Concerns about variant strains of influenza infecting children udner 10 in a number of states in the US have resulted in the CDC (Centre for Disease Control in Atlanta) requesting greatly increased monitoring (sampling, reporting, more advanced testing)
The background is quite complex "with the detection of three different serotypes (H3N2v, H1N2v, H1N1v) as well as two distinct constellations in the H3N2v cases".
Confirmation of infection with these strains is proving difficult due to limitations (limited cross reaction) with the current widely used PCR test. More costly sequencing may be required to provide definitive strain typing.
To date the CDC has tended to associate human cases with direct exposure to swine but this link has been tenuous. There is increasing evidence of sustained spread between humans - hence the request for increased surveillance.
It is likely that the existing vaccines will provide very limited cross protection. This leaves anti-virals as the first line of treatment. Development of a vaccine against a new strain has a 6 month or longer lead time. The likely presence of a number of new strains makes development of a vaccine a major challenge. It is unclear whether one particular strain will eventually dominate.
Currently the circulating variants appear to be causing relatively mild disease but with hospitalisation in some cases. It is likely that diagnosed cases are the tip-of-the iceberg.
There are indications that the diagnosis may also be underestimated due to absence of fever, normally regarded as present in cases of influenza, and hence testing not being pursued in children hospitalised with pneumonia.
Watch this space.
Regards Kangaroo1
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