The UK Health Security Agency (UKHSA) has said there is “no evidence” that the bird flu virus is an imminent threat or can spread between people, despite growing worries about the risk of a possible bird flu pandemic.
The move, in a technical briefing, has come as the World Health Organization (WHO) has urged heightened vigilance from all countries following the death of an 11-year-old girl in Cambodia from the H5N1 virus.
A report in the British Medical Journal has revealed that 53% of humans who have caught the H5N1 strain of avian influenza since 2003 have died from the disease, highlighting the seriousness of the situation if bird flu does leap to become a human transmissable disease.
By comparison, Covid-19 has a mortality rate of 3.4% and seasonal flu less than 1%.
The UKHSA said that, while the very high levels of transmission in wild birds present a constant risk, “there is no evidence so far that the virus is getting better at infecting humans or other mammals”.
People who have come into contact with infected birds enter a period of monitoring by UKHSA health protection teams, with the level of monitoring dependent of whether individuals were wearing adequate PPE.
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Between 1 October 2022 and 14 February 2023, 2,310 people were monitored through this process, with samples taken from people who developed any flu or cold-like symptoms in the 21 days following their contact with an infected bird. No positive cases have been found to date.
Dr Meera Chand, incident director for avian influenza at UKHSA, said: “The latest evidence suggests that the avian influenza viruses we’re seeing circulating in birds do not currently spread easily to people. However, viruses constantly evolve, and we remain vigilant for any evidence of changing risk to the population, as well as working with partners to address gaps in the scientific evidence.”
However, Dr Sylvie Briand, director of epidemic and pandemic preparedness and prevention at the WHO, described the current situation as “worrying” because of the recent rise in cases in birds and mammals.
Authorities in Cambodia last week reported the death of an 11-year-old girl from the H5N1 bird flu, with her father also testing positive for the virus.
Dr Briand said it was not yet clear whether there had been any human-to-human transmission, which was a key reason to focus on the cases in Cambodia, or if the two cases were due to the “same environmental conditions” likely close contact with infected birds or other animals.
However, the report in the BMJ has highlighted the severity of the virus in humans, and therefore the potential danger of bird flu.
Dr Quinton Fivelman, chief scientific officer at London Medical Laboratory, said of the study: “We’re becoming used to outbreaks of the H5N1 strain of avian influenza, generally known as avian or bird flu, in UK poultry farms.
“The fact that it is now spreading to mammals across the globe shows we cannot let our guard down against the spread of this virus.
“Bird flu is spread by close contact with an infected bird (dead or alive). You can’t catch it through eating properly cooked poultry or eggs. However, anyone who works with birds or who finds a sickly bird must be vigilant and take extra precautions.”