Global dynamics of highly pathogenic avian influenza outbreaks between 2005 and 2016 - Focus on distance and rate of spread

Authors: AWADA, L - World Organization For Animal Health; TIZZANI, P - World Organization For Animal Health; Noh, Susan; DUCROT, C - Cirad, France; NTSAMA, F - World Organization For Animal Health; CACERES, P - World Organization For Animal Health; CHALVET-MONFRAY, K - Inland Northwest Research Alliance, Inra

Submitted to: Transboundary and Emerging Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2018
Publication Date: 8/27/2018
Citation: Awada, L., Tizzani, P., Noh, S.M., Ducrot, C., Ntsama, F., Caceres, P., Chalvet-Monfray, K. 2018. Global dynamics of highly pathogenic avian influenza outbreaks between 2005 and 2016 - Focus on distance and rate of spread. Transboundary and Emerging Diseases. 65(6):2006-2016. https://doi.org/10.1111/tbed.12986.
DOI: https://doi.org/10.1111/tbed.12986

Interpretive Summary: Highly pathogenic avian influenza (HPAI) is a major global health challenge due to heavy morbidity and mortality in domestic poultry as well as the necessity for implementation of strict disease control measures to prevent transmission of this potentially zoonotic virus to humans. However, prevention and control of avian influenza is particularly challenging due to its complex biology and epidemiology. The goal of this study was better understand the epidemiology of HPAI at a global level. Using data from 199 countries between 2005 and 2017we determined that: 1) Two major global peaks in the number of countries affected by HPAI occurred, one in 2006 and one in 2016. 2) Transmission of this disease is the lowest in September, begins to rise in October and peaks in February. 4) The median distance HPAI outbreaks spread in domestic and wild bird populations was 100 km and 222 km, respectively, while the median speed of outbreaks in domestic birds was 1.6 km/day and in wild birds was 6.5 km/day. 5) The distance of farm-to-farm transmission of HPAI in domestic birds was significantly negatively correlated with the number of outbreaks during the same time period, indicating that the spread of HPAI in domestic birds was lower during global pandemics than during periods of stable or low transmission. These findings will aid veterinary services throughout the world in designing and implementing effective programs to minimize the impacts of this disease.

Technical Abstract: Highly Pathogenic Avian Influenza (HPAI) is of major importance for human and animal health because of high morbidity and mortality in domestic poultry and the potential for transmission of this zoonotic pathogen to humans. Knowledge of HPAI epidemiology in avian populations is important in order to enhance the capacity of predicting and managing epidemics to minimize the negative impacts on human and animal health. Using data reported to the World Organisation for Animal Health between 2005 and 2017 by 199 countries for 15,966 outbreaks, we used a spatial and time-series analysis to determine: 1) That during the last 12 years, there were two major global peaks in the number of countries affected by HPAI with 33% and 26% of countries affected in 2006 and 2016. 2) Based on the seasonality analysis, transmission is the lowest in September, begins to rise in October and peaks in February. 3) The median distance HPAI outbreaks spread in domestic and wild bird populations was 100 km and 222 km, respectively, while the median rate of spread of outbreaks was 1.6 km/day in domestic birds and 6.5 km/day in wild birds. 4) The distance of farm-to-farm transmission of HPAI in domestic birds was significantly negatively correlated with the number of outbreaks during the same time period, indicating that the spread of HPAI in domestic birds was lower during global pandemics than during periods of stable transmission. These findings are of major importance for veterinary services to design and implement surveillance measures for improving preparedness to minimize the impacts of this disease.