countries are advised, however, to avoid contact with live poultry and wild birds, to avoid visiting live animal markets and poultry farms. They should avoid contact with surfaces contaminated with animal droppings. They should not eat undercooked or raw poultry, egg or duck dishes. As anywhere, frequent hand-washing is encouraged. It is not recommended that travellers take anti-virals with them unless they may be exposed to avian influenza through their work.
The clinical features of H5N1 include sudden onset of fever, cough , aches and pains, sore throat, breathlessness and diarrhoea. Almost all patients have a viral pneumonia at the time of hospital admission. Unfortunately many progress to respiratory and multi-organ failure and of the 147 cases reported to WHO, 78 have proven fatal.
The initial symptoms are mostly similar to symptoms of ordinary influenza so returning visitors with these symptoms from affected countries will be asked about close contact (within a metre) with live or dead domestic fowl or wild birds. Although swine can also be infected with avian influenza, this has not been common in these H5N1 outbreaks. Patients with a history of exposure and symptoms as above will be sent for tests such as throat swabs to rule out infection.
Human-to-human transmission has very rarely been reported with H5N1 and these cases have mostly been limited to close family contacts who have cared for very ill relatives.
Therefore there is no need to worry about casual transmission from other humans with signs of mild respiratory illness in Turkey or elsewhere.
Antiviral drugs can be effective if started early enough in the illness. They are not usually considered effective after 48 hours from the onset of the illness.
In Ireland the Department of Health and Children and the HSE are stockpiling antivirals. Six hundred thousand treatment courses of Oseltamivir (Tamiflu) are already in the country and another 400,000 treatment courses will be supplied later this year. Many countries, including Ireland, are also seeking additional doses of the other suitable antiviral drug Zanamivir (Relenza) and orders have been placed for these. H5N1 vaccine for humans is still undergoing clinical trials and is not yet commercially available.
A limited order of this vaccine for key health workers is being actively pursued by the Department of Health.
It is possible that the virus would mutate further and this vaccine would become ineffective. The Department is, therefore, also pursuing an advanced purchase order for a pandemic strain vaccine for the whole population. This vaccine cannot be manufactured until a strain with human-to-human transmission capabilities emerges.
In summary what are the risks to Ireland?
We are hopeful that as we are not on the main migratory pathways of waterfowl from affected countries, we will not get an avian outbreak here.
However, some species do migrate here and the Department of Agriculture, Department of Health and the HSE have contingency plans in place for outbreaks of avian influenza. As the poultry industry in Ireland is organised very differently, we would hope that in such an event human exposure would be very limited. Again, contingency plans to manage human cases following avian outbreaks are in place. The next threat, of course, would be the emergence of a virus from the affected countries that is transmissible from human to human. It is difficult to be precise about this threat.
Obviously the greater the number of human cases of H5N1 the greater the risk. The possibility that migratory birds will next spread the disease to Africa is a major concern. As in southeast Asia and more recently Turkey, traditional practices in areas affected by rural poverty favour the slaughter and home consumption of birds when signs of illness appear in flocks. In addition, many poor families depend on poultry as a source of nutrition for their children and without adequate compensation will resist the culling efforts of national authorities.
At a recent meeting held by WHO in Geneva in November 2005, the devastating consequences of the outbreaks in poultry were briefly described. In Asia over 150 million chickens had died or had been culled. The economic costs were estimated to go well beyond $10 billion. These costs were being felt most acutely by over 200 million small farmers, whose livelihoods had been severely affected. To date countries with limited resources have been the most severely affected by poultry outbreaks.
The challenge for the international community is how we can best support the effort to control outbreaks in affected countries, particularly resource-poor countries. The support needs to be both financial and technical.
During the meeting, France announced that it would strengthen its network of Pasteur Institutes in Asia and Africa, providing diagnostic support for both poultry and human cases.
Such financial and technical supports should be replicated by all rich countries and sustained if we are to decrease the continuing threat of human pandemic influenza from H5N1.
Darina O'Flanagan is director of the Health Protection Surveillance Centre.