Credit CDC – 9/7/12 Update
# 6541
The CDC has updated their case counts of human infections with the swine H3N2v virus, indicating another 8 cases have been confirmed, along with 1 additional hospitalization.
This is the second week in a row with a relatively low increase in the number of new confirmed infections, although it should be mentioned that there remain a number of `suspected or probable cases’ that are not in today’s tally.
Pennsylvania, for instance, is reporting 11 confirmed cases, but lists another 30 `probable’ on their website this morning.
And it is likely that many mild, or sub-clinical cases simply go untested.
The CDC’s Assessment of the situation reads:
CDC Assessment
It's possible that sporadic infections and even localized outbreaks among people with this virus will continue to occur. While there is no evidence at this time that sustained human-to-human transmission is occurring, all influenza viruses have the capacity to change and it's possible that this virus may become widespread. So far, the severity of illnesses associated with this virus in people has been similar to the severity of illnesses associated with seasonal flu virus infections. Limited serologic studies indicate that adults may have some pre-existing immunity to this virus while children do not. CDC is closely monitoring human infections with all novel influenza viruses, including H3N2v viruses, and will provide more information as it becomes available.
Even if you consider the gaps in surveillance, and likely under-reporting of infections from this virus, H3N2v obviously isn’t spreading anything like the H1N1pdm09 virus did during its debut in the spring of 2009.
To put this into perspective, we are roughly 7 weeks since the first clusters began to appear in the Midwest (July 12th, 2012), and we are (just barely) below 300 confirmed cases across 10 states.
The following blast from the past shows the number (and wide geographic spread) of 2009 H1N1 virus detections being reported to the World Health Organization in early June 2009, roughly 7 weeks after it was first detected.
Influenza A(H1N1) - update 45
8 June 2009 -- As of 06:00 GMT, 8 June 2009, 73 countries have officially reported 25,288 cases of influenza A(H1N1) infection, including 139 deaths.
There were, by the way, plenty of gaps in testing and surveillance for the H1N1 virus back in 2009 as well. The numbers reported above are generally considered to be an undercount.
While the H3N2v virus may very well develop `legs’ over time - and eventually pose a larger public health threat - right now it obviously isn’t spreading anything like its H1N1pdm cousin did.
Today’s FluView Report has a summary of the novel H3N2v activity and the three H1N2v cases reported last week (see Minnesota Reports Swine H1N2v Flu)
2011-2012 Influenza Season Week 35 ending September 1, 2012
All data are preliminary and may change as more reports are received.
Novel Influenza A Virus:
From July 12 through September 6, 2012, a total of 296 infections with influenza A (H3N2) variant (H3N2v) viruses have been reported from ten states. This is an increase of 8 over last week’s report. Cumulative totals by state since July 15 are: Hawaii [1], Illinois [4], Indiana [138], Maryland [12], Michigan [5], Minnesota [2], Ohio [102], Pennsylvania [11], West Virginia [3], and Wisconsin [18]. Sixteen H3N2v-associated hospitalizations and one H3N2v-associated death have been reported. The vast majority of cases have occurred after prolonged swine exposure, though instances of likely human-to-human transmission have been identified. At this time no ongoing human-to-human transmission has been identified.
<SNIP>
As a result of enhanced surveillance activities for H3N2v, three infections with influenza A (H1N2) variant (H1N2v) virus have been detected in Minnesota in patients who became ill after contact with swine. One patient was hospitalized, but all have recovered from their illness. Confirmatory testing at CDC identified H1N2v with the matrix gene from the 2009 H1N1 influenza virus in specimens collected from all three patients. Although cases of H1N2v have been detected previously, the current cases mark the first reports of H1N2v with the matrix gene from the 2009 H1N1 virus.
Otherwise, surveillance of flu activity around the country shows very little activity, despite the scattered reports of H3N2v in the Midwest.
And the 122 Cities Pneumonia & Influenza mortality surveillance continues to indicate deaths are running well below the seasonally adjusted epidemic level.
Pneumonia and Influenza (P&I) Mortality Surveillance:
During week 35, 5.6% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was below the epidemic threshold of 6.5% for week 35.
With cooler weather on the way, another 6 to 8 weeks of state and county fairs (mostly in the south), and schools now going back into session, we’ll be watching closely to see if this two-week decline in new cases is a temporary lull, or a sustained trend.
Stay tuned.
