H3N2 influenza virions –CDC PHIL
# 6019
The recent detection of a handful of novel swine-origin influenza infections across four US states is a reminder that influenza viruses continue to mix and match and evolve, and that new (and potentially dangerous strains) can appear with little warning.
While the CDC states that these S-OIV trH3N2 viruses have yet to demonstrate an ability to spread efficiently among the human population - and therefore don’t currently pose a major public health threat - the concern is that over time they could obtain that capability.
So agencies like the CDC, the ECDC, the World Health Organization, and others are encouraging a heightened awareness and vigilance in the testing and reporting on any unusual (or un-subtypable) flu cases.
The following notice was posted on the WHO’s influenza page late yesterday (hat tip AlohaOR on the Flu Wiki).
WHO Comment on the importance of global monitoring of variant influenza viruses
19 December 2011
Human infections with variant influenza viruses
Recently, several human infections with variant influenza viruses currently thought to be circulating in swine populations have been reported. To date, epidemiological investigations have not revealed any onward transmission of these viruses outside of small clusters. Avian influenza H5N1 viruses also continue to cause infections in humans exposed to infected birds and contaminated environments especially in countries where the virus is considered endemic in poultry. Thus far, transmission of these variant viruses from animals to humans has only resulted in sporadic human cases or small clusters among close contacts, with no evidence of community level spread. These sporadic human cases and small clusters of human infection with variant influenza viruses are expected and are not considered unusual, and do not change WHO’s current assessment of pandemic risk.
However, because influenza viruses are unpredictable, they have the possibility to change and become more transmissible among humans as shown by the emergence of the influenza pandemic H1N1 virus in 2009. For this reason, continued monitoring of the occurrence of human infections with these viruses and characterization of the viruses themselves are critically important to assess their pandemic potential.
WHO reminds Member countries that it is an obligation under the International Health Regulations (IHR) to report to WHO all human cases of infection with influenza viruses that are not currently circulating seasonally in human populations (http://www.who.int/ihr/survellance_response/case_definitions/en/index.html), and to conduct epidemiological investigations around each case to identify or rule out any onward human-to-human spread which could indicate emergence of a more transmissible virus. WHO will continue to share information about variant influenza viruses with the international public health community in accordance with WHO's obligations under the IHR.
WHO also strongly recommends that all un-subtypable influenza A specimens should be immediately sent for diagnosis and further characterization to specialized laboratories or one of the six WHO Collaborating Centres for Reference & Research on Influenza (http://www.who.int/influenza/resources/documents/diagnostic_recommendations/en/index.html),
This is important for early identification of emerging viruses with the potential to threaten global public health.
It isn’t just the S-OIV trH3N2 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 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 seriously, and are encouraging enhanced global surveillance to track their evolution and spread.
It is too soon to know whether any of these new flu strains will take hold in the human population.
As I wrote in Pseudo Pandemics And Viral Interlopers it is certainly 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.
Update: I noted shortly after posting this blog that Helen Branswell of the Canadian Press has an article on this WHO release as well.
Keep an eye out for new flu viruses: WHO
12/19/2011 | Helen Branswell, The Canadian Press
