Epidemiological Risk Factors for Animal Influenza A Viruses Overcoming Species Barriers

Abstract

Drivers and risk factors for Influenza A virus transmission across species barriers are poorly understood, despite the ever present threat to human and animal health potentially on a pandemic scale. Here we review the published evidence for epidemiological risk factors associated with influenza viruses transmitting between animal species and from animals to humans. A total of 39 papers were found with evidence of epidemiological risk factors for influenza virus transmission from animals to humans; 18 of which had some statistical measure associated with the transmission of a virus. Circumstantial or observational evidence of risk factors for transmission between animal species was found in 21 papers, including proximity to infected animals, ingestion of infected material and potential association with a species known to carry influenza virus. Only three publications were found which presented a statistical measure of an epidemiological risk factor for the transmission of influenza between animal species. This review has identified a significant gap in knowledge regarding epidemiological risk factors for the transmission of influenza viruses between animal species.

Protective Measures for Humans against Avian Influenza A(H5N8) Outbreaks in 22 European Union/European Economic Area Countries and Israel, 2016–17

“…The reasons for this finding might be related to the need for a minimum level of PPE and use of antiviral drugs, although another useful potential factor is likely to be the poor ability of the virus to be transmitted to humans. Finally, a thorough review of the measures recommended during these outbreaks in view of the results of our survey might help to identify critical points and challenges in each country that can be addressed and resolved to be better prepared for future outbreaks ( 35 ). …”

Repeated vaccination against matched H3N2 influenza virus gives less protection than single vaccination in ferrets

“…1,2 In addition to these seasonal epidemics, novel influenza viruses that have not previously circulated among humans occasionally cross from animal reservoirs, leading to global pandemics in the naive population. 3 Annual influenza vaccination is the primary prevention strategy against seasonal influenza. In many countries, annual influenza vaccination is recommended only for high-risk individuals, whereas in the United States it is recommended for people 6 months of age and older without contraindications.…”

Human Susceptibility to Influenza Infection and Severe Disease

“…Health-care personnel are at increased risk of exposure to IAV as was shown during the 2009 A/H1N1 pandemic (Lietz et al 2016). Individuals who work in close contact with animals, such as birds and swine, may also have an increased risk of zoonotic transmission (Harris et al 2017;Root et al 2017). Although rare, the zoonotic emergence of novel IAV strains has resulted in some of the most widespread influenza virus outbreaks in history (Webster and Laver 1972;Taubenberger and Kash 2010).…”