Tuesday, May 19, 2015

WHO: H5N1 Update & Risk Assessment

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The World Health Organization has posted their latest Influenza at the Human-Animal Interface, monthly risk assessment summary – current through May 1st – which adds 13 additional H5N1 cases from Egypt during the month of April, and 1 from China.

 

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Influenza at the human-animal interface


Summary and assessment as of 1 May 2015


Human infection with avian influenza A(H5) viruses

From 2003 through 1 May 2015, 840 laboratory-confirmed human cases of avian influenza A(H5N1) virus infection have been officially reported to WHO from 16 countries. Of these cases, 447 have died. 1 Since the last WHO Influenza update on 31 March 2015, 14 new laboratory-confirmed human cases of avian influenza A(H5N1) virus infection, including one fatal case, were reported to WHO from Egypt (13) and China (one).


Of the 13 human cases of influenza A(H5N1) virus infection reported from Egypt, nine had onset of disease in March and the rest had onset of disease in April. The cases were reported from eight different governorates of Egypt (see table 1 in the annex). The age range of the 13 cases is from three to 58 years, with a median of 31 years and 23% of the cases are under 10 years of age. Slightly more females than males were affected. Only one fatal case was reported and the rest have recovered and been discharged from hospital. All cases had exposure to poultry or poultry, all cases were hospitalized and all reportedly received treatment with antiviral medication.


Although all influenza viruses evolve over time, preliminary laboratory investigation has not detected major genetic changes in the limited number of viruses isolated from the patients and animals in Egypt compared to previously circulating isolates thus far, but further in depth analysis is ongoing.


Compared to the previous five months, there has been a decrease in the number of laboratory confirmed human cases of avian influenza A(H5N1) virus infection reported by Egypt since the last risk assessment. The decrease in the number of human cases over the past month is presently unclear. It is likely attributed to a mixture of factors, including fewer outbreaks in poultry, heightened public health awareness of risks and seasonal factors. The proportion of fatal cases has been consistently lower in Egypt than in other countries, especially in children.


China reported one human case of infection with an avian influenza A(H5N1) virus from Yunnan province, where two cases were detected last month. The case has recovered from his illness and was not reported to have had known exposure to poultry before illness.


Various influenza A(H5) subtypes, such as influenza A(H5N1), A(H5N2), A(H5N3), A(H5N6) and A(H5N8), have recently been detected in birds in west Africa, Asia, Europe, and North America, according to reports received by OIE. Although these influenza A(H5) viruses might have the potential to cause disease in humans, so far with the exception of human infections with influenza A(H5N1) and A(H5N6) viruses, no other subtypes of A(H5) virus infection in humans has been reported.


Overall public health risk assessment for avian influenza A(H5) viruses: The human cases reported appear to be sporadic and the virus is known to be endemic in poultry in these countries. Whenever avian influenza viruses are circulating in poultry, sporadic infections and small clusters of human cases are possible in people exposed to infected poultry or contaminated environments. Therefore additional human cases would not be unexpected.

Although an increased number of animal-to-human infections have been reported by Egypt over the past few months, these influenza A(H5) viruses do not currently appear to transmit easily among people. As such, the risk of community-level spread of these viruses remains to be low and the risk assessment remains unchanged.


Further studies are needed to understand the risk factors for human infections and the potential role of mild cases if they are occurring. More analyses on the viruses from both animals and humans need to be undertaken to better understand if any subtle changes in the transmissibility of the virus from animals to humans may be playing a role in the current situation.


A statement on the joint high-level mission to Egypt in March 2015, as well as the executive summary of the mission report, can be found at this link:


http://www.emro.who.int/egy/egypt-news/upsurge-h5n1-human-poultry-cases-may-2015.html


With the rapid spread and magnitude of avian influenza A(H5) outbreaks, notably in areas that had not experienced this disease in animals until recently, there is an increasing need for vigilance in the public health sector. Surveillance should be enhanced to detect, at the earliest stage, human infections if they occur and changes in viruses of transmissibility and pathogenicity that could have significant public health implications.

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