Avian flu: H5N1 virus could cause next pandemic – 03/30/2023 – Health

In recent weeks, H5N1 influenza, the virus that causes avian flu, has once again made headlines around the world.

From the coastal cities of Dagestan, Russia, to the coast of Peru, passing through mink farms in Spain and poultry farms in the United States, there were several recorded episodes of millions of animals that died (or were sacrificed) after having contact with this infectious agent. .

Although the risk is still considered small, health agencies and researchers around the world have raised the level of alert about this type of influenza and its potential to cause the next pandemic.

“If H5N1 gains the ability to be transmitted from one person to another, this could be one of the most serious problems humanity has ever faced”, says virologist Edison Luiz Durigon, professor at the Institute of Biomedical Sciences at the University of São Paulo (ICB-USP).

The good news is that, contrary to what happened with Covid-19, governments and health services already have defined plans on what to do if an H5N1 breakthrough becomes a reality – some vaccines are even ready or in development. now.

But, after all, what makes this virus so worrying? And why has he come back to the fore recently?

A massive outbreak

The World Organization for Animal Health estimates that, since October 2021, there have been more than 42 million cases of H5N1 infection in birds.

In that period, about 15 million domestic birds died as a result of this flu – and another 193 million needed to be euthanized.

This is therefore the worst outbreak of avian flu on record since this virus was first identified.

H5N1 has been known since 1996, when it was detected by scientists in China and Hong Kong.

But he gained international prominence from 2005 onwards, the year in which the mortality of chickens raised on farms in Asia rose dramatically. At the time, episodes of infection in humans were also recorded – all those affected had direct contact with sick birds.

Outbreaks are also spreading around the world: before, they were concentrated in Asia and Europe; more recently, they began to affect the Americas — for now, only Brazil and Paraguay have not had confirmed cases of the infection in South America.

The increase in circulation is related to migratory birds, which go from one continent to another according to the season of the year. Many of them travel infected and, when they arrive in a new place, they have contact with the local species.

From that proximity, the virus begins to circulate in a new region — and can reach the farms, which concentrate large numbers of birds in closed warehouses.

Veterinarian Helena Lage Ferreira, president of the Brazilian Society of Virology, explains that the H5N1 influenza underwent “genetic diversification”.

“The subtype that is causing the current problem belongs to the 2.3.4.4b clade. It presents some genetic mutations that made the virus more transmissible among birds”, he points out.

The “clade” cited by the expert is a term that comes close to the meaning of groups or variants, which became well known because of the coronavirus and its lineages, such as omicron, gamma and delta.

“H5N1 is different from all the others. In birds, it causes a serious infection, with respiratory symptoms, such as pneumonia, and even neurological signs”, describes Ferreira, who is also a professor at USP.

The ‘leap’ to other species

In addition to the very high number of birds affected in the last two years, what has drawn the attention of scientists more recently is the number of mammals that are also becoming infected with H5N1.

To date, cases of flu related to this type of influenza have been confirmed in bears, foxes, skunks, raccoons, minks, seals, dolphins and sea lions.

In most of these cases, infection occurs through close contact between birds and these mammals.

Many of them share the same habitat — close contact facilitates the transmission of the virus between species of these two classes of animals.

That is: most of the time, H5N1 is transmitted directly from birds to mammals through body fluids (such as droplets of saliva or feces) or by predation, in which one species hunts and feeds on the other.

Recently, however, two episodes have signaled that H5N1 may be gradually acquiring the ability to transmit from one mammal to another.

The first of these took place in Galicia, in northwest Spain. In October 2022, those responsible for a farm notified the authorities about the transmission of this influenza among minks (or minks), a type of animal raised for the manufacture of coats.

This was the first occasion on which the transmission of H5N1 between mammals (without the intermediation of birds) was officially confirmed. None of the humans that came into contact with the minks got sick.

The second episode took place off the coast of Peru, in which more than 3,400 sea lions died from avian flu.

These deaths on the Peruvian coast are still under investigation to determine whether the transmission chain directly involved the birds —or H5N1 also began to be transmitted among sea lions.

For microbiologist Marilda Mendonça de Siqueira, head of the Laboratory of Respiratory Viruses and Measles at the Oswaldo Cruz Institute (IOC-FioCruz), all these observations are “worrying”.

“To infect, the viruses need to adapt to the conditions of the host”, he teaches.

“In addition to being able to fit into the cell receptors of the new species, influenza needs to adapt to the temperature and pH conditions of each organism, which are different in birds and mammals.”

In other words, this pathogen has gone through — and is going through — a series of transformations in its genetic material that may facilitate “jumping”, or transmission between other species, in addition to those in which it was already frequently observed.

“And this causes concern, as the conditions of the organism of human beings are much closer to those of other mammals than birds”, adds Siqueira.

the size of the danger

According to the World Health Organization (WHO), between 2003 and March 2022, 864 cases and 456 deaths caused by H5N1 in humans were recorded.

The US Center for Disease Control and Prevention (CDC) estimates that between January 2022 and March 2023, ten people were diagnosed with avian flu. Two of them died.

These last cases happened in Cambodia, China, Spain, Ecuador, United Kingdom, United States and Vietnam.

Although the numbers are small, they allow us to calculate a very high mortality rate: overall, 52% of people who were infected with H5N1 died.

“When we see these more recent cases, linked mainly to the 2.3.4.4b clade, the observed mortality is lower, 20%. Even so, it is something that worries”, ponders Ferreira.

For comparison, the current mortality rate for Sars-CoV-2, the coronavirus that causes Covid-19, is around 1%.

“Influenza viruses usually replicate in the upper airways and lungs. The H5N1 seems to go further and reach other vital organs, such as the brain, heart, liver, spleen and kidneys”, details Durigon.

“Death certificates for common flu usually say that the individual died of pulmonary infection or pneumonia. As for H5N1, the cause of death is usually described as ‘multiple organ failure'”, adds the virologist.

Let it be clear: cases of avian flu in humans are sporadic and are all related to close contact with infected animals on farms or in the wild. So far, no direct chain of transmission of this influenza from one person to another has been recorded.

For that to happen, H5N1 would need to mutate — or recombine with other types of influenza that affect people or other species (such as poultry and pigs).

But could that ever happen?

“I would say that there is uncertainty, but we have never been so close to such a scenario. And an H5N1 pandemic would be a tragedy”, warns Durigon.

“H5N1 is a candidate for causing a future pandemic. The question here is not ‘if’ this will happen, but ‘when'”, says Siqueira.

What to do?

The British doctor Jeremy Farrar, chief scientist of the WHO, seems to agree with the view of the Brazilian specialists.

In a recent interview, he called H5N1 “a big concern” and suggested that more action must be taken to prepare the world for the next pandemic.

“If an outbreak of H5N1 in humans starts in Europe, the Middle East, the United States or Mexico tomorrow, we would not be able to vaccinate everyone in 2023,” he estimated.

Researchers heard by BBC News Brasil consider that, contrary to what happened with Covid-19, international institutions and governments are more prepared to deal with a possible crisis caused by the influenza virus.

“The WHO has had contingency plans for an influenza pandemic since the 1950s”, recalls Siqueira.

This organization involves surveillance and laboratory analysis networks around the world. The purpose here is to detect the virus quickly, before it spreads.

An example of these monitoring systems comes from Brazil itself: the Ministry of Science, Technology and Innovation maintains the Previr Network, which assesses the presence of pathogens in various natural reserves in the country.

“As of last year, we started to monitor migratory wild birds. As H5N1 reached other parts of South America, there is a very high risk of finding it in Brazil as well”, says Durigon, who is part of the project.

It is worth noting that this version of influenza has not yet been detected in the country so far.

The Ministry of Agriculture and Livestock also performs constant analyzes on the farms.

“And this is strategic, since our country is one of the biggest chicken exporters in the world. If H5N1 arrives here and affects local producers, with the need to slaughter the animals, that would represent a big problem for the economy”, he adds. the ICB-USP virologist.

In addition to constant surveillance, another key action in this context is to create and test ways to prevent and treat avian flu.

In this area, the news is positive. “The antiviral drugs that we have available are effective against H5N1 in circulation”, points out Ferreira.

Vaccines against this influenza are also already under development. In Brazil, the Butantan Institute announced at the beginning of March that it is already working on an immunizer against this pathogen.

“The expectation is to finish the pre-clinical tests later this year and move on to the clinical study [que envolve voluntários humanos] in 2024”, says the institution in a note published on the website.

Siqueira estimates that, given the contingency plans drawn up in recent decades, it would be possible to have vaccine doses against H5N1 ready for large-scale campaigns in five or six months.

“We don’t know if this virus will cause a pandemic in 1, 5 or 100 years. But we need to be prepared for that”, says the expert.

From an individual standpoint, there are some basic measures you can already put in place to protect yourself — and lower your risk of a future pandemic.

“The most important care at this moment is not to touch or get close to a dead bird that you see on the beach, in the woods or anywhere”, guides Siqueira.

In these cases, the recommendation is to notify the local authorities, who may send employees with protective equipment to carry out the removal and send the body for laboratory analysis.

And, of course, the basic protocols of hand hygiene and staying away from activities if you have symptoms of a respiratory infection continue to apply.

“This is something that was reinforced in the Covid-19 pandemic and that we will need to maintain for the rest of our lives”, concludes the FioCruz microbiologist.

This text was published on the BBC News Brasil website.