ANALYSIS:As early concerns about the virus ease, new fears emerge, writes DR MUIRIS HOUSTON, Medical Correspondent
ALTHOUGH CONCERNS about the severity of the H1N1(A) virus continue to lessen, with more than 1,000 cases in 20 countries there is nothing to suggest the new strain of influenza is anything but highly transmissible.
There is evidence of human-to-human transmission among people living in Britain and the US who have never been to Mexico. And the excellent scientific detective work carried out in Canada showing a “reverse” transmission of the virus from an agricultural worker to a pig reinforces the belief that the new strain is highly mobile and adaptable.
The news that the infected farm worker had spread the influenza virus to pigs in Alberta has been cited by a World Health Organisation food scientist as increasing the risk that people who work closely with pigs on farms and slaughterhouses could catch the H1N1 virus.
Analysis of the new strain shows it as a hybrid of swine, bird and human influenza. US scientists have shown a link between six segments of the Mexican strain of H1N1 and previously identified swine viruses from North America.
Two of the eight segments are linked with swine viruses isolated in Europe/Asia.
There is some concern among scientists that if an animal is infected with two strains of the virus at once, genetic material may be swapped freely between them to produce a deadlier version of the disease.
The H and N nomenclature used to identify a particular Influenza A refers to proteins on the surface of the virus. One is called neuraminidase (N) and it enables the replicating influenza virus to break away from the cell it initially invaded and to spread throughout the body.
There are nine types of neuraminidase. The other is haemagglutinin (H), of which there are 12 basic types; it is the means by which the virus enters the cells of its host.
Antiviral drugs act as neuraminidase inhibitors and prevent newly formed influenza particles from escaping infected cells, thereby interrupting the spread of infection within the body.
Are comparisons with the 1918 pandemic reasonable or simply scaremongering? Certainly the high percentage of young people affected is reminiscent of the world’s worst ever flu pandemic. The time of year – coming after our traditional flu season – is also similar.
And for those of a pessimistic nature, the fact that the initial 1918 wave of infection in July was mild but was then followed in October by a far deadlier second wave, is a valid reason for concern.
However, public health authorities have the situation well under control and we are a long way from any doomsday scenario.
