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Bird flu: are we dealing with horror or hype?

Katrina Le Saux
RN RM
Student Nurse Practitioner

Avian flu, the long-awaited influenza pandemic, would seem to have become the staple diet of newspapers, radio and television broadcasts in recent months. This article attempts to unscramble the maze of advice in current circulation and provide advice and resources for primary care staff in dealing with this seemingly growing concern.
Avian flu is an infectious disease of birds caused by type A strains of the influenza virus. It was first identified in Italy more than 100 years ago, but the disease occurs worldwide. Infection can range from a mild illness through to a highly contagious and rapidly fatal disease, which has a sudden onset, causes severe illness and is rapidly followed by death.
All outbreaks of the "highly pathogenic avian influenza" have been caused by influenza A viruses of subtypes H5 and H7. Migratory waterfowl are the natural reservoir of the avian influenza viruses, but these birds are also the most resistant to infection. Domestic poultry, including chickens and turkeys, are susceptible to epidemics of rapidly fatal influenza.
Avian influenza viruses do not normally infect species other than birds and pigs. The first official documented infection of humans with an avian influenza virus occurred in Hong Kong in 1997 when avian influenza (H5N1) infected both chickens and humans. A direct transmission from birds to humans was proven, 18 people were hospitalised and six of them died. The culling of Hong Kong's entire poultry population, estimated at 1.5 million birds, to remove the source of the virus, contained the spread of disease, and most experts agree that it probably averted a pandemic.
This event alarmed public health authorities, as it marked the first time that an avian influenza virus was transmitted directly to humans and caused severe illness with high mortality. The ability of the influenza A virus to swap species or reassort genetic materials and merge is known as "antigenic shift" and results in a novel subtype different from both parent viruses. As populations will have no immunity to the new subtype, and as existing vaccines don't confer protection, antigenic shift has historically resulted in highly lethal pandemics. In order for a pandemic to occur, the novel subtype needs to have genes from human influenza viruses that make it readily transmissible from person to person for a sustainable period.

Pertinent bird flu history

  • 1918: The "Spanish flu" killed 50-100 million people worldwide over a period of two years. Research performed in America was apparently able to obtain virus samples from the dead bodies of this pandemic and suggests that it originated from the bird population.
  • 2003: Two cases of avian influenza A (H5N1) infection occurred among members of a Hong Kong family that had travelled to China; one person died, one survived.
  • 2003: Avian influenza A (H7N7) infections among poultry workers and their families were confirmed in the Netherlands during an outbreak of avian flu among poultry. There was evidence of human-to-human transmission and one person died.
  • 2005: Taiwanese finches died in quarantine in the UK. It was confirmed that they were infected with avian influenza A (H5N1) virus.

At the time of going to press, 130 people in Asian countries had caught the infection as a result of close, direct contact with infected birds; 67 subsequently died. But there is no firm evidence that H5N1 has acquired the ability to pass easily from person to person.(1)
The media has raised patient anxiety with its predictions of the horrors that await us should a pandemic occur; UN Health's David Nabaro estimating that a mutated human-to-human bird flu virus could kill between five million and 150 million people has fuelled this. The World Health Organization (WHO) has stated that it is only a matter of time until the H5N1 virus causes global chaos through human transmission, and Sir Liam Donaldson, Chief Medical Officer, said in a BBC interview that it wasn't a question of if the virus would hit, but when. WHO is estimating the likely death toll in the UK, should the pandemic materialise, to be about 50,000. The Department of Health quotes a figure of 12,000 as the number of deaths caused by ordinary influenza in the course of a year.
Andrew Cavanagh, a prominent Australian health writer, is a lone voice in suggesting that these escalated warnings should be seen as bird flu hype.

Infection
Bird flu virus spreads in several ways:

  1. Poultry saliva.
  2. Poultry nasal secretions.
  3. Poultry manure.
  4. Infected food, water, equipment and clothing.

Because pigs are susceptible to infection with both avian and mammalian viruses, including human strains, they can serve as a "mixing vessel" for the scrambling of genetic material from human and avian viruses, resulting in the emergence of a novel subtype.
It is important to remember that, if an infection occurs, the incubation period is 3-5 days.

Interim treatment
Influenza is highly infectious and is spread before the onset of symptoms. When the virus is known, the government will eventually have 120 million doses to distribute; however, no vaccine would be available until four to six months into a pandemic.
The problem in manufacturing a vaccine is that scientists have to see the flu strain in order to destroy it. In the interim, a five-day course of oseltamivir (Tamiflu) is recommended for the treatment, not prophylaxis, of patients who have a flu-like illness and fever and have been symptomatic for less than two days. The current order stands at 14.6 million doses to be delivered by the end of 2007. Oseltamivir has not been tested in a pandemic, and its possible effectiveness against a mutant strain of H5N1 virus is unclear. There is suggestion that zanamivir (Relenza) should also be stockpiled. When a pandemic strain emerges, doctors will see which groups are most at risk and allocate the stockpile accordingly. Health workers, the elderly and people with weakened immune systems are likely to be among those at the top of the list.

Contingency plan
The DH has published a contingency plan,(2) which runs to 177 pages. They have also produced a 24-page operational guidance document, which helps to make the issues clearer.(3) One of the main concerns is the amount of disruption in the workplace that could be caused by a flu pandemic and the knock-on effects this might have for the delivery of health and other essential services. An assumption is made that 25% of the population will develop flu over a 12-week period, compared with a seasonal attack rate of 5-10%. The operational guidance mentions the possibility that schools could be closed, and additional absences could occur from work because healthy people will be needed at home caring for either children or the sick.
The operational guidance does also have some constructive suggestions to make:

  • Good information gathering will be important, so the diligent use of Read codes for confirmed influenza (H27 - there are also various subcodes for influenza with complications) and flu-like illnesses (H27z-1) could be helpful.
  • Patients with confirmed or suspected influenza should be encouraged to stay at home in order to avoid spreading the virus.
  • Surgeries should be prepared to cancel everything nonurgent (eg, smears, chronic disease checks) if the situation gets very difficult and an effective vaccine is developed, as the most probable mode of delivery will be through primary care.
  • Small surgeries need to be prepared to help one another out, by sharing either facilities or staff.
  • Good hygiene could help to delay or prevent the spread of infection through diligent handwashing and possibly using face masks.

Conclusion
Although the current climate of opinion is making the assumption that it is merely a matter of time before the influenza pandemic arrives upon our shores, there still remains a possibility that disaster could be averted. As healthcare professionals, the public will turn to us for advice, explanation and guidance as to what a possible pandemic will mean in practical terms and for the latest updates on vaccinations.

References

  1. Department of Health. Available from: http://www.dh.gov.uk/
  2. DH contingency plan. Available from: http://www.dh.gov.uk/assetRoot/04/12/17/44/04121744.pdf
  3. DH operational guidance. Available from: http://www.dh.gov.uk/assetRoot/04/11/10/82/04111082.pdf

Resources
Getting ahead of the curve: a strategy for combating infectious diseases. A report by the Chief Medical Officer, Department of Health; 2002. Available from: http://www.dh.gov.uk/assetRoot/04/06/08/75/04060875.pdf

DH bird flu advice
W:www.dh.gov.uk/pandemicflu

CMO website
W:www.dh.gov.uk/cmo

WHO
W:www.who.int/csr/disease/avian influenza/en/

HPA
W:www.hpa.org.uk/infections/topicsaz/avianinfluenza/menu.htm

How to prevent bird flu
W:www.howto preventbirdflu.com