[ad_1]
There has been a lot of talk lately about bird flu. And for good reason: this year’s is proving to be one of the worst flu epidemics ever for birds, both in populations of birds wildboth in the farms half the world. That’s not all, because a particularly aggressive outbreak broke out in October on a Spanish mink farm has rekindled fears that the H5N1 virusthe deadliest of those that cause bird flu, can adapt to improve its ability to infect mammalswith the risk that it makes a real leap of species and gives rise to one pandemic whose potential scope is currently not easy to predict. It’s too early to worry – the experts assure – but it is still a situation to keep under control. Let’s see what we know.
The bird flu virus
H5N1 is a virus that belongs to the subgroup A of influenza. It can infect many animal species (including ours), but it is mainly known as the etiological agent ofbird flubecause since 1996, a viral strain has appeared highly pathogenic in birds (but poorly infectious to mammals), which periodically causes epidemics worldwide. After the first characterizations in China in ’96and an epidemic ad Hong Kong the following year in which the first cases of human infection were recorded, the virus continued to change until the appearance in 2004 of the so-called Z genotypeextremely infectious and capable of causing very serious symptoms (in birds), with a lethality rate approaching 100% for the farm chickenswhich in the following years spread rapidly, becoming the prevalent genotype all over the world.
A dramatic epizootic
Like all virus influence themalso that offlu it accumulates mutations quickly as it moves from host to host. And it reappears periodically with more or less severe years, also depending on the prevailing viral genotype. From the 2021 a particularly insidious virus began to circulate, which continued to reap victims even this year. Last year the count had already reached over 77 million Of farm chickens slaughtered due to flu, and more than 400 thousand birds of species other than poultry (wild and otherwise) who died from the virus. This year, since the beginning of October, birds killed by the disease or culled to prevent its spread have already exceeded the quota 100 million. The hardest hit country was Great Britain, where it has become almost impossible find eggs, especially if they come from free-range hens. In shetland islandsin northern Scotland, bird flu nearly killed the 40% of the local population of major skuas (Stercorarius skua), leading to fears for the survival of the entire species.
Also in Greece the epidemic of 2021/2022 hit hard, killing more than 500 specimens Of pelican frizzy wild. As well as in Israelwith over 6 thousand gray cranes found dead over the winter. After the warm season, bird flu tightened its grip again: in the USA and in Canada the number of wild birds killed by the flu was the highest since the virus was discovered. And even the United Kingdom this year has registered the worst epizootic (Meaning what an animal epidemic) of all time regarding the influence, which prompted the government to enact a real lockdown of the poultrywhich forced farmers to keep birds indoors to avoid the risk of contagion from wild animals.
The outbreak among ferrets
During bird flu epidemics it is not uncommon for the virus to infect as well different animals from the birds from which it takes its name. Usually in mammals his replication And less efficientand therefore infections typically occur when a animal wild feeds directly on birds infectedwhile I contagion secondary (from mammal to mammal) are practically unknown. This is why the incident that took place in October inSpanish mink farm has been studied with extreme attention by the scientific community: the high number of infections suggests the presence of a virus that has developed a high affinity for mammals (or at least for poor mink), and therefore much more dangerous also for our kind.
In Spanish breeding, the virus has shown a relatively high lethality (up to 4.3% of the total population in the worst weeks), linked to the onset of pneumonia hemorrhagic And malfunctions pulmonary of another type. And the analysis of genome viral (published on Eurosurveillance) revealed the appearance of a mutation potentially linked to an adaptation of the virus to the new host (the mink), which could therefore explain the ease with which the disease spread among the animals after the initial infection, which probably occurred with the casual entry of an infected bird into the sheds in which they are kept. Certainties obviously there are none, and all the personal of the Spanish company is result negative to the H5N1 virus. All the mink on the farm were also culled to contain the further circulation of the virus, and as there were no new cases in the following months, it is probable that the intervention has borne the desired results. Having said that, it is, as we said, a previous worrying: an avian virus adapted to infect ferrets would in fact be much more likely to acquire the ability to spread from man to man too. And with an effective species jump, there are fears that an avian flu pandemic could have devastating effects.
The virus in humans
What scares experts is the fact that H5N1 in man, although rare, they seem to have a lethality particularly high. On 868 infections confirmed humans between January 2003 and November 2022, i deaths indeed they were 457which means that the virus in humans could have a mortality of 53%. Scary numbers in the event of a pandemic, but which is good to take cum grano salis. Infections in humans up to now have always been occasional, and linked to contact with infected animals (direct infection from man to man has never been confirmed). And since it is not a virus that is routinely searched for in the event of illness, anywhere in the world, it is inevitable that the account will be affected by what comes bias Of sampling: only in the case of severe symptoms is it likely that a swab for the H5N1 virus will be performed, and if the infections asymptomatic or paucisymptomaticas it is realistic to imagine, have actually been many more than those confirmed, the lethality of the virus could be drastically lower than what official statistics give us.
“At present, the WHO assessment of the risk it poses to humans remains low”, he said in the past few weeks the director of WHO Tedros Adhanom Ghebreyesusbut adding that “However, we cannot assume that this will always be the case, and we must therefore be prepared for any change in this state of affairs.”. As? Carefully monitoring the variants viral In circulation, reducing the contacts between humans and infected animals, making safer The farms (such as those of minks), and promoting the development of drugs and vaccines with which to be ready in case the virus becomes truly capable of transmitting between humans.
.
[ad_2]
Source link
