Monday, January 16, 2017

The Challenge Of Avian Flu Surveillance In Sub-Saharan Africa

HPAI Reports 2016 - Credit OIE


Over the weekend we've seen media reports (see AP's Uganda confirms Avian flu in wild terns, domestic birds) of a mass die off of wild birds on Lake Victoria (reportedly of white-winged black terns) as well as in a handful domestic ducks and chickens, which have tested positive for an, as yet, unannounced strain of bird flu.

While Nigeria and a handful of other West African nations reported outbreaks of H5N1 during the middle of the last decade, bird flu reports from Sub-Saharan Africa dried up by the middle of 2008. The virus has remained endemic in Egypt, but in late 2014 - after an absence of nearly 7 years - we began to see reports emerge from West Africa again.

In April of 2015, in EID Journal: H5N1 In Nigerian Poultry – 2015, we saw the first reports that it was clade  of H5N1 - previously detected in  China - that had emerged, not the old clades  2.2 and 2.2.1 which had previously circulated in the region.

Since then - see the OIE map above - western Africa has remained a hotbed of H5N1 activity, although no human infections have been reported (note : H5N1 is endemic in Egypt, and so they are no longer reported to the OIE). 

Exactly why hundreds of Egyptians (and some seroprevalence studies suggest that is a major under count) have been infected with H5N1, yet only 2 human infections have been reported in all of Sub-Saharan Africa, is unknown.

One strong possibility: avian flu surveillance in across Africa is often - to put it kindly - suboptimal.  Our assumption is that it is far more widespread than is officially reported.

A good example came last March in Libya's Under Reported Burden Of H5N1 (FAO Workshop), where we saw an FAO report which cited `at least 4 deaths' due to H5N1 in Libya beginning in December of 2014, and more than 100 suspected or confirmed poultry outbreaks.

Yet `officially',  Libya has never reported a human H5N1 infection to WHO and their only OIE report in 2015 listed 12 chickens affected by H5N1.

West Africa, in particular, has reported a great many outbreaks in poultry, but outside of Egypt, only two human infections have ever been confirmed by the WHO in Africa; one in Djibouti in 2006, and one the following year in Nigeria.

There were three other suspected Nigerian cases at the time - including the mother of the confirmed case in Lagos – but testing was delayed, and `inconclusive’.

The sad reality is, roughly six thousand people die each and every day in Africa, from all manner of diseases. AIDS, lassa fever, malaria, pneumonia, water borne illnesses, and TB; just to name a few. In many (probably most) cases, these people aren't afforded access to modern medical care, and even if they are, they are almost never tested for `novel' flu strains.

A lack of reported cases in areas where no testing is done, doesn't really tell us much.

These surveillance gaps are no secret. In the summer of 2015 , in FAO: Concerns Rising Over Spread Of Avian Flu In Africa and again in October of that year, in WHO Scales Up Influenza Surveillance In Africa, we looked at growing concerns over the recent spread of highly pathogenic avian flu in Africa and the very limited surveillance and reporting from the region.

Again, last summer, in The FAO Calls For Increased Vigilance On H5N1 In Africa,  we looked at concerns over the lack of surveillance in Sub-Saharan Africa.

If you look at a map of the migratory bird flyways (see above), you see that West Africa sits at the southern intersection of no fewer than three major migratory flyways. Routes that begin in the northern climes of Russia, Mongolia, and China where H5N1, H5N8, H5N6 and H7N9 are  known to circulate in wild birds – and that cross both Europe and the Middle East.

The recent breakout of  both H5N8 in Europe and H5N6 in Asia illustrate how quickly these viruses can expand their geographic range, carried in by migratory birds. 
The unidentified virus behind the bird die off in Uganda is most likely HPAI H5 (and that could include H5N1, H5N8, or a very, very long shot H5N6), but last November we also saw Algeria: Large Bird Die Off Due To HPAI H7N1 - OIE, so other subtypes are certainly possible. 
We take special note of  large die offs because in the past they have occasionally heralded a change in the virus (i.e.  a new clade, or a novel reassortment).  A few notable examples: 

We ought to learn the subtype from the Ugandan outbreak in the next few days. Even if it is H5N1 or H5N8, it could be weeks or months before we learn if they carry any significant genetic changes.

Meanwhile, assuming that HPAI is confirmed in Uganda by the OIE/FAO, this should put the rest of Sub-Saharan Africa on alert that avian flu could turn up pretty much anywhere on the continent.

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