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Bird flu has been detected in a pig in the US. Why does that matter?

David MG/Shutterstock

C Raina MacIntyre, UNSW Sydney and Haley Stone, UNSW Sydney

The United States Department of Agriculture last week reported that a pig on a backyard farm in Oregon was infected with bird flu.

As the bird flu situation has evolved, we’ve heard about the A/H5N1 strain of the virus infecting a range of animals, including a variety of birds, wild animals and dairy cattle.

Fortunately, we haven’t seen any sustained spread between humans at this stage. But the detection of the virus in a pig marks a worrying development in the trajectory of this virus.

How did we get here?

The most concerning type of bird flu currently circulating is clade 2.3.4.4b of A/H5N1, a strain of influenza A.

Since 2020, A/H5N1 2.3.4.4b has spread to a vast range of birds, wild animals and farm animals that have never been infected with bird flu before.

While Europe is a hotspot for A/H5N1, attention is currently focused on the US. Dairy cattle were infected for the first time in 2024, with more than 400 herds affected across at least 14 US states.

Bird flu has enormous impacts on farming and commercial food production, because infected poultry flocks have to be culled, and infected cows can result in contaminated diary products. That said, pasteurisation should make milk safe to drink.

While farmers have suffered major losses due to H5N1 bird flu, it also has the potential to mutate to cause a human pandemic.

Birds and humans have different types of receptors in their respiratory tract that flu viruses attach to, like a lock (receptors) and key (virus). The attachment of the virus allows it to invade a cell and the body and cause illness. Avian flu viruses are adapted to birds, and spread easily among birds, but not in humans.

So far, human cases have mainly occurred in people who have been in close contact with infected farm animals or birds. In the US, most have been farm workers.

The concern is that the virus will mutate and adapt to humans. One of the key steps for this to happen would be a shift in the virus’ affinity from the bird receptors to those found in the human respiratory tract. In other words, if the virus’ “key” mutated to better fit with the human “lock”.

A recent study of a sample of A/H5N1 2.3.4.4b from an infected human had worrying findings, identifying mutations in the virus with the potential to increase transmission between human hosts.

Why are pigs a problem?

A human pandemic strain of influenza can arise in several ways. One involves close contact between humans and animals infected with their own specific flu viruses, creating opportunities for genetic mixing between avian and human viruses.

Pigs are the ideal genetic mixing vessel to generate a human pandemic influenza strain, because they have receptors in their respiratory tracts which both avian and human flu viruses can bind to.

This means pigs can be infected with a bird flu virus and a human flu virus at the same time. These viruses can exchange genetic material to mutate and become easily transmissible in humans.

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Interestingly, in the past pigs were less susceptible to A/H5N1 viruses. However, the virus has recently mutated to infect pigs more readily.

In the recent case in Oregon, A/H5N1 was detected in a pig on a non-commercial farm after an outbreak occurred among the poultry housed on the same farm. This strain of A/H5N1 was from wild birds, not the one that is widespread in US dairy cows.

The infection of a pig is a warning. If the virus enters commercial piggeries, it would create a far greater level of risk of a pandemic, especially as the US goes into winter, when human seasonal flu starts to rise.

How can we mitigate the risk?

Surveillance is key to early detection of a possible pandemic. This includes comprehensive testing and reporting of infections in birds and animals, alongside financial compensation and support measures for farmers to encourage timely reporting.

Strengthening global influenza surveillance is crucial, as unusual spikes in pneumonia and severe respiratory illnesses could signal a human pandemic. Our EPIWATCH system looks for early warnings of such activity, which can speed up vaccine development.

If a cluster of human cases occurs, and influenza A is detected, further testing (called subtyping) is essential to ascertain whether it’s a seasonal strain, an avian strain from a spillover event, or a novel pandemic strain.

Early identification can prevent a pandemic. Any delay in identifying an emerging pandemic strain enables the virus to spread widely across international borders.

Australia’s first human case of A/H5N1 occurred in a child who acquired the infection while travelling in India, and was hospitalised with illness in March 2024. At the time, testing revealed Influenza A (which could be seasonal flu or avian flu), but subtyping to identify A/H5N1 was delayed.

This kind of delay can be costly if a human-transmissible A/H5N1 arises and is assumed to be seasonal flu because the test is positive for influenza A. Only about 5% of tests positive for influenza A are subtyped further in Australia and most countries.

In light of the current situation, there should be a low threshold for subtyping influenza A strains in humans. Rapid tests which can distinguish between seasonal and H5 influenza A are emerging, and should form part of governments’ pandemic preparedness.

A higher risk than ever before

The US Centers for Disease Control and Prevention states that the current risk posed by H5N1 to the general public remains low.

But with H5N1 now able to infect pigs, and showing worrying mutations for human adaptation, the level of risk has increased. Given the virus is so widespread in animals and birds, the statistical probability of a pandemic arising is higher than ever before.

The good news is, we are better prepared for an influenza pandemic than other pandemics, because vaccines can be made in the same way as seasonal flu vaccines. As soon as the genome of a pandemic influenza virus is known, the vaccines can be updated to match it.

Partially matched vaccines are already available, and some countries such as Finland are vaccinating high-risk farm workers.

C Raina MacIntyre, Professor of Global Biosecurity, NHMRC L3 Research Fellow, Head, Biosecurity Program, Kirby Institute, UNSW Sydney and Haley Stone, Research Associate, Biosecurity Program, Kirby Institute & CRUISE lab, Computer Science and Engineering, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

What Trump can do to reverse US climate policy − and what he probably can’t change

Donald Trump tours a liquefied natural gas terminal under construction in Louisiana in 2019. AP Photo/Evan Vucci

Gautam Jain, Columbia University

As the U.S. prepares for another Trump administration, one area unambiguously in the incoming president’s crosshairs is climate policy.

Although he has not released an official climate agenda, Donald Trump’s playbook from his last stint in the Oval Office and his frequent complaints about clean energy offer some clues to what’s ahead.

Exiting the Paris climate agreement

Less than six months into his first presidency, Trump in 2017 formally announced that he was withdrawing the United States from the Paris climate accord – the 2015 international agreement signed by nearly every country as a pledge to work toward keeping rising temperatures and other impacts of climate change in check.

This time, a greater but underappreciated risk is that Trump will not stop at the Paris Agreement.

In addition to exiting the Paris Agreement again, Trump could try to withdraw the United States from the United Nations Framework Convention on Climate Change. The 1992 treaty is the foundation for international climate talks. A withdrawal from that treaty would make it nearly impossible for a future administration to reenter the UNFCCC treaty because doing so would require the consent of two-thirds of the Senate.

The reverberation of such a step would be felt around the world. While the Paris Agreement is not legally binding and is based on trust and leadership, the stance taken by the world’s largest economy affects what other countries are willing to do.

It would also hand the climate leadership mantle to China.

U.S. funding to help other countries scale up clean energy and adapt to climate change rose significantly during the Biden administration. The first U.S. International Climate Finance Plan provided US$11 billion in 2024 to help emerging and developing economies. And commitments from the U.S. International Development Finance Corporation surged to almost $14 billion in the first two years of Biden’s presidency, versus $12 billion during the four years of Trump. Biden also pledged $3 billion to the United Nations’ Green Climate Fund.

Under President Trump, all these efforts will likely be scaled back again.

Targeting clean energy might not be so simple

In other areas, however, Trump may be less successful.

He has been vocal about rolling back clean energy policies. However, it may be harder for him to eliminate the Biden administration’s massive investments in clean energy, which are interwoven with much-needed investments in infrastructure and manufacturing in the Infrastructure Investment and Jobs Act and the Inflation Reduction Act.

Since both are laws that Congress passed, Trump would need majorities in both Houses to repeal them.

Even if Republicans end up with a trifecta – controlling both houses of Congress and the White House – repealing these laws will be challenging. That’s because the laws’ benefits are flowing heavily to red states. Trump’s allies in the oil and gas industry also benefit from the law’s tax credits for carbon capture, advanced biofuels and hydrogen.

However, while the Inflation Reduction Act may not be repealed, it will almost certainly be tweaked. The tax credit to consumers who buy electric vehicles is likely on the chopping block, as is the EPA regulation tightening tailpipe pollution standards, making battery-powered cars uneconomical for many.

Trump may also slow the work of the Department of Energy’s Loan Program Office, which has helped boost several clean energy industries. Again, this is not a surprise – he did it in the first term – except that the impact would be greater given that the office’s lending capacity has since skyrocketed to over $200 billion, thanks to the Inflation Reduction Act. So far, only about a quarter of the total has been doled out, so there is a rush to ramp up the pace before the new administration starts in January.

Drill, baby, drill?

Trump also talks about increasing fossil fuel production, and he almost certainly will take steps to boost the industry via deregulation and opening up more federal lands for drilling. But prospects of massively ramping up oil and gas production seem dim.

The United States is already producing more crude oil than any country ever. Oil and gas companies are buying back stocks and paying dividends to shareholders at a record pace, which they wouldn’t do if they saw better investment opportunities.

The futures curve indicates lower oil prices ahead, which could be further weighed down by slowing demand from any resulting economic weakness if Trump follows through on his threat to impose tariffs on all imports, leading to the risk of lower profitability.

Trump will likely try to roll back climate policies related to fossil fuels and emissions, which are the leading source of climate change, as he did with dozens of policies in his first administration.

That includes eliminating a new federal charge for methane emissions from certain facilities – the first attempt by the U.S. government to impose a fee or tax on greenhouse gas emissions. Methane is the primary component of natural gas and a potent greenhouse gas.

Trump has also promised to support approvals of new liquefied natural gas, or LNG, export terminals, which the Biden administration tried to pause and is still working to slow down.

The markets have a say in clean energy’s future

One clean energy source that Trump is likely to rally behind is nuclear energy.

And despite his criticism of wind and solar power, investments in renewable energy will likely continue rising because of market dynamics, especially with onshore wind and utility-scale solar projects becoming more cost effective than coal or gas.

Nevertheless, a U.S. withdrawal from the Paris Agreement and the regulatory and policy uncertainty under Trump would likely slow the pace of investments. The expected inflationary impact of his economic policies is likely to negate the benefits of lower cost of capital that were expected to flow through with central banks lowering interest rates this year. It’s an outcome that the warming planet can ill afford.

Gautam Jain, Senior Research Scholar in Financing the Energy Transition, Columbia University

This article is republished from The Conversation under a Creative Commons license. Read the original article.