There are up to 500 strains of influenza viruses and they constantly change and evolve. They are normally highly species-specific and only rarely spill over to cause infection in other species. (Farndon, 2005)

Influenza type A virus affects humans and animals. One of them, the avian influenza virus has been recorded to affect birds and human. Only four, of the hundreds strains of avian influenza virus, are known to have caused human infections. In general, human infection with these viruses has resulted in mild symptoms and very little severe illness, except the highly pathogenic H5N1 virus ("Avian Influenza", 2006).

From 278 reported cases of H5N1 avian influenza since 2003, 168 died. Health experts began to fear that a new and deadly flu pandemic was imminent.

This paper will discuss and present the global size and problem of H5NI avian influenza, risk factors influencing the frequency and distribution of the disease, and prevention and control measures in Australia.

The Size of the Problem in Human

Countries where the H5N1 virus infected humans include Azerbaijan, Cambodia, China, Djibouti, Egypt, Indonesia, Iraq, Lao PDR, Nigeria, Thailand, Turkey, and Vietnam.

There is the risk that the virus will start a pandemic, through genetic material exchange between human and the viruses, during co-infection of a human or pig. Virus mutation is also another possibility (World Health Organization, 2006).

In a pandemic occurs, between two million and 50 million deaths worldwide was predicted by experts. ("Q&A: Bird Flu,"2007)

In humans, the reported symptoms of H5N1 influenza virus have ranged from typical influenza-like symptoms to eye infections (conjunctivitis), watery diarrhea, pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications.

On 24 March, 2006, there were 42 cases reported to the WHO and there were 15 cases on 24 March, 2007. The global incidence and prevalence rate could not be calculated as the disease was rare and patchily spread.

Incidence rate by age shows that half of the H5N1 cases occurred in people under the age of 20 years, 90% of cases occurred in people under the age of 40 years. Those between the age of 10 to 19 year-old is the largely group affected and 70 year-old and above the least ("Avian Influenza," 2006).

A total of sixty percent or 168 out of 278 people who contracted the virus have died. The Case Fatality Rate (CFR) was highest in 2003 (100%), followed by 2004 (70%) and 2006 (69%). However, the total number of occurrences and deaths was highest in 2006 when out of 116 cases, 80 people died. Please refer to appendix for additional yearly CFR and country specific CFR.

The Factors Determining and Influencing the Frequency and Distribution of the Disease

The risk from H5N1 virus is generally low to most people. However, contact with infected birds or surfaces that have been contaminated with their excretions, increases the risk factor. The virus can survive for long periods in the tissues and faeces of diseased birds and in water, especially when temperatures are low. ("Avian influenza," 2006)

Exposure to an environment that may have been contaminated by faeces from infected birds is a second, though less common, source of human infection. To date, not all human cases have arisen from exposure to dead or visibly ill domestic birds. A history of poultry consumption in an affected country is not a risk factor, provided the food was thoroughly cooked and the person was not involved in food preparation ("Avian Influenza," 2006).

For unknown reasons, most cases have occurred in rural and pre-urban households where small flocks of poultry are kept. Very few cases have been detected in presumed high-risk groups, such as commercial poultry workers, workers at live poultry markets, cullers, veterinarians, and health staff caring for patients without adequate protective equipment. Research is urgently needed to better define the exposure circumstances, behaviours, and possible genetic or immunological factors that might enhance the likelihood of human infection ("Avian Influenza,"2006).

Prevention and Control in Australia

Australia is one of the most prepared countries in the world to respond to an outbreak of H5N1avian influenza or any influenza pandemic and that $555 million has been provided to ensure that Australia is prepared.

An episode of H5N1 infection would trigger the Australian Management Plan for Pandemic Influenza (AHMPPI). Victoria also has a Pandemic Influenza Plan, which details the steps that will be used by state government agencies and health services to manage an outbreak. The Australian Veterinary Emergency Planis designed to manage bird flu outbreaks among bird populations such as poultry farms. ("Bird Flu," 2006)

There are no reports of the current H5N1 flu strain in Australia, either among birds or people. There were five previous bird flu outbreaks in Australia among commercial flocks, all of which were contained and eradicated. The last outbreak was in 1997 in Tamworth in New South Wales. ("Bird Flu," 2005)

The AHMPPI includes Surveillance, monitoring and reporting; Infection Control; Quarantine; Border control and public awareness and education. It includes purchase of antiviral drugs, vaccines, thermal imaging screeners, funding for the improvement of the nation's infectious disease surveillance.

Posters and scripts to be used by local health and community workers for Aboriginal and Torres Strait Islander Health communities. They focus on the human health risks of avian influenza in wild birds in Australia. (Department of Health and Ageing, 2006)

Containment of disease and maintenance of essential services is the focus of the plan. In the early stages of a pandemic, intensive efforts will concentrate on containing the pandemic to make time for a vaccine to be produced. Strategies include reducing traveler numbers to Australia, social distancing and infection control measures, short term home quarantine for those exposed to the virus and the targeted use of antiviral drugs.

Conclusion

The H5N1 virus killed 60 percent of those infected. Most had very close contact with infected birds or their body fluids, or through eating them raw.

Between two million and 50 million deaths worldwide was predicted by experts if a pandemic occurs. ("Q&A: Bird Flu,"2007)

Research studies to test a vaccine to protect humans against H5N1 virus began in April 2005. The vaccine has been shown to produce an apparent protective immune response but only at an unusually high dose and only in just over half of the people vaccinated. Given the world's limited capacity to produce vaccines, it means that only 1.25% of the world's population could be vaccinated if it was required and only half of those would be immunized. ("Avian influenza," 2006)

There are no reports of the current bird flu strain in Australia, either among birds or people. Australia is one of the most prepared countries in the world to detect and manage Avian Influenza if it enters the country. Australia's plans and strict quarantine policy work together to keep Australia safe.

Since there is a possibility of an avian flu H5N1 pandemic occurring and a vaccine with full immunogenicity is not yet found, preventive measures are the keys in keeping minimal outbreak in a country.