Could Bird Flu Spread to Humans? Indian Scientists Shed Light!

Thu Dec 18 2025 12:32:47 GMT+0200 (Eastern European Standard Time)

Indian researchers unravel how H5N1 might jump from birds to humans, presenting warning signs and containment strategies to prevent a potential health crisis.

Scientists in India are modeling the spread of bird flu (H5N1) to humans, warning that a single infected bird can trigger a widespread outbreak. Current data highlights the importance of early interventions to prevent human-to-human transmission. While the immediate threat remains low, surveillance and quick responses are essential to mitigate risks, particularly in densely populated poultry areas. As cases increase, the study emphasizes the critical timing needed for effective containment measures before an outbreak spirals out of control.

For years, scientists have warned that bird flu - better known as H5N1 - could one day make the dangerous leap from birds to humans and trigger a global health crisis.

Avian flu, a type of influenza, is entrenched across South and South-East Asia and has occasionally infected humans since emerging in China in the late 1990s. From 2003 to August 2025, the World Health Organization (WHO) reported 990 human H5N1 cases across 25 countries, including 475 deaths - a 48% fatality rate.

In the US alone, the virus has struck more than 180 million birds, spread to over 1,000 dairy herds in 18 states, and infected at least 70 people - mostly farmworkers - causing several hospitalizations and one death. In January, three tigers and a leopard died at a wildlife rescue center in India's Nagpur city from the virus that typically infects birds.

Symptoms in humans mimic a severe flu: high fever, cough, sore throat, muscle aches and, at times, conjunctivitis. Some people have no symptoms at all. The risk to humans remains low, but authorities are watching H5N1 closely for any shift that could make it spread more easily.

That concern is what prompted new peer-reviewed modeling by Indian researchers Philip Cherian and Gautam Menon of Ashoka University, which simulates how an H5N1 outbreak might unfold in humans and what early interventions could stop it before it spreads.

In other words, the model uses real-world data and computer simulations to play out how an outbreak might spread in real life. The threat of an H5N1 pandemic in humans is a genuine one, but we can hope to forestall it through better surveillance and a more nimble public-health response, Prof Menon told the BBC.

A bird flu pandemic, researchers say, would begin quietly: a single infected bird passing the virus to a human - most likely a farmer, market worker, or someone handling poultry. From there, the danger lies not in that first infection but in what happens next: sustained human-to-human transmission.

Because real outbreaks start with limited, messy data, the researchers turned to BharatSim, an open-source simulation platform originally built for Covid-19 modeling, but versatile enough to study other diseases.

The key takeaway for policymakers is how narrow the window for action can be before an outbreak spirals out of control, the researchers say. The paper estimates that once cases rise beyond roughly two to 10, the disease is likely to spread beyond primary and secondary contacts.

Primary contacts are people who have had direct, close contact with an infected person, while secondary contacts are those who have not met the infected person but have contact with them.

If households of primary contacts are quarantined when just two cases are detected, the outbreak can almost certainly be contained, the research found. However, by the time 10 cases are identified, the infection has likely already spread into the wider population, making further intervention much more difficult.

To model the situation, the researchers chose a synthetic village in Tamil Nadu, the heart of India's poultry industry. Here, they generated a model with households, workplaces, market spaces, and seeded it with infected birds to mimic real-life exposure.

The simulations highlighted the critical importance of timing for intervention. Culling of infected birds works best if executed before human infection. Afterward, isolating infected individuals and quarantining their households can be effective, but only until tertiary infections arise.

Real-time simulations like these can potentially aid public-health officials in determining the most effective actions in the critical early hours of an outbreak. Dr. Lakdawala warns that complacency would be a mistake, emphasizing the importance of preparation for a potential flu pandemic.