Fears of a new pandemic have been raised in a horror study which suggests the world isn’t doing enough to monitor the spread of a deadly flu virus.
A study of bird flu transmission between mammals led by The Pirbright Institute suggests global control measures for the H5N1 avian flu virus aren’t strong enough.
H5N1 was confined to poultry in Asia but has spread around the world and leapt to species of mammals, including cows, seals, mink and cats. A new strain of H5N1 in wild birds has been detected in Europe, Africa, North America, South America and the Antarctic.
Wild birds have introduced H5N1 into dairy cattle and marine mammals, with its growing presence in the environment increasing the risk of people being exposed and possibly catching it.
The first evidence of a spread between mammals was in a mink farm in Spain. This was followed by a second outbreak at 71 fur farms in Finland.
In early 2023, the virus was found in sea lions in Peru and Chile. It then spread through Argentina, Uruguay and Brazil, with experts identifying viral mutations not present in birds.
Dairy farmers in Texas saw reduced milk production from February this year, with H5N1 identified as the cause. That outbreak spread to New Mexico, Oklahoma, Colorado, Kansas, Idaho and seven other US states.
Thirteen human cases linked to that bovine strain were identified as of July 26, according to the study.
A fourteenth person caught bird flu and was hospitalised in August due to underlying health conditions. That individual, from Missouri, suffered chest pain, nausea, vomiting, diarrhoea and weakness.
Partial genetic sequences from the virus in the Missouri patient were similar to the same segments in viruses isolated from US dairy cows, according to the Centers for Disease Control and Prevention.
Since 2020, fewer than 20 human cases have been found in Europe and the Americas. The 13 US cases mentioned in the study were confirmed from a total of 200 people tested by US public health agencies between March and July.
The study’s authors note that it isn’t clear how many exposed dairy workers haven’t been tested, raising questions about whether there has been any limited human-to-human spread.
Symptoms in US farmers have been mild to date, the study notes, possibly because the route of infection is through the eyes. The study says the severity of the disease and symptoms could change if viruses adapt further and infect the respiratory tract.
Led by Dr Thomas Peacock, the authors of the peer-reviewed paper published in Nature have raised questions about whether or not humans are next given bird flu’s rapid spread, fast evolution and spillover into land and marine mammals.
In their review, Dr Peacock and his team identify potential gaps in control measures, issues around vaccine engagement, surveillance and data around the transmission of H5N1 between cows and dairy farm workers in the US.
Testing for H5N1 in wildlife has been focused on carcasses and not live animals, which the paper suggests presents opportunities for variants to spread undetected.
The report’s authors state: “The H5N1 panzootic has been defined by powerful visuals of beaches littered with sea lion carcasses or barns of ill dairy cows wasting away after going off feed.
“But what keeps scientists up at night is the possibility of unseen chains of transmission silently spreading through farm worker barracks, swine barns, or developing countries, evolving under the radar because testing criteria are narrow, government authorities are feared, or resources are thin.”
In its latest assessment, the UK Health Security Agency (UKHSA) said there is no evidence of sustained human-to-human transmission and there were no detected severe human cases linked to H5N1 in the UK as of July this year.
UKHSA Chief Medical Advisor Dr Susan Hopkins said the recent outbreak in US dairy cattle demonstrates that influenza A(H5N1) continues to infect new mammals and spread between them.
She explained: “While the current risk to the UK population from influenza A(H5N1) virus remains very low, an outbreak of this kind can increase the opportunities the virus has to evolve to spread between people at some point in the future. This is because the virus may adapt directly during transmission between mammals or may reassort with other flu viruses in humans or other mammals.
Dr Hopkins said UKHSA will continue to monitor the situation closely alongside Defra, DHSC, Animal and Plant Health Agency and Food Standards Agency.
The chief medical advisor added: “UKHSA has established preparations in place for detections of human cases of avian flu and stands ready to initiate an appropriate public health response should it be needed.”
