Health chiefs are tracking bird flu outbreak ‘very carefully’ after two workers test positive

Bird flu is an ‘ongoing risk’ that must be monitored ‘very carefully’, experts warned this morning.

It comes health officials confirmed yesterday two British poultry workers tested positive for the killer virus earlier this month. 

Neither of the workers experienced any symptoms of avian influenza and have since tested negative for the virus. 

They said one of the persons infected likely tested positive for bird flu after inadvertently inhaling infected material, like faeces, from diseased animals. 

But they added how the second person had come into contact with the virus was currently unclear.

UK scientists tasked with developing ‘scenarios of early human transmission’ of bird flu have warned that five per cent of infected people could die if the virus took off in humans (shown under scenario three).  Under another scenario, the scientists assumed 1 per cent of those infected would be hospitalised and 0.25 per cent would die — similar to how deadly Covid was in autumn 2021 (scenario one). The other saw a death rate of 2.5 per cent (scenario two)

Professor Susan Hopkins, chief medical advisor at UK Health Security Agency (UKHSA), told the BBC Radio 4’s Today programme earlier this morning: ‘Clearly this is an ongoing risk that we need to monitor and watch for very carefully and understand how transmission may occur.’

Both workers have since ‘become negative on PCR swabs’ and it remains ‘uncertain whether they were a true infection’, she added.

A true infection occurs if ‘the virus was replicating in their nose and therefore at risk to others’. 

The virus could otherwise have sat ‘in the back of the nose from contamination,’ she said.

She told the Today programme: ‘We are testing the contacts of individuals, we are offering tests at least to the contacts of individuals. We will continue to do that as part of our surveillance.’

H5N1 — the avian influenza strain behind the current outbreak sweeping the world, considered the biggest ever — does not transmit easily between humans. 

But mutations to the virus that makes mammal-to-mammal transmission easier could change that, some experts have feared. 

Globally, fewer than 900 human cases of H5N1, which kills close to 50 per cent of everyone it strikes, have ever been recorded.

The virus is usually picked up through close contact with an infected bird, whether dead or alive.

Like other forms of flu, humans can get infected if the virus gets into their eyes, nose, mouth or is inhaled.

But with bird flu, this usually occurs in people who spend a lot of time with infected creatures, such as bird handlers. 

A spate of human bird flu cases have emerged in the early parts of 2023.

Earlier this year, a Cambodian man and his daughter were diagnosed with H5N1.

Their cases sparked international concern, with many experts fearing the infection was proof the virus had mutated to infect people better after tearing through the world’s bird population.

Further testing found the Cambodian family did not have the H5N1 strain rapidly spreading among the world’s wild birds — but instead a variant known to spread locally in the Prey Veng province they resided in.

Over 700 confirmed cases of H5N1 have been detected among wild birds in England since September 2022, according to the UKHSA. Pictured above, a bird flu outbreak in February in Queens Park, Heywood, Rochdale

Both the British workers were spotted through routine testing of people came into contact with infected birds, the UKHSA confirmed yesterday. Neither was named. 

The two individuals ‘were tested repeatedly over a period of time’ and ‘were detected as having avian influenza in their nose,’ Professor Hopkins told the Today programme. 

‘What that means is that they’ve got it up their nose, likely from the environment they were in. They manifested no symptoms which is really good and they didn’t transmit to anyone else,’ she added. 

‘We don’t think this increases the risk to the population across the UK at present.’ 

There has only ever previously been one case of a British person becoming infected with H5N1 since the ongoing outbreak took off in October 2021.

Alan Gosling, a retired engineer in Devon, caught the virus in early 2022 after his ducks became infected.

He later tested negative while he was quarantined for nearly three weeks. 

All 160 of Mr Gosling’s ducks — including 20 that lived inside his home — were culled after he tested positive. 

Government advisor, Professor Ian Brown, the director of scientific services at the Animal and Plant Health Agency (APHA), yesterday also said: ‘Deep surveillance programmes of personnel in close contact with infected poultry are insightful to understand what could happen. 

‘To date out of the reported detections in humans it is clear that careful investigation and interpretation is required. 

However he added: ‘Detection by PCR alone does not necessarily prove active infection and supports the virus still remains strongly avian in its tropism but programmes such as those being deployed in Great Britain are valuable to gain better understand of the true risk these viruses currently pose to human health. 

‘The one health joined up approach being applied in Great Britain sets best international practice for vigilance.’ 

The UK Health Security Agency (UKHSA) has currently set the threat level to level three, given there is ‘evidence’ of changes in the virus genome that could trigger ‘mammalian infection’, it said.

Any ‘sustained’ mammal-to-mammal transmission of the pathogen would raise the threat level to four, while human-to-human would push it to five.

Data from the World Health Organization shows that over the last two decades, there have been 873 cases of human infection with H5N1 avian flu virus around the world.