July 13, 2015

expert reaction to reports of confirmed case of the H7N7 bird flu virus at poultry farm in Lancashire

A case of the H7N7 avian flu virus has been confirmed at a farm in Lancashire. The Department for Environment, Food and Rural Affairs (Defra) has announced humane culling of the farm’s birds, and also surveillance zones around the farm.

Dr Colin Butter, Head of Avian Viral Immunology, The Pirbright Institute, said:

“The avian influenza virus found on a Lancashire Poultry farm is of the H7N7 strain and is highly pathogenic in chickens. Birds are being culled by humane means and a statutory ten kilometre surveillance zone and three kilometre protection zone are now in place, limiting the movement of birds.

“In addition to dealing with the immediate problem the important issues are now to determine the exact molecular sequence (the genetic fingerprint) of the virus and to trace contacts between this farm and other poultry facilities. In this way the likely source of the virus can be determined and its further spread limited or eliminated.

“Although bird flu does not readily spread from person to person there has been a limited direct infection of people, particularly with the Highly Pathogenic H5N1 and the Low Pathogenic H7N9 strains. Whilst both of these viruses may cause severe disease or death in people the outcome of infection with other strains, including H7N7, is usually mild symptoms, often limited to conjunctivitis (a local infection of a membrane of the eye). The genetic data may also provide information on the possibility and likely outcome of human infection but while we wait for this it should be considered that there is no immediate risk to the public.”

Dr Derek Gatherer, Lecturer in Bioinformatics, Lancaster University, said:

“The USA has suffered its worst avian influenza outbreak this spring with several million birds being slaughtered in the state of Iowa and other parts of the Midwest. The North American outbreak has been caused by the highly pathogenic H5N2 subtype. Europe has been much luckier. Although the UK has had three identified bird flu outbreaks in the last 12 months, none have been H5N2. We did see the relatively new and pathogenic H5N8 appear last year, which had previously been seen in the Netherlands, but the other two outbreaks have been H7N7 which is less of a concern.

“Nevertheless, it is all bad news for the farmers who will lose their stock and the neighbouring farmers whose businesses will also be severely affected during the restricted movement period. H7N7 is actually the oldest known subtype of influenza, with a partial genome sequence having been retrieved from an Italian duck that died in Brescia in 1902.  Of the 144 subtypes, 122 have been seen at some time or place since then, and we have full genome sequences of 116 of those. There have been occasional infections of humans with H7N7, most recently in Italy in late August 2013, and prior to that in the Netherlands in February 2003. In the latter case there was a fatality due to a pre-existing medical condition in one patient. There is no danger to the general public in the Lancashire outbreak.

“The main concern for the British government will be making sure that the UK and Europe in general, doesn’t suffer the kind of disastrous impact on our poultry industry that the Americans have suffered.  The way to ensure that is stringent and immediate quarantine and culling.”

Prof. Andrew Easton, Professor of Virology, University of Warwick, said:

“The confirmed case of H7N7, otherwise known as bird flu, in Lancashire is a concern because of the potential threat to the UK poultry industry. There is no reason at this stage to believe that there is a threat to humans either directly by infection with the virus or indirectly by the presence of the virus in food. Bird flu in poultry is categorised as being of either low or high risk of disease in domestic birds such as chickens and it is the latter category that is the most concerning.

“Bird flu strains are identified by the nature of two proteins that form part of the virus; there are 16 different types of H protein and 9 types of N protein. In theory these two proteins can be found in any of a total of 144 possible  combinations, though only a relatively small number of these have actually been identified in nature. Of the ones found only a few types have been associated with serious disease in birds. The high risk category can cause fatal infections in birds and spread very rapidly so there is constant surveillance for their presence and emergency procedures that are adopted when a suspected case arises.  It is important that the preventative steps are put in place as quickly as possible to restrict the risk of spread to other farms. This is accompanied by a programme of killing the birds at the suspect premises as a precaution to further limit the risk of spread.

“There is a worldwide surveillance system testing and identifying influenza outbreaks and this provides a very good information network to identify the most serious flu strains.

“Some bird flu strains (e.g. H5N1) have been shown to be capable of infecting humans in rare circumstances. Some of the strains are extremely dangerous and can cause serious disease or death in a high proportion of the infected people. However, while these tragic situations are of concern, to date the viruses involved have not been able to spread efficiently between people and the outbreaks have been sporadic and contained. ”

All our previous output on this subject can be seen at this weblink: http://www.sciencemediacentre.org/tag/avian-flu/

Declared interests

Dr Collin Butter: Dr Butter’s present laboratory at the Pirbright Institute is funded by the BBSRC to work on Avian Influenza.  This will remain part of his research interest when he shortly moves to The University of Lincoln.  

Dr Derek Gatherer:  I am funded by Rosetrees Trust and the NHS to study influenza C in humans.

Prof. Andrew Easton: No interests to declare