Some of the nation's emergency departments are noting increases in flu-like illness cases that appear to be pandemic H1N1, and colleges are reporting the first increase in flu-like illness since the end of November, but it's not clear if these are early signs of a third pandemic flu wave.
The American College of Emergency Physicians (ACEP) said today in a Twitter post that some of its members were anecdotally reporting a new wave of pandemic H1N1 patients coming to emergency departments and asked if other physicians were seeing similar patterns.
Carl Schultz, MD, professor of emergency medicine at the University of California at Irvine, told CIDRAP News that the increase in the number of influenza-like illnesses appears to be real, but he cautioned that many of the cases have not been confirmed as the pandemic H1N1 strain, because many departments stopped specifically testing for it because of low flu activity. Schultz chairs ACEP's disaster preparedness and response committee.
The above comments provide additional data that a third wave in the United States has begun. Reports on flu at universities has increased 52% over last week, which is supported by anecdotal reports from emergency room physicians. The largest number of new student cases was again in North Carolina.
These developments parallel the start of the fall wave. The initial cases were in region 4 and this area has had the highest percent of samples being H1N1 positive. Similarly, state reports showed recent increases in North Carolina and Alabama, while earlier reports describe more severe cases in hospitals in Tennessee and North Carolina.
The initial reports from region 4 may signal the emergence of a more evolved H1N1 since the time between the current outbreak and cases reported in the fall would be greatest. A recent report on Allegheny County, location of metropolitan Pittsburgh found H1N1 antibody in 45% of patients age 10-17. If this population is again being targeted, it is likely that there are re-infections and the new virus has escaped the immune response generated against the fall wave.
Recently released sequences from low reactors indicated that a single nucleotide change could move a sequence into the low reactor category, and recombination was creating new sequences with multiple low reactor polymorphisms, which if additive would lead to widespread vaccine failure and frequent infections of patients infected last year.
Sequence data on new cases, including severe and fatal cases would be useful, as would H1N1 history of these new patients.
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