The United States’ Centers for Disease Control and Prevention (CDC) has issued a health alert after the first case of H5N1 avian influenza, or bird flu, seemingly spread from a cow to a human.

A farm worker in Texas contracted the virus amid an outbreak in dairy cattle. This is the second human case in the US; a poultry worker tested positive in Colorado in 2022.

The virus strain identified in the Texan farm worker is not readily transmissible between humans and therefore not a pandemic threat. But it’s a significant development nonetheless.

Some background on bird flu

There are two types of avian influenza: highly pathogenic or low pathogenic, based on the level of disease the strain causes in birds. H5N1 is a highly pathogenic avian influenza.

H5N1 first emerged in 1997 in Hong Kong and then China in 2003, spreading through wild bird migration and poultry trading. It has caused periodic epidemics in poultry farms, with occasional human cases.

Influenza A viruses such as H5N1 are further divided into variants, called clades. The unique variant causing the current epidemic is H5N1 clade 2.3.4.4b, which emerged in late 2020 and is now widespread globally, especially in the Americas.

In the past, outbreaks could be controlled by culling of infected birds, and H5N1 would die down for a while. But this has become increasingly difficult due to escalating outbreaks since 2021.

Wild animals are now in the mix

Waterfowl (ducks, swans and geese) are the main global spreaders of avian flu, as they migrate across the world via specific routes that bypass Australia. The main hub for waterfowl to migrate around the world is Quinghai lake in China.

But there’s been an increasing number of infected non-waterfowl birds, such as true thrushes and raptors, which use different flyways. Worryingly, the infection has spread to Antarctica too, which means Australia is now at risk from different bird species which fly here.

H5N1 has escalated in an unprecedented fashion since 2021, and an increasing number of mammals including sea lions, goats, red foxes, coyotes, even domestic dogs and cats have become infected around the world.

Wild animals like red foxes which live in peri-urban areas are a possible new route of spread to farms, domestic pets and humans.

Dairy cows and goats have now become infected with H5N1 in at least 17 farms across seven US states.

What are the symptoms?

Globally, there have been 14 cases of H5N1 clade 2.3.4.4b virus in humans, and 889 H5N1 human cases overall since 2003.

Previous human cases have presented with a severe respiratory illness, but H5N1 2.3.4.4b is causing illness affecting other organs too, like the brain, eyes and liver.

For example, more recent cases have developed neurological complications including seizures, organ failure and stroke. It’s been estimated that around half of people infected with H5N1 will die.

The case in the Texan farm worker appears to be mild. This person presented with conjunctivitis, which is unusual.

Food safety

Contact with sick poultry is a key risk factor for human infection. Likewise, the farm worker in Texas was likely in close contact with the infected cattle.

The CDC advises pasteurised milk and well cooked eggs are safe. However, handling of infected meat or eggs in the process of cooking, or drinking unpasteurised milk, may pose a risk.

Although there’s no H5N1 in Australian poultry or cattle, hygienic food practices are always a good idea, as raw milk or poorly cooked meat, eggs or poultry can be contaminated with microbes such as salmonella and E Coli.

If it’s not a pandemic, why are we worried?

Scientists have feared avian influenza may cause a pandemic since about 2005. Avian flu viruses don’t easily spread in humans. But if an avian virus mutates to spread in humans, it can cause a pandemic.

One concern is if birds were to infect an animal like a pig, this acts as a genetic mixing vessel. In areas where humans and livestock exist in close proximity, for example farms, markets or even in homes with backyard poultry, the probability of bird and human flu strains mixing and mutating to cause a new pandemic strain is higher.

The cows infected in Texas were tested because farmers noticed they were producing less milk. If beef cattle are similarly affected, it may not be as easily identified, and the economic loss to farmers may be a disincentive to test or report infections.

How can we prevent a pandemic?

For now there is no spread of H5N1 between humans, so there’s no immediate risk of a pandemic.

However, we now have unprecedented and persistent infection with H5N1 clade 2.3.4.4b in farms, wild animals and a wider range of wild birds than ever before, creating more chances for H5N1 to mutate and cause a pandemic.

Unlike the previous epidemiology of avian flu, where hot spots were in Asia, the new hot spots (and likely sites of emergence of a pandemic) are in the Americas, Europe or in Africa.

Pandemics grow exponentially, so early warnings for animal and human outbreaks are crucial. We can monitor infections using surveillance tools such as our EPIWATCH platform.

The earlier epidemics can be detected, the better the chance of stamping them out and rapidly developing vaccines.

Although there is a vaccine for birds, it has been largely avoided until recently because it’s only partially effective and can mask outbreaks. But it’s no longer feasible to control an outbreak by culling infected birds, so some countries like France began vaccinating poultry in 2023.

For humans, seasonal flu vaccines may provide a small amount of cross-protection, but for the best protection, vaccines need to be matched exactly to the pandemic strain, and this takes time. The 2009 flu pandemic started in May in Australia, but the vaccines were available in September, after the pandemic peak.

To reduce the risk of a pandemic, we must identify how H5N1 is spreading to so many mammalian species, what new wild bird pathways pose a risk, and monitor for early signs of outbreaks and illness in animals, birds and humans. Economic compensation for farmers is also crucial to ensure we detect all outbreaks and avoid compromising the food supply.

C Raina MacIntyre, Professor of Global Biosecurity, NHMRC L3 Research Fellow, Head, Biosecurity Program, Kirby Institute, UNSW Sydney; Ashley Quigley, Senior Research Associate, Global Biosecurity, UNSW Sydney; Haley Stone, PhD Candidate, Biosecurity Program, Kirby Institute, UNSW Sydney; Matthew Scotch, Associate Dean of Research and Professor of Biomedical Informatics, College of Health Solutions, Arizona State University, and Rebecca Dawson, Research Associate, The Kirby Institute, UNSW Sydney

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

The fire at a major oil refinery in the Victorian city of Geelong has now reportedly been extinguished. But with thick smoke from the blaze lingering in the air on Thursday, many residents in Geelong and surrounding areas will understandably be worried.

What is released into the air when a refinery burns? And is the smoke bad for your health?

For most people, serious long-term health effects are unlikely. However, there can be short-term risks, and some groups are more vulnerable than others. So here’s what to look out for and how to stay safe.

What is in the air when an oil refinery burns?

Smoke from an oil refinery fire is made up of many different pollutants. The exact mix depends on what material is burning, how hot the fire is, and how long it lasts.

Typically, these fires release fine particles, known as PM2.5 and PM10, which are small enough to travel deep into the lungs.

They can also release toxic gases such as sulfur dioxide, nitrogen oxides and carbon monoxide, along with volatile organic compounds including benzene.

For people living further from the fire, fine particles are typically the main concern because they can travel long distances and linger in the air.

What are the health risks?

For most healthy adults living in the area, short-term exposure to these pollutants will cause irritation rather than lasting harm.

You may notice sore or watery eyes, a scratchy throat, coughing, headaches or a feeling of chest tightness. These symptoms are unpleasant but usually settle once air quality improves and exposure is reduced.

This kind of exposure is very different from the long-term occupational exposure experienced by refinery workers or emergency responders, for whom risks of cancer and lung diseases are much higher and better studied.

Who is most at risk?

When air quality worsens, people with existing lung conditions such as asthma or chronic obstructive pulmonary disease are more likely to experience symptom flare-ups.

Smoke particles can irritate already inflamed airways, leading to increased breathlessness and coughing. For those with existing respiratory conditions, this may mean needing to use reliever medications more frequently than normal.

Those with heart disease are also at greater risk as air pollution can place extra strain on the cardiovascular system, increasing the risk of chest pain, irregular heartbeat and heart failure.

Older people are also generally more sensitive to poor air quality because they are more likely to have chronic diseases and their heart and lungs might not work as well as they did when they were young.

Children have the greatest risk of developing health issues in the longer term, as their lungs are still developing. But the risks from an isolated exposure, such as the Geelong fire, are relatively low.

Some studies suggest repeated or prolonged exposure to air pollution during pregnancy may increase the likelihood of adverse outcomes for babies, such as low birth weight. But again, the risk for pregnant people from an isolated incident such as this is low.

These kind of events often make people worry about cancer risk. But based on what we know, being exposed in the short term, from a single fire, does not meaningfully increase your risk of developing cancer – though these kinds of events are difficult to study, so evidence remains limited.

Cancers associated with oil refinery emissions are linked to years or decades of exposure, usually among workers and those in heavily polluted environments.

So while monitoring the air pollution and for any health issues is still necessary, it’s important to keep the risk in perspective.

Continued follow-up of workers directly involved in firefighting or cleanup will be essential, as their exposure levels are likely to be much higher than those in the surrounding community.

How to protect yourself from smoke

There are practical steps people can take to reduce their exposure if smoke or poor air quality persists.

It sounds obvious, but the less time you spend outside in smoke, the lower your risk of health issues cause by smoke inhalation.

Staying indoors with windows and doors closed can significantly reduce your exposure to particles, especially if air conditioning is set to recirculate indoor air.

If you have asthma or other chronic lung diseases, it’s important to keep your reliever close at hand, follow your existing written action plan, and seek medical advice early if symptoms worsen. This can prevent more serious flare-ups.

Well-fitting P2 or N95 masks can reduce inhalation of fine particles when worn correctly. Loose-fitting surgical or cloth masks provide much less protection against smoke.

Residents in and around Geelong concerned about air quality can check real-time monitoring data for the area at the Victorian Environment Protection Authority website.

If your symptoms worsen or persist, you should speak to a health-care professional, and in emergency always call triple 0.

Brian Oliver, Professor, School of Life Sciences, University of Technology Sydney and Peter J. Irga, Assistant Professor (Senior Lecturer) in Air and Noise Pollution, University of Technology Sydney

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