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CDC Update On The Pennsylvania Swine Flu Cases

 

 


# 5821

 

 

The CDC has released a couple of new updates to the big story we’ve been following for a week – the detection of several novel H3N2 swine flu infections among 4 children living in Indiana (1) and Pennsylvania (3).

 

Earlier stories include:

 

Pennsylvania DOH: Updated FAQ On The Novel Swine Flu Cluster
Pennsylvania Reports 2 More Novel Flu Cases
MMWR: Swine-Origin Influenza A (H3N2) Virus Infection in Two Children

 

The epidemiological investigation is ongoing, and there remain many unanswered questions regarding the source, pathogenicity, and transmissibility of this virus. 

 

Alas, good science takes time. 

 

While the CDC continues to investigate, thus far the good news, according to Lyn Finelli - Chief Outbreak Investigator for CDC’s  Influenza Division – is that:

 

“. . . it does not look like there is current spread in the community and so far, illness associated with these viruses has not been especially severe. Two of the patients are fully recovered and the third is recovering.”

 

 

The CDC continues to update this situation on their HAVE YOU HEARD? webpage. You’ll find excerpts from a much longer entry below. 

 

Follow the link to read it in its entirety.

 

 

Number of Swine Origin H3 Infections in Pennsylvania Rises to Three

September 6, 2011 -- CDC laboratory testing has confirmed two additional cases of human infection with swine origin influenza A (H3) viruses in children in Pennsylvania. These additional two cases bring the total number of confirmed cases of human infection with swine origin influenza A (H3) viruses from the Pennsylvania investigation to three. According to the Pennsylvania Department of Health, all three of the children confirmed with swine origin influenza A (H3) influenza infection reportedly attended the Washington County Agricultural Fair the week of August 13-20, 2011, where swine were exhibited.

 

The first case of human infection with swine origin influenza A (H3) in Pennsylvania was reported in an MMWR early release issued on Friday, September 2, 2011 and occurred in a girl younger than 5 years. The two cases confirmed over the weekend also occurred in girls, both younger than 10 years. All three of the patients were in the area where swine were exhibited and one had direct contact with swine.

 

Like humans, pigs can become infected with and spread their own influenza viruses. The symptoms of swine flu in pigs are very similar to the symptoms humans get from human seasonal flu illness and can include coughing, lack of appetite, runny nose and lethargy. Not only do pigs become infected and spread swine influenza viruses, but they can be infected with both human and avian influenza viruses. Though rare, humans also can be infected with swine influenza viruses.

 

“It′s pretty rare to see human infections with swine flu viruses. CDC gets reports of about 5 cases of human infections with swine flu viruses each year,” says Lyn Finelli, Chief Outbreak Investigator for CDC′s Influenza Division. “Most of the time, these cases occur after close contact with pigs and seldom spread onward from the first person infected.” There have been rare cases where human-to-human transmission may have occurred, most recently in Indiana in a case also reported in the September 2, 2011 MMWR early release. “The hallmark of influenza viruses is their ability to change,” cautions Mike Shaw, the Influenza Division′s Associate Director for Laboratory Science. “That is why we watch these types of situations closely, to make sure that the virus hasn′t changed to allow efficient and sustained human-to-human transmission.”

(Continue . . . )

 

 

A second embedded link provides us with some background on the genetics of this new virus, showing how it is the product of reassortment, with 7 gene segments from the H3N2 swine flu virus and 1 gene segment (M) from the 2009 H1N1 virus.

 

Number of Swine Origin H3 Infections in Pennsylvania Rises to Three [508 Image Compliance Text]

image

The above graphic depicts how the human cases of swine-origin H3N2 influenza virus reported in Indiana and Pennsylvania resulted from the reassortment of two different influenza viruses. The image on this page shows three influenza viruses placed side by side, with eight color-coded RNA segments inside of each virus. Note: All influenza viruses contain 8 RNA segments. These RNA segments are labeled HA (hemagglutinin), NA (neuraminidase), PB1, PB2, PA, NP, M and NS.

 

The virus in the center of the picture represents the human cases of swine-origin H3N2 influenza in Indiana and Pennsylvania. Seven of these viruses’ eight RNA segments are derived from influenza viruses that commonly circulate in pigs. The virus on the left of the diagram, labeled “1998-2011 swine H3N2 triple reassortant viruses,” represents these swine influenza viruses. These swine viruses are called triple reassortant viruses because they contain genetic material from humans, pigs and birds.

(Continue . . .)

 

Anytime a novel influenza virus jumps species and demonstrates the ability to infect humans, it is a matter of both scientific curiosity and concern.

 

We’ve seen a number of novel flu viruses emerge over the past few years, and with the notable exception of the 2009 H1N1 pandemic virus, all have turned out to transmit poorly in humans.

 

Given the limits of testing and surveillance, it is likely that limited transmission of novel flu viruses to humans is far more common than we know.

 

The concern is that another novel virus could evolve that is both pathogenic and easily transmissible among humans.

 

Which is why epidemiologists take investigations of novel swine flu infections like these so seriously.

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reassortment
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