In the past few days, the United States, Canada, Chile and Peru have reported mass deaths among sea lions and gray seals as a result of the bird flu that is currently circulating. 3,500 sea lions have died in Peru alone. For months, the worst ever documented wave of bird flu in birds – also known as avian influenza or avian influenza – has been rampant, which can also infect mammals. Most of the time, these are individual proofs.
The current outbreak of strain H5N1 (2.3.4.4b) has killed a record number of birds and infected mammals and is spreading across several continents, including Europe. Belgium reported infected people at the weekend Red foxes, martens and European polecat felling.
Wild waterfowl are the natural pathogen reservoir, but all types of poultry, many ornamental and wild bird species can become infected. Ducks, geese and some wild bird species show no or only mild symptoms, but the disease is highly contagious for poultry and chickens or turkeys can become seriously ill.
Human cases remain very rare: national health authorities around the world have said the risk of human-to-human transmission remains low. There is currently a vaccine approved in the EU, but it is based on an ancient strain of the virus.
million vaccines
Like the news agency Reuters on Monday reported, the three vaccine manufacturers GSK, Moderna and CSL Seqirus announced on request that as a precaution against a future pandemic they are already developing or testing human trial vaccines that better match the circulating subtype. Other pharmaceutical companies, such as Sanofi, said they were “ready” to start production if needed, as they already had existing H5N1 vaccine strains in stock.
The companies are also pushing to develop an avian flu vaccine for poultry: a market potentially much larger than that for humans.
Less reassuringly, however, is that most potential human vaccine doses are earmarked in long-term supply contracts for wealthy countries, global health experts told Reuters.
“We could have a much bigger problem with vaccine hoarding and vaccine nationalism in a flu outbreak than we saw with Covid-19,” said Richard Hatchett, executive director of the Coalition for Epidemic Preparedness Innovations (CEPI), which is co-funding the vaccine research.
Data analysis in seals
Avian influenza has been continuously monitored with testing in birds and some mammals in New England since January 2022. According to this, in June and July 2022 alone, more than 330 harbor and gray seals died from bird flu line 2.3.4.4b along the North Atlantic coast. A research team from Tufts University in Medford (USA) recently published data on pathogen analyzes of samples from dead, sick and healthy animals in the specialist journal Emerging Infectious Diseases.
Sometimes there are samples in pairs, sometimes from a bird and a seal on the same beach: a seal can become infected if it comes into contact with excrement from a sick bird or with water contaminated by it, or if it eats an infected bird.
It is known that H5N1 is almost 100 percent deadly in waterfowl. The study now shows that this could also apply to mammals: all seals that tested positive for the virus were already dead at the time the sample was taken or succumbed to the pathogen shortly afterwards.
The question of whether the virus is also transmitted between seals is still being discussed: “It would not be surprising if transmission between seals can occur, since this was already the case with low-pathogenic bird flu,” said Wendy Puryear. However, definitive evidence is still lacking – for seals and generally for transmission from mammal to mammal.
Experts are concerned that the virus could adapt better to mammals and thus to humans. Experts were concerned about an outbreak of bird flu on a Spanish mink farm in October 2022. There are indications in the animals that the pathogen has adapted genetically better to mammals, it said. It is not yet clear whether there was transmission from animal to animal in the farm or another route of infection, for example via food.
Mammal-to-mammal transmission would pose a higher risk to humans.