The evolution and future of influenza pandemic preparedness

Abstract

The influenza virus is a global threat to human health causing unpredictable yet recurring pandemics, the last four emerging over the course of a hundred years. As our knowledge of influenza virus evolution, distribution, and transmission has increased, paths to pandemic preparedness have become apparent. In the 1950s, the World Health Organization (WHO) established a global influenza surveillance network that is now composed of institutions in 122 member states. This and other surveillance networks monitor circulating influenza strains in humans and animal reservoirs and are primed to detect influenza strains with pandemic potential. Both the United States Centers for Disease Control and Prevention and the WHO have also developed pandemic risk assessment tools that evaluate specific aspects of emerging influenza strains to develop a systematic process of determining research and funding priorities according to the risk of emergence and potential impact. Here, we review the history of influenza pandemic preparedness and the current state of preparedness, and we propose additional measures for improvement. We also comment on the intersection between the influenza pandemic preparedness network and the current SARS-CoV-2 crisis. We must continually evaluate and revise our risk assessment and pandemic preparedness plans and incorporate new information gathered from research and global crises.

Fig. 1. History of influenza pandemics.

There have been four influenza pandemics since the turn of the 20th century, occurring in 1918 (H1N1), 1957 (H2N2), 1968 (H3N2), and 2009 (H1N1). This timeline shows the temporal and genetic reassortment relationships among each of the pandemic influenza subtypes.

Fig. 2. Prepandemic influenza and preparedness.

A combined timeline indicating the temporal relationships between emerging potential pandemic strains (with accompanying animal reservoirs) and steps taken to improve pandemic preparedness. Dashed arrows indicate continuing outbreaks for each strain after they first emerged.

Fig. 3. Weighted risk assessment elements to estimate emergence and impact risks for prepandemic influenza strains.

Schematic graph indicating the relative weights that each of the risk elements defined by the IRAT and TIPRA contribute to the overall assessment scores for emergence and impact risk of an emergent influenza strain.

Fig. 4. Ideal pandemic response workflow.

A schematic workflow of the ideal pandemic response from prepandemic surveillance detection to widespread vaccine distribution.