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Paradigm Shift Intervention Monitoring
Of the 16 influenza specimens sutyped
(sic) at the state lab, 5 (31%) were the 2009 A/H1N1, 2 (12%) A/H3, 7
(44%) were influenza type A and 2 (13%) were unsutypeable (sic)
influenza type A.
The above comments are from the week 4 report from Pennsylvania (PA) and indicate H1N1 has become dominant in the state. The dominance appears to be widespread. Initially, most of the reported H1N1 was in eastern PA. An alert was issued for Lehigh County, where two previously healthy young adults died from H1N1. That was followed by an alert for Montgomery County, where 3 young patients died over a short period at the end of 2010 / beginning of 2011. However, in the latest report, the largest number of reported H1N1 cases is in Allegheny County (Pittsburgh) in western PA.
Moreover, the most affected age group is now 25-49, the prime target for H1N1. The CDC has released three sets of H1N1 sequences from PA and all three were identical. The demographic data matched the outbreak in Lehigh County and the November sequences had S186P. Sequences from other states indicated H1N1 was largely the two sub-clades (with S186P or S188T) dominant in England in November, when a serious outbreak began. The December UK sequences were exclusively the S188T sub-clade, and it is likely that similar dominance is in the United States, although no December / January sequences have been released by the CDC,
The S188T sub-clade in England produced a high rate of severe and fatal cases, which filled ICU beds and put a severe strain on available ECMO machines. The data in PA suggests that a similar scenario will follow in the US. In the UK, H1N1 was the dominant subtype. H3N2 was rare and increases in influenza B have begun recently. In PA, H3N2 was dominant in the fall of 2010, but now H1N1 is on the rise. It is also the dominant serotype in adjacent New Jersey, where the P&I deaths have spiked to 8.53%. A similar trend is likely throughout the US.
In PA, the number of deaths is up to 21, which is almost certainly the highest in the country. Hospitalizations also began to spike in early 2011. The week 1 report had 70 cases, up from 23 reported for week 52 and 11 in week 51. PA did not issue a week 2 report, and hospitalization numbers for week 3 and 4 have not been reported, although they are likely to be markedly higher because the number of reported deaths has almost doubled from 11 in week 1 to 21 by week 4.
Thus, it is likely that the number of severe and fatal H1N1 cases will spike higher in the US in the coming weeks. Release of H1N1 sequences from December and January would be useful.