Which infectious disease is expected to be the most significant emerging threat in 2025?

COVID-19 emerged unexpectedly, spread quickly, and claimed millions of lives worldwide. Since then, it’s fair to say that many people have been concerned about the next major infectious disease, whether it’s a virus, bacterium, fungus, or parasite.

With COVID-19 in retreat thanks to highly effective vaccines, the three infectious diseases causing the greatest concern among public health officials are malaria (a parasite), HIV (a virus), and tuberculosis (a bacterium). These diseases together claim around 2 million lives annually.

In addition, there are pathogens on priority watchlists, particularly those resistant to treatments like antibiotics and antivirals. Scientists also remain vigilant for potential new threats. While any pathogen could pose a risk, certain types are more likely to cause rapid outbreaks, including influenza viruses.

One such virus currently raising alarms is the H5N1 influenza A subtype, also known as bird flu. This virus is widespread among wild and domestic birds, such as poultry, and has recently been detected in dairy cattle in several US states and in horses in Mongolia. As animal cases rise, concerns grow that the virus could jump to humans. Already, 61 human cases have been reported in the US this year, primarily among farm workers exposed to infected cattle or through consumption of raw milk. This is a significant increase compared to only two cases in the Americas in the previous two years. With a 30% mortality rate from human infections, bird flu is becoming a major concern for public health officials.

Fortunately, H5N1 doesn’t seem to spread from person to person, which lowers the risk of a human pandemic. Influenza viruses must attach to specific molecular structures on the surface of cells to enter and replicate. Human-adapted flu viruses can easily bind to human receptors, enabling them to spread among people. Bird flu, however, is better suited to bird receptors and has difficulty binding to human receptors. As a result, it doesn’t spread easily between humans in its current form.

However, a recent study showed that a single mutation in the virus could make H5N1 capable of human-to-human transmission, potentially triggering a pandemic. If this occurs, governments must act swiftly to contain the spread. Disease control centers around the world have already developed pandemic preparedness plans for bird flu and other emerging diseases. For instance, the UK has secured 5 million doses of an H5 vaccine to protect against bird flu in preparation for potential risks in 2025.

Even if H5N1 does not evolve to spread easily between humans, it is likely to continue affecting animal health in 2025, with significant animal welfare, food supply, and economic implications.

Everything is interconnected. This concept is part of the “One Health” approach, which views human, animal, and environmental health as intertwined, with each impacting the others equally. By studying and preventing diseases in our environment and animal populations, we can better prepare for and mitigate the risk of these diseases spilling over into humans. Similarly, by monitoring and addressing infectious diseases in humans, we also protect the health of animals and the environment. However, we must not overlook the ongoing “slow pandemics” affecting humans, such as malaria, HIV, tuberculosis, and other pathogens. Addressing these issues remains crucial, alongside staying vigilant for any emerging diseases on the horizon.