COVID-19 surprised the world by appearing quickly, spreading fast, and causing many deaths. Since then, many people worry about the next big disease, whether it's a virus, bacteria, fungus, or parasite. Now that COVID is mostly under control due to strong vaccines, health officials are paying attention to other serious threats.

Diseases like malaria, HIV, and tuberculosis, which kill around 2 million people every year, remain a top priority. Meanwhile, health experts are keeping a close eye on potentially dangerous pathogens, especially those resistant to existing treatments. Among these, one influenza virus—H5N1, or bird flu—is causing serious concern for the near future.

Why bird flu is a growing threat

H5N1 bird flu is a virus that commonly affects wild and domestic birds like poultry. However, recently it has started appearing in other animals too. For instance, it has been found in dairy cattle in several US states and even in horses in Mongolia.

When diseases like bird flu spread more widely among animals, the risk of them jumping to humans increases. Bird flu can infect humans, and 61 cases have already been reported in the US this year. Most of these cases involve farm workers in contact with infected cattle or people drinking raw milk. This is a sharp rise compared to just two cases in the Americas over the last two years. What’s more alarming is the 30% mortality rate in human infections caused by bird flu, making it a high priority for public health officials.

Fortunately, H5N1 doesn’t currently spread from person to person. This is because it binds to specific molecular structures called sialic receptors found on the outside of cells. Bird flu viruses are better adapted to the receptors in birds and have difficulty attaching to those in humans, which reduces the chances of spreading among people.

However, a recent study warns that just a single mutation in the bird flu virus’s genome could make it capable of human-to-human transmission. If this happens, it could quickly trigger a pandemic.

Preparedness plans for the future

Governments and health organizations are preparing for such scenarios. For instance, the UK has already purchased 5 million doses of the H5 vaccine to be ready for 2025. Global pandemic preparedness plans for bird flu and other emerging diseases are being developed to address the risks effectively.

Even without the ability to spread between humans, bird flu could have significant impacts. It threatens animal health and welfare, and if outbreaks grow, they could disrupt food supplies and harm the economy.

Bird flu’s potential to impact both humans and animals highlights the importance of a “one health” approach. This means understanding how human, animal, and environmental health are interconnected. By preventing diseases in animals and the environment, we can better protect human health—and vice versa.

While keeping an eye on new diseases like H5N1, we must not ignore the ongoing fight against existing ones. Malaria (a parasite), HIV (a virus), and tuberculosis (a bacterium) continue to kill millions each year. Public health officials and scientists must work on multiple fronts: tackling these “slow pandemics” while also preparing for new threats.

As history has shown with COVID-19, an effective response requires rapid action, strong collaboration, and investments in science and healthcare. Keeping a close watch on diseases in animals and preventing their spread to humans is key to avoiding future pandemics.

By addressing challenges in human, animal, and environmental health together, we can better prepare for the unpredictable future of infectious diseases. Everything is connected, and understanding this is our best defense against the next big health crisis.