The ECDC On The Recent Nigeria H5N1 Report Of Suspected Human Infections

#15,904

After going nearly 5 years without reporting any HPAI H5N1, in late 2014 Nigeria and other West African nations began reporting widespread avian flu activity, and this time, it is due to a new - potentially more dangerous - clade of the virus (see EID Journal: HPAI A(H5N1) clade 2.3.2.1c In West Africa).

If you look at a map of the migratory bird flyways at the top of this blog entry, you will see that West Africa sits at the southern intersection of no fewer than three migratory flyways. Routes that begin in the northern climes of Russia, Mongolia, and China where H5N1 is known to circulate in wild birds – and that cross both Europe and the Middle East.

Until now, Western Africa hasn't reported any human infections since a single case in 2007, although that may say more about their testing and surveillance than the impact of the virus.

In the middle of the last decade - in FAO: Concerns Rising Over Spread Of Avian Flu In Africa and 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.

Over the past week there have been media reports of 6 (possibly 7) H5 human infections in Nigeria. Unfortunately, Nigeria's CDC website has been under construction, and when you can get in, most of the links are inoperable.  

Shiloh at FluTrackers began this thread on wednesday , where media reports could be posted, but I've been waiting for something more substantial before posting it here.  We've been burned by reports like these in the past, so I take media reports with an extra-large grain of salt.

While it doesn't confirm these reports, yesterday's EDC Communicable Disease Threats Report acknowledges the Nigerian report, and legitimizes it to some extent. Confirmation will require verification by a WHO Collaborating Centre (which is pending). 

As we've discussed often, it is likely that human infection with HPAI H5N1 (and potentially other) avian flu subtypes has gone undetected in sub-Saharan Africa, so it would not be much of a stretch to believe that several cases have recently been detected in Nigeria.

After three years of relative quiescence, HPAI H5 has been on the ascendent for the past 8 or 9 months, and we've started to see human infections again in China and Southeast Asia and simultaneous epizootics in Europe and in Asia (see ECDC Update: Avian Influenza Epizootic In Europe - December 2020 - February 2021).

And earlier this year, for the very first time, we saw confirmation of human infection with avian H5N8 in Russia (see Russia: Anna Popova On The Potential For H5N8 To Transmit Between Humans).

While we await further world from the WHO, what we know about the (suspected) Nigerian outbreak is summarized below by the ECDC.

New! Influenza A(H5) ±Nigeria ±

Opening date: 7 April 2021 Latest update: 9 April 2021

 Epidemiological summary

In 2021, and as of 28 March, outbreaks of highly pathogenic avian influenza (HPAI) H5N1 in poultry have been reported in 30 farms from seven states in Nigeria: Kano, Plateau, Bauchi, Gombe, Kaduna, Nasarawa, and the Niger states. The Nigerian authorities initiated an outbreak investigation, and a joint team from Nigeria CDC (NCDC) and the Federal Ministry of Agriculture and Rural Development (FMARD) were deployed to Bauchi, Kano, and Plateau states. 

Public health measures have been initiated in the affected states, including biosecurity measures in the poultry farms and sensitisation to farm owners, workers, live bird market associations, and communities.

As of 28 March 2021, 83 human nasopharyngeal/oropharyngeal samples have been collected from contacts of confirmed birds in four states: Kano (27), Bauchi (19), Gombe (19), and Plateau (18). All contacts were farmers, farmworkers, bird-handlers, and traders, and all were asymptomatic. 

Of the 83 collected samples, 64 samples were analysed using real-time RT-PCR (rRT-PCR). From the 64 analysed samples, seven were positive for influenza A virus, including six samples of influenza A(H5) (neuraminidase (NA) remains undetermined) and one sample of unsubtypable influenza A virus.

These seven confirmed samples have been reported in Kano (four) and Plateau (three) states and have been shipped to the WHO Collaborating Centre in the US for further characterisation. In addition, 13 blood samples have been collected from the very-close human contacts of birds in Bauchi (5), Gombe (5), and Plateau (3) states. Sources: Nigeria CDC | media

ECDC assessment 

Different A(H5Nx) viruses are currently circulating in west African countries and confirmation about the respective viral subtype is pending. Available information does not detail symptoms in positive tested people nor any transmission events. More epidemiological and virological details are needed to assess the situation. The risk of zoonotic influenza transmission to the general public in EU/EEA countries is considered to be very low. 

Direct contact with infected birds or a contaminated environment is the most likely source of infection. The use of personal protective measures for people exposed to dead birds or their droppings will minimise the remaining risk. Actions ECDC monitors avian influenza strains through its epidemic intelligence activities in order to identify significant changes in the epidemiology of the virus. ECDC, together with EFSA and the EU reference laboratory for avian influenza, produces a quarterly updated report on the avian influenza situation. The most recent report was published on 26 February

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