Scientists have identified global hotspots for avian flu where dense populations of people, cattle, and poultry overlap within a small share of the Earth's land.

These concentrated zones reshape where the virus is most likely to spread, persist, and cross between species.

On the new global map, the highest-risk zones sit where wetlands, farms, and dense human settlement press close together.

Using month-by-month bird records, researchers at the Chinese Academy of Sciences (CAS) showed why those overlaps keep returning repeatedly.

Instead of treating birds as static dots, the analysis followed where species stay, gather, and rotate through the year. That choice turned bird movement itself into the clue, setting up the paper's central claim about hidden exposure worldwide.

To build that map, the team created entropy, a score for month-to-month change, from 779 waterbird species worldwide.

Places scored higher when many waterbird species arrived, lingered, and then gave way to others over the year. That pattern matters because longer stays and heavier mixing give viruses more chances to persist, swap genes, and spread.

A map built from motion rather than presence can capture exposure better than older, flatter, more traditional risk screens.

Waterbirds matter as avian flu often circulates quietly in wild bird hosts before reaching barns, markets, or backyard flocks.

Human infection usually begins through close contact with infected animals or contaminated places, a point the World Health Organization fact sheet makes clear.

When wild birds and domestic animals share water, feed, or space, spillover, a virus crossing species, becomes more likely. That mechanism helps explain why the map shows higher risk where bird habitat and livestock production meet so closely.

Across global land, hotspot zones covered 14% and still matched avian flu patterns strongly in the study.

Its strongest signal appeared with H5N1, a fast-moving avian flu strain, and the model scored 0.87 on a standard accuracy scale.

That level did not mean every outbreak was predictable, but it did show bird activity tracks real-world risk closely.

Once the researchers had that fit, they could ask where the danger concentrates most and who lives there.

Four places stood out most clearly on the map: the United States, the European Union, China, and India.

Within those hotspot areas, the authors counted 52% of exposed people, 41% of cattle, and 51% of poultry.

That overlap matters as dense farms keep the virus near mammals and poultry, while dense settlement keeps many people nearby. A small slice of land can therefore hold a surprisingly large slice of the world's exposure risk.

Sub-Saharan Africa carried one of the study's sharpest warnings, even though official case reports stayed very low.

The map marked more than 740 million acres there, about 15% of all hotspot land worldwide.

Yet the same region accounted for less than 1% of reported global cases, creating a glaring mismatch.

Low reporting in a high-risk zone can hide spread, leaving health agencies reactive instead of ready in advance.

Maps that show where birds, farms, and people overlap can narrow the places needing the fastest health response. A risk map like this works best as an early filter, not as a precise outbreak forecast. It can steer testing toward wetlands beside farms, live bird markets, migration stopovers, and nearby worker communities.

As the signal comes from bird movement, officials could refresh surveillance before seasonal mixing peaks each year.

Better targeting matters most where budgets are thin and missing one outbreak can trigger much larger economic losses.

No map can tell officials exactly when the next farm or person will become infected. Case reports are uneven, wildlife records are patchy in some places, and farm biosecurity still changes outcomes.

Hotspots mark higher exposure odds, not certainty, so some flagged areas may stay quiet for long periods.

Even with those limits, the approach offers something older outbreak maps often lacked: movement-based ecological context.

The study treats migrating waterbirds as a measurable warning system for farms, cattle, and people worldwide.

If health agencies pair that map with faster testing and stronger reporting, more outbreaks may be found before they spread.

The study is published in Nature.

- earth.com

Scientists identify global hotspots for avian flu

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