January 6, 2022

expert reaction to person with bird flu

The UK Health Security Agency (UKHSA) has confirmed a case of avian influenza in a person in the South West of England.

Prof Ian H Brown, Head of Virology at the Animal and Plant Health Agency (APHA), said:

“The detection of H5 avian influenza virus in a human is the first of its type in the UK. There have been a very small number of human cases over the years but all with other serotypes (H7) not H5. This is the first reported human case with this particular strain of H5N1 so is an extremely rare event, even though this virus is currently affecting bird populations across Asia, Europe and Africa in particular. The case is likely due to unusual and continuous exposure to a large number of kept H5 infected birds in and around the home of this person. The infected birds have been humanely culled. There is no cause for undue alarm since the risk from this strain to people is considered very low and there is no evidence that this virus is able to transmit from one person to another. It is important to emphasise that the public should avoid touching sick or dead wild birds that may be carrying the virus as a precautionary measure.”

Prof Malcolm Bennett, Professor of Zoonotic and Emerging Disease, University of Nottingham, said:

“As the comments from UKHSA and Defra make clear, there are many strains and types of avian influenza, some of which occasionally jump species, including into humans.  When this does occur, usually little disease or onward transmission occurs, but it’s obviously something that’s looked out for as, very rarely, these viruses can become established in humans or, indeed, other mammals – and although very rare,  such events are the ultimate source of the major human influenza pandemics.  

“As well as the direct disease risk posed by human infection, there is also the possibility of avian influenza viruses reassorting (a form of recombination) with human, or other mammalian, influenza viruses in a doubly-infected individual, giving rise to new strains that combine the human virus’s ability to infect and be transmitted among people with antigens from the bird virus, antigens to which we don’t have pre-existing immunity.  Hence the particular importance of treating quickly anyone infected and also of those working with wild  birds or poultry getting vaccinated (so they are less likely to be infected with circulating human strains).

“Avian influenza outbreaks – at least as clinical disease in birds – occur in British birds, mainly waterfowl and then poultry, most winters and are probably associated with migrating waterfowl. The number of outbreaks, and the length of the season over which they occur, seem to have increased in recent years, possibly associated with climate change. Not all birds are equally susceptible either to infection or disease, and so silent infection may be even more common than we know (surveillance of wild birds is largely based on testing those found ill or dead). It may be that we are approaching the point when instead of thinking about avian influenza as an exotic disease to be controlled by culling domestic birds, we need to think about it as something seasonally ‘normal’ to be controlled by immunisation.”

Dr Holly Shelton, Head of the Influenza Viruses Group at The Pirbright Institute, said:

“The identification of a human case of the avian strain of H5N1 influenza virus is rare but has happened in the past.

“The UKHSA has stated this infection was the result of prolonged contact with a large number of infected birds. These circumstances that have resulted in infection of this individual directly from birds is the common mechanism when human cases of H5N1 are identified in other countries. A large infectious dose is required to infect a human with an avian influenza virus as there are significant barriers that the virus must overcome in order to establish infection. Human to human transmission of H5N1 avian influenza viruses are extremely rare and there is nothing in the genetic makeup of the most recent H5N1 avian influenza strain reported in the UK that suggest this virus would be capable of efficient and effective human to human transmission.

“Birds and humans are very different and influenza viruses must adapt and change in order for avian viruses to establish transmission in humans. The proteins that the virus interacts with inside the infected cells are different in humans and birds and consequently avian viruses find it hard to replicate themselves in humans. In addition, the behaviour of humans and birds means the transmission routes are different as well with water carrying faecal matter playing a large role in the transmission of avian influenza between birds, whilst between humans, transmission via droplets in the air to the common transmission mechanism, again the virus must alter itself to facilitate the different transmission modes.”

Prof Paul Wigley, Professor of Avian Infection & Immunity at the University of Liverpool, said:

“Whilst avian influenza has the potential to be transmitted from poultry to humans it is very rare and, as in this case, usually due to close and long-term contact with infected birds. Avian influenza such as the H5 serotype is largely adapted to infect birds and so is very unlikely to be transmitted from person-to-person. The advice given by APHA and UKHSA over contact with infected birds is sensible and should be followed. The risk of wider infection in the general public remains low.’

Prof Ian Jones, virologist at the University of Reading, said:

“Transfer of avian flu to people is rare as it requires direct contact between an infected, usually dead, bird and the individual concerned. It is a risk for the handlers who are charged with the disposal of carcasses after an outbreak but the virus does not spread generally and poses little threat. It does not behave like the seasonal flu we are used to.

“Despite the current heightened concern around viruses there is no risk to chicken meat or eggs and no need for public alarm.”

Prof Mike Tildesley, professor in infectious disease modelling at the University of Warwick, said:

“This is clearly going to be big news but the key thing is that human infections with H5N1 are really rare (fewer than 1000 worldwide since 2003) and they almost always occur as a result of direct, long term contact with poultry. It can result in a nasty infection for the individual concerned but there has never been any evidence of sustained human to human transmission of H5N1 so at present I wouldn’t consider this to be a significant public health risk.”

https://ukhsa-newsroom.prgloo.com/news/avian-flu-human-case-detected-in-uk

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