Cases are increasing of the H5N1 strain of avian influenza spreading to mammals, and new figures suggest that over half of human infections of the virus over the past 20 years have proved fatal.

A new report in the British Medical Journal reveals that 53% of humans who have caught the H5N1 strain of avian influenza since 2003 have died from the disease. In contrast, Covid has a mortality rate of 3.4% and seasonal flu less than 1%.

A leading testing expert says this is why the virus must be taken extremely seriously. Dr Quinton Fivelman, chief scientific officer at London Medical Laboratory, said: “We’re becoming used to outbreaks of the H5N1 strain of avian influenza, generally known as avian or bird flu, in UK poultry farms. We must not let familiarity mean we become content with this situation. 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.”

Avian flu was first detected among chickens in Scotland in 1959. In 1997, the first human cases were recorded in Hong Kong and China, where 18 people were infected and six died. Since 2003, there have been 860 human cases of infection and 53% of these have died.

Fivelman added: “In the UK, there has only been one recorded case of the H5N1 strain in humans. A British man contracted the virus early last year. Duck expert Alan Gosling, who was 79 when he caught it, was believed to have contracted the H5N1 strain of avian flu from his Muscovy ducks. Happily, he is one of the 47% who have survived the illness. Previous UK cases were all of the H7 strain of avian influenza.

“However, the crossover from birds to mammals is increasingly concerning. There is a growing realisation that what were thought to be isolated incidents are becoming more commonplace. This month, the World Organisation for Animal Health reported that the rising number of cases in mammals had caused ‘morbidity and mortality’ in species such as otters and seals. 600 sea lions off the coast of Peru have also died from the virus. In the UK, otters and foxes have been found to have the H5N1 strain.”

According to the European Centre for Disease Control, around 50m birds, including poultry, have so far been killed by the virus or culled in this outbreak. WOAH has warned that the disease is no longer a seasonal problem, but one that can occur all year round. Gregorio Torres, head of the science department at WOAH, said: “The seasonality we [used to] observe isn’t there anymore.”

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