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Commentary
Sloppy Surveillance
Raises H1N1 Pandemic Concerns
Recombinomics
Commentary 19:31
March 2, 2010
Virus type/subtype Number of cases during current week
Influenza A 11
A (pandemic H1N1) 4
A(subtyping not performed) 4
A(H3)
A(H1) 3
A(H5)
Influenza B
Unknown 8
The above comments and data are from the ECDC week 7 report, which demonstrates the sorry state of pandemic surveillance in Europe. In the past three pandemics, a fall wave has been followed by a winter/spring wave. A winter/spring wave would begin about now, but week 7 reports are incomplete and may have entry errors. Although there were only 19 patients listed, virus was not isolated in 8. Of the 11 isolates, sub-typing was not performed on 4. On the remaining seven all were H1N1, but 3 were said to be seasonal H1N1 at a time when seasonal H1N1 has all but disappeared. Thus, it is unclear if almost half the 7 H1N1 sub-typed were actually seasonal H1N1, or were pandemic H1N1 that were mis-reported or entered in the wrong field.
Week 7 is a critical time period. The fall wave has ended and a new wave should be forming, based on the pattern of the last 3 pandemics. However, surveillance has only identified 19 patients, all of whom are likely infected with pandemic H1N1, yet pandemic H1N1 was only confirmed in four.
Moreover, 5 of 17 are said to have received the pandemic vaccine (the status of 2 was unknown), raising concerns that vaccine failure in Europe is widespread. The frequency in the 17 severe cases with reported vaccination status is similar to the vaccination rate of the entire population, suggesting that the vaccine has little effect on the emerging virus.
The number of reported cases is low, but the low number is linked to poor surveillance. Most H1N1 infected patients are either not tested or tested with a rapid test which has a sensitivity which is notoriously low and even lower for H1N1 (the CDC has reported levels as low as 10%). This low sensitivity is due in part to the ability of pandemic H1N1 to quickly move to the lungs. More serious cases would be in ICU’s where collection of appropriate lung fluids would be easier and more likely to yield H1N1 virus. However, more than half of these severe cases have not yielded virus or were not sub-typed.
Thus, at a time when surveillance should be increased, the poor surveillance yields low numbers which mitigates interpretation of the alarming numbers which suggest the frequency of vaccinated patients in the H1N1 severe group is similar to the frequency in the population as a whole.
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