A new pandemic could begin when it learns to be transmitted from person to person
In recent months, the global scientific community has been watching with bated breath the mutations of a new strain of the highly pathogenic avian influenza A H5N1 virus, which is spreading (for now) across several American states. The strain is no longer fully avian — it actively circulates among cows, and not long ago it was discovered in milk; It infects cats, mice, and now humans.
Photo: ru.freepik.com
In recent decades, scientists have linked pandemic predictions specifically to bird flu. It was supposed to start as soon as the virus learned to transmit from person to person. And today, some scientists are worried: it looks like this has happened.
Let us recall that all pandemics of the 20th century were caused by new variants of the virus containing genes from human and avian strains. Suffice it to remember the “Spanish flu” (1918–1919), which affected a third of the world's population and which claimed the lives of 50-100 million people. Today, scientists believe that the H5 subtype virus has never circulated in the human population, and therefore poses a global threat to the world's population. Just a few years ago, the influenza A virus of the H5N1 subtype occupied an ecological niche in the poultry population in Southeast Asia, where the possibility of a pandemic virus emerging is especially great. In 2005, variants of the influenza A H5N1 virus carried by migratory birds entered northern Eurasia (including Russia), and then into Europe, the Caucasus, the Middle East, Central Asia and Africa. Until now, humans have been infected from birds, and so far transmission of the virus from person to person has not been proven. However, in recent years, all (albeit rare) cases of human infection with H5N1 A strains have been accompanied by extremely high mortality (over 60%). Therefore, WHO experts assessed the situation as a real threat of a new pandemic.
Today, the genetic variant of bird flu 2.3.4.4b is causing concern, having successfully «jumped» from birds to mammals — first to wild ones, and then to domestic ones, or more precisely, to dairy cows on several dozen farms in different states of the USA. In addition, the virus was found in the milk ducts and respiratory tract of cows that have no external manifestations of the infection. It was also found in cats, and recently — in mice.
And in July, reports began coming in of workers at farms where bird flu had been detected, with respiratory symptoms. Several of them were confirmed to be infected with H5N1. Who they got the infection from is the question. Until now, the virus had only been transmitted to people from birds. Here, sequencing showed that the virus's genetic material was the same as that of infected cows. This means that just a few mutations and the virus will learn to transmit from person to person. Or maybe it already has.
“Is bird flu already spreading between people?” asks American scientist and geneticist Dmitry Prus. – And what will happen when this virus finally learns not only to infect certain mammalian cells, but also to be transmitted through the respiratory tract, as epidemic flu does? It seems to me that this should happen in the coming months.”
One of the main symptoms in infected people was conjunctivitis – Recently, American media reported an outbreak of conjunctivitis (“pink eye”) with hemorrhages and positive rapid tests for influenza A on a farm in Oregon. “Let me remind you that at this stage, the avian virus, which is not yet sufficiently accustomed to the human body, most often affects the mucous membrane of the eye, and cases of direct transmission of the virus from person to person have not yet been officially established. Patients from Oregon tried to draw the attention of the CDC (analogous to Rospotrebnadzor — author) to an outbreak of conjunctivitis, but were told that seasonal flu was in July, nothing surprising, and contagious conjunctivitis was also nothing surprising, so there would be no tests for H5N1. This, of course, is unpleasantly reminiscent of the same CDC in 2020, when no one was tested for covid who was not in contact with the few already identified cases. Like, fewer tests means less worry,” continues Prus.
Is there any reason to worry? Maybe it will pass after all?
20 years ago, an outbreak of the same type of virus swept through poultry farms in Vietnam, killing at least 10 workers who became infected from the birds. Fortunately, the virus had not learned to spread between humans or other mammals. Today's virus, a different subtype of H5N1, has already managed to partially overcome this critical barrier (it spreads between mammals, but fortunately not through the respiratory tract). But the symptoms in infected people are relatively mild (conjunctivitis and mild malaise).
«On the one hand, it is known that about half of the recent cases of H5N1 bird flu in humans were fatal. On the other hand, if no one was tested for this virus except in exceptional cases, then it is clear that the statistics are enriched with severe infections and that the real mortality rate should be significantly lower. And unlike COVID at the dawn of the pandemic, people have a certain natural immunity to H5N1 (mainly those born before 1968, when there was a pandemic of a related virus), there are drugs (antiviral drugs such as oseltamivir should also work against the new flu; resistance mutations have not yet been found in them) and even a vaccine (the world has a small stock of traditional vaccines against H5N1, which, with proper planning, can successfully suppress the first local outbreaks of this flu). Additional doses are being produced, but this is not nearly enough to immunize the entire population. However, in America, developments are already underway for a more widespread mRNA vaccine: the government has allocated funds to several pharmaceutical companies for this purpose,» the scientist says.
Свежие комментарии