PoultryWorld: Astonishing speed of avian influenza transmission explored

New research has shown that most poultry entering live bird markets in Asia become infected with avian influenza within 24 hours if they remain there for a day.

The study found that more that 9 in 10 chickens entering live bird markets having been previous exposed to the H9N2 subtype of avian influenza virus become infected with it. Birds typically became contagious in less than five and a half hours.

The new research from the Global Challenges Research Fund’s (GCRF) One Health Poultry Hub, including researchers from the Royal Veterinary College (RVC) has, for the first time, modelled the transmission of avian influenza, revealing the speed at which it can spread in Asia’s live bird markets. The findings will help researchers evaluate the impact of potential control measures to reduce H9N2 (a subtype of avian influenza) in markets. One in 10 birds arriving at live bird markets are already exposed to the H9N2 virus.

Avian influenza virus variants

H9N2 is a zoonotic virus that is defined as low pathogenic and causes mild diseases that can lead to production losses for chicken farmers. Genes from H9N2 have, however, also been found in the emergence of new influenza virus variants, making it a potential pandemic threat with its first human infection reported in Vietnam in April 2024.

Published in Nature Communications, researchers from the RVC; University of Oxford; City University of Hong Kong, China; Chattogram Veterinary and Animal Sciences University, Bangladesh; and the French National Research Institute for Agriculture, Food and the Environment, used biological data obtained from chickens in live bird markets and a computer modelling system to determine the transmission rate.

These findings follow previous research from the GCRF One Health Poultry Hub, which has found that 2-3 in 10 chickens in live bird markets in Bangladesh and Vietnam test positive for H9N2.

Map and track avian influenza virus spread

Currently, veterinary public health interventions to limit and prevent the spread of the virus focus on addressing the disease in the markets, including banning the storage of birds overnight, enforcing market ‘rest days’ and separating bird species in the markets. The findings from this research, however, can now be used to inform the first-of-its-kind Epidemic Network Simulation in Poultry Transportation Systems (EPINEST) computer model to map and track avian influenza virus spread across time and space.

Dr Guillaume Fournié, a researcher at the RVC and INRAE, said: “Our research suggests that unless any practical measures designed to protect market traders and shoppers are complemented by interventions in the networks and supply chains that deliver the birds to market, they are unlikely to have enough impact. To be successful, a pandemic prevention strategy must also target chicken farmers and transporters in countries where the virus is endemic to reduce viral burden in markets. Our findings make a clear case for considering multipronged interventions, including vaccination strategies for all poultry destined for sale in live bird markets.”

The GCRF One Health Poultry Hub is funded by UK Research and Innovation through the GCRF. It is part of the UK’s Official Development Assistance, which is managed by the Department for Science, Innovation and Technology.