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Paradigm Shift Intervention Monitoring
There have been reported four serious
cases of confirmed hospitalized AnH1N1 influenza virus, they are all
men aged 24-57 years who had no risk factors and were admitted to the
ICU between 5 and 11 December.
Up to week 49/2010 there have been nine severe cases confirmed and hospitalized, all men and 89% without risk factors.
The figures reveal all of the flu victims were aged under 65 and six were under 18 years-old.
At least eight of the 17 fatal cases was in an "at-risk" group - such as somebody with diabetes or asthma - but none were pregnant.
The above comments from week 49 reports out of Spain and the United Kingdom highlight severe and fatal H1N1 cases this season. Spain is trailing the UK, and the week 49 report from the UK is trailing the HPA report due to the spike in severe and fatal cases in the past week.
As seen last year, these cases are heavily concentrated in patients less than 65, but this year the frequency of cases without underlying conditions is on the rise. The underlying conditions are broadly applied, although the more severe and fatal cases are concentrated in the cases with more severe conditions. Thus, obese cases are concentrated in the morbidly obese and most pregnant patients are in their third trimester, but the “underlying condition" category includes all obese patients and all pregnant patients, so the frequency of severe cases with these conditions is high. However, as seen above, even with the broad definition of underlying condition, the majority of the cases cited above do not have underlying conditions.
The increased targeting of healthy young adults, as well as the rapid rise in severe and fatal cases, when the H1N1 levels in the entire population are relatively low, raises concerns that the H1N1 has changed and become more virulent in the UK and Spain, with similar results to follow in other countries in the northern hemisphere.
This increased virulence has been noted previously for H1N1 with the receptor binding domain change D225G, which was strongly associated with severe and fatal cases last season. A change in the frequency of H1N1 with D225G could dramatically increase the frequency of severe and fatal cases. This type of change could be linked to other receptor binding changes that would be seen in the sequences associated with these recent cases.
D225G was predicted in severe and fatal cases in Ukraine and was present in all four fatal cases when initial sequences were released. It was also correctly predicted to be in death clusters, such as the fatal cases at Duke Medical Center. Similarly, D225G was in two of the five sequences from fatal lung infections in 1918.
Therefore, the immediate release of the sequences associated with the severe and fatal cases is warranted.