Tuesday, April 14, 2015

WHO H5N1 Risk Assessment (As of 3/31/15)

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# 9935

 

Yesterday a (broken) link went up for the World Health Organization’s latest H5N1 summary, along with a new Cumulative number of confirmed human cases of avian influenza A(H5N1) chart.   This morning that link has been fixed, and we get a snapshot of the H5N1 situation – as reported by the Egyptian MOH to WHO – as of two weeks ago.

 

Before we jump into this report, a brief note regarding case totals:  They are all over the place.

 

Not only are the actual number of cases likely under reported in Egypt, various agencies have provided different tallies.  Last week, in WHO H5N1 Update For Egypt – Thru March 31st, we saw a report from the WHO’s EMRO division (see chart below) that listed 125 cases, and 33 deaths in Egypt as of the end of March.

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But yesterday’s WHO cumulative Case chart thru March 31st listed 119 cases, and 30 deaths.

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It is also worth noting that yesterday’s chart increased Egypt’s 2014 tally to 37 cases and 14 deaths, up from 31 cases and 10 deaths last reported on 3/03/15.   So I suspect that some cases previously listed occurring in 2015 cases – after reviewing their onset dates - have been shifted back into 2014.

 

The point being that the case data coming out of Egypt is constantly changing and subject to revision. 

 

Meaning  we should avoid putting too much emphasis on `exact numbers’ for any given cut off date (which are almost certainly wrong) , and look instead at the trends.   Which unfortunately continue to rise.

First some excerpts from the latest WHO Risk Assessment, after which I’ll return with a bit more.



 

         Summary and assessment as of 31 March 2015

Human infection with avian influenza A(H5) viruses

From 2003 through 31 March 2015, 826 laboratory-confirmed human cases of avian influenza A(H5N1) virus infection have been officially reported to WHO from 16 countries. Of these cases, 440 have died.


Since the last WHO Influenza update on 3 March 2015, 42 new laboratory-confirmed human cases of avian influenza A(H5N1) virus infection, including 11 fatal cases, were reported to WHO from Egypt (37), China (three) and Indonesia (two).


Of the 37 human cases of influenza A(H5N1) virus infection reported from Egypt, 14 had onset of disease in February and the rest had onset of disease in March. The cases were reported from 14 different governorates of Egypt (see table 1 in the annex). The age range of the 37 cases is from one to 77 years, with a median of 24 years and 38% of the cases are under 10 years of age. Almost twice as many females compared to males were affected. Eight of the 37 cases (22%) died and all eight fatal cases were in patients 10 years of age and older. All but one case had exposure to poultry or poultry markets and the exposure history of the one case is still under investigation. All cases were hospitalized and all reportedly received treatment with antiviral medication. Contacts of the cases were followed for 14 days and there have not been reports of cases in any contacts of confirmed cases. The newly-reported cases included one cluster of two confirmed cases in a mother and son from Sharkia governorate. The two cases had onset of illness on the same day and both had exposure to backyard poultry, suggesting common exposure.


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. 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 compared to previously circulating isolates thus far, but further in depth analysis is ongoing. A new candidate vaccine virus was proposed to better protect against the current circulating H5 clade 2.2.1. viruses (a group which all the recent influenza A( H5N1) virus isolates from Egypt belong to).

For the fourth consecutive month since December 2014, the number of laboratory-confirmed human cases of avian influenza A(H5N1) virus infection in Egypt with disease onsets in each month are the highest numbers reported by any country in a single month. The characteristics of the affected population remain essentially unchanged from previous years in Egypt, with females more commonly affected than males and about one third of the cases occurring in children under ten years of age. The proportion of fatal cases has been consistently lower in Egypt than in other countries, especially in children, although the case fatality rate could change as many cases remain hospitalized.


The increase in the number of human cases is likely attributed to a mixture of factors, including increased circulation of influenza A(H5N1) viruses in poultry, an increasing number of small poultry farms and household flocks, lower public health awareness of risks and seasonal factors such as closer proximity to poultry because of cold weather and possible longer survival of the viruses in the environment.


China reported three human cases of infection with an avian influenza A(H5N1) virus from two provinces. Two cases were reported to have had exposure to live poultry. One of the human cases was a fatal case while the other two cases were still under treatment at the time they were reported. Indonesia reported two fatal human cases of infection with an avian influenza A(H5N1) virus, in a father and a son from Banten province. The investigation surrounding these two cases indicates that they may have had indirect or direct contact with birds near their residence or in another district they visited prior to their onsets of illnesses. Both cases developed severe disease and were hospitalized but passed away. The last human case of infection with an avian influenza A(H5N1) virus in Indonesia was reported in June 2014.


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 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 no human cases of infection have been reported, with exception of the human infections with influenza A(H5N1) viruses and the three human infections with influenza A(H5N6) virus detected in China since 2014.

Overall public health risk assessment for avian influenza A(H5) viruses: The cases reported from these three countries appear to be sporadic cases and the virus is known to be circulating endemically 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 the additional sporadic 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. Although 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. Further analyses on virus isolates from the animal sector and human cases need to be undertaken to better understand if changes in the transmissibility of the virus from animals to humans may be playing a role in the current situation.

(Continue . . . )

 

While we’ve not seen any evidence of increased or efficient human-to-human transmission of the H5N1 virus in Egypt, it is worrisome that this outbreak has now gone on for five full months, and that in excess of 160 people have been infected.

 

A couple of weeks ago, in Eurosurveillance: Emergence Of A Novel Cluster of H5N1 Clade 2.2.1.2, we looked at a study that found a new strain of H5N1 has emerged in Egypt and has rapidly become the predominant strain in poultry, and that suggested that genetic changes in this strain may be making it more easily transmitted from birds to humans.

 

Egypt has also reported heavy rates of poultry infections this winter – even among vaccinated flocks (see Egypt H5N1: Poultry Losses Climbing, Prices Up 25% - which calls into question the effectiveness of the vaccines currently being used.

 

Whether due to genetic changes to the virus, or simply due to a greater prevalence in Egyptian poultry, this year’s outbreak has reached historic, and unprecedented levels. Heightening concerns that the longer this goes on, the more opportunities the H5N1 virus will have to figure out how to thrive and prosper in a human host.

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