Indian Scientists Warn of Potential Bird Flu Jump to Humans
For years, scientists have sounded the alarm about the potential for bird flu – H5N1 – to jump to humans and trigger a global health crisis. Now, new modelling suggests the window to prevent a pandemic may be surprisingly narrow.
Avian flu has been firmly established in South and South-East Asia since its emergence in China in the late 1990s. The World Health Organisation (WHO) has, as of August 2025, reported 990 human cases across 25 countries, with a concerning 48% fatality rate – 475 deaths.
More recently, the virus has caused significant disruption in the US, affecting over 180 million birds and spreading to over 1,000 dairy herds in 18 states. At least 70 people, largely farmworkers, have been infected, with several hospitalised and one death reported. Even wildlife isn’t spared; in January, three tigers and a leopard succumbed to the virus at a wildlife rescue centre in India’s Nagpur city.
Symptoms in humans closely resemble those of severe influenza: high fever, cough, sore throat, muscle aches, and sometimes conjunctivitis. Importantly, some individuals may experience no symptoms at all. While the current risk to humans remains low, health authorities are closely monitoring H5N1 for any mutations that could enhance its transmissibility.
New research published in the BMC Public Health journal, conducted by Philip Cherian and Gautam Menon of Ashoka University in India, employs computer simulations to model how an H5N1 outbreak might unfold and pinpoint effective early interventions.
The study used BharatSim, a simulation platform originally designed for COVID-19 modelling, which has proven versatile enough to examine other diseases. Researchers created a synthetic village – a computer-generated community mimicking real-world characteristics – in Namakkal district, Tamil Nadu, a major poultry hub in India, comprising over 1,600 poultry farms and 70 million chickens producing over 60 million eggs daily.
The simulations reveal that swift action is crucial. Once cases exceed a small number – between two and ten – the virus is likely to spread beyond immediate and secondary contacts. Professor Menon, speaking to the BBC, emphasized that better surveillance and a proactive public-health response are vital to prevent a potential pandemic.
According to the research, quarantining the households of primary contacts when just two cases are identified can almost certainly contain the outbreak. However, delaying intervention until 10 cases are detected makes it overwhelmingly likely the infection will spread widely beyond control.
“The key takeaway for policymakers is how narrow the window for action can be before an outbreak spirals out of control,” the researchers state.
While culling infected birds is effective, it must be done before the virus jumps to humans. Isolating infected individuals and quarantining their households can halt the spread at its secondary stage but face challenges. Introducing quarantine too early risks prolonged family exposure and increased transmission within households, while delaying it renders the measure largely ineffective.
The simulations also suggest that targeted vaccination can help raise the threshold for sustained transmission, but offers limited immediate protection within households.
Virologist Seema Lakdawala of Emory University cautions that the model assumes highly efficient virus transmission, a factor that varies between strains. Emerging research also indicates that not all infected individuals are equally likely to spread the virus, echoing the “super-spreader” phenomenon observed during the COVID-19 pandemic. She believes an H5N1 pandemic, should it occur, would likely be more akin to the 2009 swine flu pandemic due to existing antiviral treatments and vaccine candidates.
However, Dr Lakdawala warned against complacency, noting that H5N1 could re-assort with existing flu strains, potentially leading to chaotic and unpredictable seasonal epidemics.
The researchers are continuing to refine their model, integrating real-time data and addressing factors like asymptomatic cases, to provide public-health officials with critical insights during the crucial early stages of an outbreak – helping them determine which interventions matter most before the opportunity for containment is lost.
Image Source: MYJOYONLINE
