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MMWR: H3N2v Transmission and Guidelines

 

 

# 6033

 

 

Late this afternoon the CDC published an early release to the MMWR titled Update: Influenza A (H3N2)v Transmission and Guidelines — Five States, 2011 focused on the novel H3N2v flu that has captured our attention since August.

 

Earlier today (see CDC: Variant Influenza Strains) we saw a chart giving the geographic spread of these detections.

 

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States reporting the new A(H3N2)v virus since July. – Source CDC

 

We are also reminded that:

 

It's possible that sporadic infections and even localized outbreaks among people with this virus will continue to occur.

While there is no evidence 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.

 

 

Today’s MMWR provides details on three recent cases in Indiana and West Virginia, along with background information on the virus and its spread.  You can read the entire release at the link below:

 

Update: Influenza A (H3N2)v Transmission and Guidelines — Five States, 2011

Early Release

December 23, 2011 / 60(Early Release);1-4

 

 

The authors provide the following summary:

 

 

What is already known on this topic?

During August–December 2011, a total of 12 human infections with influenza A (H3N2)v viruses were identified in the United States (two from Indiana, three from Iowa, two from Maine, three from Pennsylvania, and two from West Virginia).

What is added by this report?

This report provides the new nomenclature for the virus and describes three cases, one in an adult with occupational exposure and two in children involving limited human-to-human transmission in a day care setting. It also provides an overview of the U.S. Department of Agriculture's swine influenza virus (SIV) surveillance program along with data on influenza A (H3N2) viruses in swine. Out of approximately 150 SIV isolates that have undergone sequencing of three genes (hemagglutinin, matrix, and neuraminidase gene segments), 30 have been identified as A(H3N2) viruses; eight of those 30 have the M gene from the influenza A (H1N1)pdm09 virus.

What are the implications for public health practice?

Nonhuman influenza virus infections rarely result in human-to-human transmission, but the implications of sustained ongoing transmission between humans is potentially severe; therefore, prompt and thorough identification and investigation of sporadic human infections with novel influenza viruses are needed to reduce the risk for sustained transmission.

 

 

 

The CDC has also posted a new report on their Have you heard? website, with useful details and background on these H3N2v viruses.

 

CDC Confirms Detection of A Different Influenza A Variant Virus


H1N1v virus

December 23, 2011 -- An influenza A (H1N1) virus that is known to circulate in U.S. swine but not humans has been detected in an adult in the state of Wisconsin. The patient reported occupational contact with swine prior to illness onset. No human-to-human transmission with this virus has been identified. CDC laboratory testing has confirmed that this is a new reassortant influenza A H1N1 virus as it has acquired the matrix [M] gene from the 2009 H1N1 pandemic virus. Laboratory testing shows that the virus is susceptible to the influenza antiviral medications, oseltamivir and zanamivir. Surveillance for additional human cases in the area has been enhanced. Providers are being asked to collect specimens for influenza virus testing from any patient presenting with influenza-like illness.

(Continue . . . )

 

 

 

Of course, it isn’t just the H3N2v virus that concerns health authorities. The H5N1 bird flu virus, avian H9N2, along with some H7 and H11 strains of avian influenza have all demonstrated some ability to infect humans. 

 

While none have as yet managed to adapt well enough to human physiology to spread efficiently, the CDC and public health officials are obviously taking these novel virus detections very seriously, and are encouraging enhanced global surveillance to track their evolution and spread.

 

It is too soon to know whether any of these flu strains will take hold in the human population. 

 

As I wrote in Pseudo Pandemics And Viral Interlopers it is possible for new strains of influenza to appear and circulate among humans, without sparking a pandemic.

 

 

For now, we are in a watchful waiting mode; looking for signs that one of these novel viruses is getting better adapted to human physiology.

 

In the meantime, maintaining good flu hygiene this winter (washing/sanitizing your hands, covering coughs & sneezes, staying home when sick), and getting your seasonal flu shot, remain the best strategies to avoid getting sick during this flu season.

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