Thursday, July 16, 2015

WHO WER: Human Cases Of Influenza At The Human-Animal Interface, Jan 2014-Apr 2015

WHO Xray
Credit WHO



Although it has been largely overshadowed by other emerging  global public health concerns (notably Ebola & MERS) in the mainstream press,  2014 and the spring of 2015 have seen a major uptick in the number of novel flu (H5N1, H7N9, H5N6, H9N2, etc.) human infections around the globe.  


Based on WHO Data


Outside of international public health circles, and the denizens of Flublogia, little notice has been paid to this trend, largely because the two largest contributors to these totals – China and Egypt – have been less than eager to publicly acknowledge their cases.  Their notifications to the WHO have often been delayed and sparse in details.

By way of comparison, during the middle of the last decade – at the height of avian flu concerns -  the largest number of H5N1 cases reported in a single year was 115 (in 2006), and other novel flu subtypes barely made a blip on the radar.  

Of course, the number of reported cases and the actual incidence of any disease often differ greatly. In some countries surveillance, testing, and reporting may improve (or degrade) over time, and in many parts of the world no surveillance is done at all.


Still a five-fold increase in reported cases, and a marked jump in the number of novel flu subtypes, is worthy of our attention.


This week the World Health Organization’s Weekly Epidemiological Record (WER) has a long, data rich review of novel flu infections reported during 2014 and into the spring of 2015.  This report is too long, and the charts are too large, to adequately excerpt, and most will want to download it for future reference anyway.

Therefore I’ve just reproduced the discussion portion, click the link below to download the complete report.


Human cases of influenza at the human-animal interface, January 2014-April 2015

Aspen Hammond,a Kaat Vandemaele,a Julia Fitznera



As in previous years, human cases of infection with non-seasonal influenza viruses remain rare with sporadic cases occurring following exposure to infected poultry or environments contaminated with infectious viruses. There has been no evidence of sustained human-to-human transmission of any of these nonseasonal influenza viruses. As long as these viruses continue to circulate in animal populations and people are exposed to them, further sporadic human infections are likely.

Several important events have occurred since early 2014 with regard to non-seasonal influenza viruses. Firstly, Egypt suffered a dramatic increase in reported human infections with influenza A(H5N1) viruses from December 2014 through March 2015. The epidemiological characteristics of the human cases remained essentially unchanged from previous years and no significant genetic changes have yet been detected that could explain a change in virus transmissibility.

More than a third of the human cases reported from Egypt were in children aged <10 years and the CFR remained lower compared to human cases reported from other countries. Differences in CFR between countries may depend on host factors (genetic susceptibility), the genetic diversity of the infecting viruses, access to health care and health seeking behaviour. The majority of the human cases which have occurred in Egypt also received prompt treatment and hospitalization.

The first human cases of infection with influenza A(H5N6) also occurred in 2014. This virus is a genetic reassortant derived from influenza A(H5N1) viruses and other avian influenza viruses. It has now been detected in poultry in several countries in Asia. This virus falls in the HA H5 genetic clade which includes other influenza A(H5) reassortants, such as A(H5N1), A(H5N2), and A(H5N8), that have spread rapidly from Asia to bird populations in Europe and North America. While no human infections with these viruses have been reported to date, it is possible that these influenza A(H5) viruses could infect humans who are in contact with infected birds.

In addition to the human infections with the various A(H5) viruses described above, influenza A(H7N9) viruses caused a third wave of human infections in China, and it is likely that these viruses have become established in the local poultry populations.

The continuous evolution of influenza viruses, unprecedented reassortment events, and detections of nonseasonal viruses in humans emphasizes the importance of continued surveillance at the human-animal interface. It is critical that health-are providers are alert to the possibility of human cases of infections with nonseasonal influenza viruses and suspicious of any clusters of respiratory illnesses especially in at-risk individuals.

Detailed epidemiological and clinical investigations are important for learning more about the risk factors for infection as well as the clinical course of infections in humans. Virus characterization, in particular antigenic characterization and full-genome sequencing, is essential to assess the pandemic potential of these viruses, for which close collaboration between animal health and public health partners is indispensable.

WHO continues to stress the importance of global monitoring of influenza viruses and recommends that all Member States strengthen their routine influenza surveillance. All human infections with an influenza A virus that has the potential to cause a pandemic should be reported to WHO in accordance with the IHR (2005).

1 comment:

Giga Gerard said...

The numbers are staggering. The world's average stock of chickens is about 20 billion.