Abstract
Influenza pandemics can emerge unexpectedly and wreak global devastation. However, each of the six pandemics since 1889 emerged in the Northern Hemisphere just after the flu season, suggesting that pandemic timing may be predictable. Using a stochastic model fit to seasonal flu surveillance data from the United States, we find that seasonal flu leaves a transient wake of heterosubtypic immunity that impedes the emergence of novel flu viruses. This refractory period provides a simple explanation for not only the spring-summer timing of historical pandemics, but also early increases in pandemic severity and multiple waves of transmission. Thus, pandemic risk may be seasonal and predictable, with the accuracy of pre-pandemic and real-time risk assessments hinging on reliable seasonal influenza surveillance and precise estimates of the breadth and duration of heterosubtypic immunity.
Highlights
Influenza pandemics have emerged regularly throughout the 20th and 21st centuries, resulting in significant morbidity and mortality [1]
The risk of pandemic emergence should be high during the flu season, when viruses are abundant and conditions favor transmission
The six pandemics on record since 1889 all emerged in the Northern Hemisphere following the flu season, suggesting that other forces may predictably constrain pandemic risk
Summary
We developed a stochastic two-strain influenza transmission model that incorporates contact network structure, heterosubtypic immunity, and new estimates of the seasonal flu reproduction number to investigate the dynamics of pandemic emergence risk. Exposed-Infectious-Protected-Recovered) network model similar to [58] (S1 Fig). Upon infection with one strain, individuals progress through the Exposed and Infectious classes; upon recovery, they enter a short period of complete protection from infection by the other strain, after which they regain full susceptibility to that strain. Close sequential infections can occur in the model, as some individuals transition through the protected class almost immediately (S2 Fig). We modeled single influenza seasons, and assumed that recovered individuals are fully and permanently immune to their infecting strain, that there are no births or deaths, and that the network structure does not change over the course of a single simulation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
