Should we be worried about the UK’s first human case of H5 avian flu?

As the UK battles its largest ever outbreak of avian influenza, with 66 cases in England and 79 across the UK, last week also saw a rare human infection with the ‘H5’ influenza type found in birds.

The case was confirmed in 79-year-old duck expert Alan Gosling who kept 20 of his ducks in his home, and over 100 outdoors, according to a report in DevonLive. Shortly before Christmas, 160 local ducks tested positive for H5N1.

While Mr Gosling is reportedly well and self-isolating, with no evidence of onward spread – which is also very rare in such cases – the incident is potentially concerning, especially in light of the high levels of H5N1 in the UK.

Coventry University virologist Dr Gould, who has been researching influenza for the past five years, notes that human cases are rare. Although there are quite a few annual cases in Asia – where poultry is often bought live and killed at home after close contact – this is the UK’s first case of the H5 strain.

Why is this a rare occurrence?

In order to replicate, a virus needs to attach to cells in a human or animal and it uses the proteins on the outside of the spherical structure seen in a typical virus illustration. Viruses currently circulating in humans such as H1N1 (swine flu) and H3N2 have evolved to specifically target human cells, meaning the virus is highly transmissible between humans – and the same is true for viruses affecting birds.

To infect, the virus has to bind on a sugar molecule outside cells – but this varies between humans and birds. “That tends to mean a bird flu virus is very good at infecting birds but very ineffective at being able to infect and replicate in a human, because those sugar molecules on the outside are subtly different,” Dr Gould explains.

This prevents the virus jumping between species, but if the virus can jump into a human, it’s a real concern as we will have no immunity to it – something with which the global population is now highly familiar, due to Covid-19. “That is the biggest fear with these strains of bird flu,” Dr Gould adds.

Wider concerns

Another concern is of course that if the species can jump into a human, it can then spread from human-to-human thereafter, which again, is very rare. In the case of swine flu, which caused the 2009 pandemic, reassortment occurred when bird flu, human flu and swine flu emerged in one animal.

The influenza genome is comprised of eight segments, so if two or more different viruses get into one cell, you can end up with new viruses comprised of the two different genomes, Dr Gould explains.

“This is why we need these really strict rules because the consequences of ignoring it could be really severe. What we don’t want is an avian virus to spread, which gives more opportunity for it to reassort and combine with different circulating strains or infect a human and replicate, which could cause more disease because we have no natural immunity.”

What is the risk to farmers?

Commenting on the risks to keepers of infected birds, Dr Gould says that while this type of species jump is rare, it is a case of risk probability: “There’s an opportunity in those locations for someone dealing with a population of poultry where they could be infected.

“Overall, the risk is limited but farmers have higher risk as they are dealing with live poultry in large numbers. If someone has got a flock of say 10,000 chickens in a barn and bird flu starts spreading, clearly there is a large opportunity for that to be spread so it’s all about managing the risks.”

Commenting on the case, the UK Health Security Agency said the ongoing overall risk to human health remains very low and there is currently no evidence that the H5 strain can spread from person to person.

Mr Gosling’s specific exposure to infected birds ‘is considered to be very different to other infected premises with confirmed avian influenza in the UK’, the statement added. The infection was acquired from very close, regular contact with a large number of birds infected with the H5N1 strain, which were kept in and around the home over a prolonged period of time.

There have been fewer than five recorded human cases of avian flu in the UK, with the last recorded case in 2006. Previous cases were confirmed as the H7 strain – this is the first time H5 has been detected in a human in the UK.

For the latest avian flu updates and advice visit: www.gov.uk/guidance/avian-influenza-bird-flu#latest-situation

Bird keepers should report suspicion of disease in England to Defra Rural Services Helpline on 03000 200 301, in Wales contact 0300 303 8268. In Scotland, contact your local Field Services Office. In Northern Ireland contact DAERA on 0300 200 7840.

Keep an eye out for upcoming advice on keeping safe for poultry keepers.

Are you concerned about this recent case and the ongoing outbreak of H5N1? Share your experiences with us at views@farmersguide.co.uk