THE DECLARATION of the first global influenza pandemic in over 40 years is not unexpected. With almost 30,000 cases of Influenza A (H1N1) confirmed across 74 countries and some hundreds of thousands of people actually infected, the disease probably met the technical definition of a pandemic some weeks ago.
And given the extreme warnings about the potentially catastrophic effects of an avian (H5N1) flu pandemic for the last number of years, the public could be forgiven for greeting the World Health Organisation (WHO) declaration with alarm. However, this would be a mistake. The models for avian influenza assumed a death rate more akin to the severe 1918 Spanish flu than the low mortality we are seeing with the 2009 swine flu pandemic.
In fact, the pandemic declaration has been made on largely geographic grounds. The infection is now spreading on a number of continents, with clear evidence of human-to-human transmission among people who have not traveled to either Mexico or the US. But there is no evidence that the illness it produces has got any worse. Raising the pandemic alert level from phase five to six, its highest level, will not impact on the public here. However, the decision will allow pharmaceutical companies to accelerate their efforts to produce an effective vaccine against the novel virus.
The WHO decision is likely to have a greater impact in southern hemisphere countries such as Australia and Chile. It is winter south of the Equator, with conditions ripe for the rapid spread of respiratory viruses such as influenza. Chile saw a notable spike in the number of confirmed cases this week, while the Australian city of Melbourne also has been hit hard. It may be that the national authorities will consider moves aimed at discouraging public gatherings, such as suspending classes in schools and universities, initiatives consistent with phase six status guidelines. The disease may also represent a particular threat in poor countries.
The situation in the southern hemisphere is a strong indication of what we can expect in this part of the world from October onwards. The rate of infection will speed up considerably with a likely race developing between the spread of the H1N1 virus and the rate of inoculation of the population with an effective vaccine.
Pandemics traditionally hit in successive waves, so it is possible the second wave of infection will coincide with the onset of winter here. This could place considerable short-term strain on our hospitals, given the likelihood that those with pre-existing chronic disease may require admission. A real fear among public health professionals is that the virus could mutate and produce a new strain with a higher mortality.
In the meantime, an analysis of cases identified in some 30 European states has shown the H1N1 influenza virus predominantly affects those aged 20 to 30. It carries a two per cent complication rate, meaning one in 50 victims develop a bacterial pneumonia or other medical complication as a result of contracting the flu. But the mortality rate is low, a welcome characteristic we must hope will not change as winter approaches.