Jim wrote:
I've been pouring over the isolates data from State websites since the beginning of the year. I have noticed that in some states, mostly on the east coast, a certain percentage of samples have been identified as pH1N1 and that it has been co-circulating with Flu B and H3N2 since early in the season. In these states, severe cases and deaths have been low. Even in North Carolina, where they had a number of deaths (an unusually high number of pediatric deaths), many of those deaths were attributed to Flu B and H3N2. Some deaths were attributed to pH1N1 and, based on the isolates data, it was the dominant strain; however, they have experienced the classic peak and flu season appears to be over there, just like in Mexico. I suspect that the strain circulating in NC is closer to A/California/7/2009.
Also, although Ontario had a bad flu season (with over 175 fatalities), when you look at the age range of fatalities, it has a seasonal flu signature - high on the ends and low in the middle. Then, if you look at the isolates data, Ontario has had very little pH1N1.
There have been some anomalies, though. We've been discussing the outbreak in the Pittsburg area (and Pennsylvania still hasn't posted Week 12 results). There have also been 20 fatalities each in LA and San Diego Counties. Furthermore, Texas has reported the highest number of pediatric deaths this season (13), which is nearly one-third the total they experienced in the 2009-10 season (47). From April 2009 through August 2010 they had, by far, the largest number of pediatric deaths per capita (54 deaths, or 2.1 deaths per million); only second behind California (57) in the actual number of pediatric deaths. So, based solely on the number of pediatric deaths and the fact that most (9 deaths) occurred recently (in Weeks 7 through 10), we should suspect that something is up in Texas.
Yes, I think it is a bit trickier to see activity in the US because of other viruses, including the more standard pH1N1.
I think the new sequences will be quite obvious however, which is why I am very suspicious of the delay in release by the CDC. They usually release H1N1, H3N2, and influenza B in three sets within a day or two of each other. H3N2 and influenza B were released over a week ago, but no H1N1.
Rumor has it that sequences from Mexico will be released next week, and the problems will be quite clear.
Until the sequences come out, I think most of the analysis will be indirect, as you have done above.