Tuesday, January 13, 2015

WHO H5N1 Update & Risk Assessment




# 9567


The World Health Organization has published their latest Influenza at the human-animal interface report, dated January 6th, that lists 18 recent H5N1 cases in Egypt, along with an H5N6 case in China.   All of these cases have previously been reported by their respective Ministries of Health, and in this blog.

The past couple of months has seen a major uptick in H5N1 cases in Egypt, and  today’s report provides some details on a family cluster (2 siblings confirmed, with 1 (deceased) parent probable) of H5N1 in Giza. 

While clusters are always a concern, they do not necessarily indicate human-to-human transmission as all of these cases could have shared an environmental exposure.  As the report indicates, the investigation is ongoing.

Human infection with avian influenza A(H5N1) viruses

From 2003 through 6 January 2015, 694 laboratory-confirmed human cases of avian influenza A(H5N1) virus infection have been officially reported to WHO from 16 countries. Of these cases, 402 have died. Since the last WHO Influenza update on 4 December 2014, 18 new laboratory-confirmed human cases of avian influenza A(H5N1) virus infection, including four fatal cases, were reported to WHO from Egypt. Two cases had onset of disease in November 2014, the others had onset of disease in December 2014. The cases were reported from eight different governorates of Egypt (see table 1).

There was one cluster reported which included two confirmed cases in siblings from Giza governorate and one probable case in the siblings' mother who died from acute respiratory syndrome but was not tested for the avian influenza A(H5N1) virus. The investigation of this cluster is ongoing.

All cases had exposure to sick or dead poultry. Identification of such sporadic human cases or small clusters are not unexpected as avian influenza A(H5N1) viruses are known to be circulating in poultry in the country.

Currently, there are reports of an increased number of outbreaks and detections of influenza A(H5N1) viruses in poultry in Egypt compared to previous months and compared to this month in previous years. This is the highest number of laboratory-confirmed human cases of avian influenza A(H5N1) virus infection reported by Egypt in a single month.

Although all influenza viruses evolve over time, preliminary laboratory investigation has not detected major genetic changes in the viruses isolated from the patients or animals compared to previously circulating isolates. The increase in reported human cases is likely a consequence of several factors. These includes increased circulation of influenza A(H5N1) viruses in poultry, lower public health awareness of risks in middle and upper Egypt and seasonal factors such as closer proximity to poultry and longer survival of the viruses in the environment because of cold. Epidemiological and virological investigation in humans and animals is ongoing.

Overall public health risk assessment for avian influenza A(H5N1) viruses: Whenever avian influenza viruses are circulating in poultry, sporadic infections or small clusters of human cases are possible in people exposed to infected poultry or contaminated environments, especially in households. Human infections remain rare and these influenza A(H5N1) viruses do not currently appear to transmit easily among people. As such, the risk of community-level spread of these viruses remains low.


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